content eq3 Flashcards
1
Q
- What is long-term sea level change?
A
It refers to changes in sea level occurring over thousands of years, driven by eustatic (global water volume) and isostatic (local land level) factors, as well as tectonics.
2
Q
- What are some short-term factors affecting sea level?
A
Tides, variations in surface air pressure, and winds pushing on the water surface create temporary bulges.
3
Q
- What is eustatic sea level change?
A
A global change in sea level caused by variations in the volume of water in the oceans due to ice formation/melting and thermal expansion or contraction.
4
Q
- How do Milankovitch Cycles influence eustatic change?
A
They cause cyclical changes in Earth’s orbit, leading to glacial (cold) and interglacial (warm) phases that transfer water between oceans and ice sheets.
5
Q
- What happens during a glacial period?
A
Ice sheets form as water from the oceans freezes onto land, reducing ocean volume and causing a global fall in sea level (marine regression).
6
Q
- How much lower were global sea levels during the most recent glacial period?
A
Sea levels were about 120 m lower than today, exposing areas like the English Channel, Irish Sea, and North Sea as dry land.
7
Q
- What occurs during an interglacial period?
A
Ice sheets shrink due to warmer temperatures, returning water to the oceans, which increases ocean volume and raises sea level (marine transgression).
8
Q
- How does thermal expansion contribute to sea level rise?
A
Rising water temperatures cause the ocean water to expand, increasing its volume and contributing to eustatic sea level rise.
9
Q
- What role does anthropogenic forcing play in sea level change?
A
Human activities, such as greenhouse gas emissions, accelerate interglacial warming and contribute to additional sea level rise.
10
Q
- By how much did global sea levels rise between 1870 and 2010?
A
Sea levels rose by approximately 21 cm during that period.
11
Q
- What is the predicted impact of melting Antarctic ice sheets?
A
They are predicted to raise global sea levels by up to 50 m over time.
12
Q
- What is an isostatic sea level change?
A
It is a local change in sea level resulting from the vertical movement of land, either rising or sinking.
13
Q
- What causes local land to rise in an isostatic change?
A
Post-glacial rebound (uplift) and accretion (deposition) can cause local land to rise, leading to a relative fall in sea level.
14
Q
- How does subsidence affect local sea level?
A
When land sinks due to factors like sediment loading or water table lowering, local sea level appears to rise.
15
Q
- What is post-glacial adjustment?
A
It is the process where the Earth’s crust rebounds upward after being depressed by the weight of ice sheets, while adjacent areas may subside.
16
Q
- How does post-glacial adjustment affect the UK?
A
Northern Britain is experiencing uplift (falling relative sea level at about 1.5 mm per annum) while southern Britain is subsiding (rising relative sea level at about 1 mm per annum).
17
Q
- What is the net sea level change at Land’s End in Cornwall?
A
Land’s End is sinking isostatically by about 1.1 mm per annum, compounded with a 2.8 mm per annum eustatic rise, totaling a 3.9 mm rise per annum.
18
Q
- How do sediment deposition processes in deltas influence isostatic change?
A
Deposition adds weight, causing slow crustal sag (subsidence) in delta regions, which can lead to a relative sea level rise.
19
Q
- How can lowering the water table contribute to subsidence?
A
Reduced pore water pressure from increased evaporation or water abstraction can cause sediments to settle, resulting in land subsidence.
20
Q
- What tectonic processes can influence long-term sea level change?
A
Uplift at constructive plate margins, subsidence from sea floor spreading, faulting (horst and graben formation), and volcanic activity.
21
Q
- How can rising magma at a constructive plate margin affect sea level?
A
It lifts the overlying crust, reducing the ocean basin capacity and causing a small eustatic sea level rise.
22
Q
- What is the effect of sea floor spreading on sea level?
A
As new, hot crust forms and then cools, it subsides; colder, denser crust occupies more space, potentially raising sea levels.
23
Q
- How can tectonics produce isostatic changes?
A
Tectonic processes like faulting can uplift horst blocks (lowering local sea level) or cause graben subsidence (raising local sea level).
24
Q
- What example illustrates tectonic uplift reducing ocean capacity?
A
Uplift of a crustal plate, such as in the Indian Ocean, can reduce capacity and produce a small global eustatic rise (~0.1 mm per annum).
25
25. How does volcanic activity lead to isostatic fall?
Deposition of lava or ash increases the weight on the crust, causing it to subside locally.
26
26. What impact does faulting have on local sea levels?
Uplifted horst blocks result in local sea level fall, while subsiding graben produce a relative sea level rise.
27
27. How did the Boxing Day Tsunami affect local land levels?
In 2004, crustal extension during the tsunami caused an isostatic fall of about 20 cm on the island of Sumatra.
28
28. What is meant by “marine regression”?
It is the exposure of the sea bed as land when global sea levels fall, typically during glacial periods.
29
29. What is “marine transgression”?
It is the flooding of low-lying land as sea levels rise, often during interglacial periods.
30
30. Why doesn't melting sea ice affect global sea levels?
Because floating ice displaces its own volume of water, so its melting does not change the overall sea level.
31
31. How do glacial cycles redistribute water between the ocean and land?
During glacials, water is stored as ice on land; during interglacials, melting returns water to the oceans, altering global sea level.
32
32. How does thermal expansion differ from ice melting in affecting sea level?
Thermal expansion increases water volume due to warming, while ice melting transfers water from land ice to the ocean, both contributing to sea level rise.
33
33. What is the primary driver of eustatic sea level fall during glacial periods?
The formation of extensive ice sheets locks water on land, reducing ocean volume and lowering sea level.
34
34. What is the primary driver of eustatic sea level rise during interglacial periods?
Melting ice sheets and thermal expansion return water to the ocean, raising sea level globally.
35
35. How do isostatic adjustments interact with eustatic changes?
Local land movements (uplift or subsidence) can either offset or exacerbate global sea level changes, creating variations along different coastlines.
36
36. Why might sea level fall in northern Britain despite global sea level rise?
Isostatic rebound (uplift) in northern Britain can exceed the global eustatic rise, resulting in a net sea level fall locally.
37
37. What is the “pivot” effect in the UK regarding sea level change?
The UK is experiencing uplift in the north and subsidence in the south, leading to contrasting local sea level changes.
38
38. How do human activities influence long-term sea level change?
Through greenhouse gas emissions (accelerating warming and ice melt) and coastal engineering (altering sediment supply and land subsidence).
39
39. What role does the sediment budget play in sea level change?
Sediment deposition (accretion) or erosion can alter local land elevation, contributing to isostatic changes in sea level.
40
40. How can coastal management mitigate impacts of sea level rise?
By managing sediment supply, reinforcing coastlines, and planning for potential subsidence or uplift to balance natural processes.
41
41. Why are long-term sea level changes described as a dynamic equilibrium?
Because, despite constant sediment and energy fluxes, inputs and outputs (eustatic, isostatic, and tectonic) eventually balance out over long periods.
42
42. How might future climate change impact long-term sea level change?
Increased global temperatures could accelerate ice melt and thermal expansion, further rising sea levels, while also potentially altering tectonic and isostatic responses.
43
1. What are emergent coastlines?
Emergent coastlines are formed when land previously under the sea is exposed due to a fall in relative sea level, often as a result of post-glacial isostatic rebound.
44
2. What are submergent coastlines?
Submergent coastlines form when rising sea levels flood areas that were once terrestrial, creating features such as rias, fjords, and Dalmatian coasts.
45
3. How did eustatic changes during the Devensian Glacial period affect sea level?
During the Devensian Glacial, sea levels fell by about 120 m, exposing parts of the continental shelf as dry land.
46
4. What happened at the start of the Holocene Interglacial in terms of sea level?
There was a rapid eustatic rise of about 100 m over roughly 1000 years as ice sheets and glaciers shrank, submerging many coastal areas.
47
5. How does post-glacial adjustment influence emergent coastlines?
Post-glacial isostatic rebound gradually raises formerly glaciated land, exposing relict coastal features like raised beaches and fossil cliffs.
48
6. What is a raised beach?
A raised beach is a relict beach, now above the high tide mark, often flat and covered with sand or rounded pebbles, and sometimes stabilized by plant succession.
49
7. What is a fossil cliff?
A fossil cliff is a steep slope formed by marine erosion (often displaying wave-cut notches, caves, or arches) that is now situated above the present high tide level.
50
8. How do raised beaches and fossil cliffs provide evidence of past sea levels?
They preserve features created by marine processes when sea level was higher, now left stranded on land due to isostatic uplift.
51
9. Give an example of an emergent coastline in the UK.
The Isle of Arran features raised beaches at different levels, indicating various stages of post-glacial sea level change.
52
10. How high is the raised beach on the Isle of Arran?
One raised beach is about 5 m above current sea level, with others at different elevations marking successive stages of emergence.
53
11. What is an example of a raised beach used for infrastructure?
At Lendalfoot in Ayrshire, a flat raised beach surface is used as a route for the A77 main road.
54
12. How far inland can fossil cliffs be found on emergent coastlines?
Fossil cliffs may lie tens to hundreds of metres inland from the current coastline, as seen at Lendalfoot with a 40 m raised cliff now 200 m inland.
55
13. What process leads to marine regression on emergent coasts?
A global fall in sea level (eustatic drop) due to glacial periods, combined with isostatic uplift, exposes former sea beds as emergent land.
56
14. How does isostatic rebound affect northern Britain?
Northern Britain is experiencing uplift at about 1.5 mm per annum, leading to a relative fall in sea level locally.
57
15. What contrasting isostatic behavior is observed in southern Britain?
Southern Britain is subsiding at about 1 mm per annum, so when combined with global sea level rise, local sea levels increase.
58
16. What is the overall effect on the UK coastlines due to isostatic adjustment?
The UK is "pivoting": the north is rising (emergent) while the south is sinking (submergent), leading to differing coastal responses.
59
17. Define marine transgression.
Marine transgression is the process where rising sea levels flood low-lying areas, resulting in submergent coastlines.
60
18. What are rias?
Rias are drowned river valleys—V-shaped river valleys that become flooded by the sea, creating estuarine coastlines with sinuous, dendritic plan forms.
61
19. How do rias form?
Rias form when rivers erode steep-sided, V-shaped valleys during glacial periods, which are later inundated by rising sea levels.
62
20. Where are rias commonly found?
They are common in periglacial areas, such as southern England, where glacial erosion carved deep valleys that were later flooded.
63
21. Give an example of a ria.
Kingsbury Estuary on the south Devon coast is an example of a ria, with a main channel near its mouth and drowned tributaries extending inland.
64
22. What are fjords?
Fjords are drowned glacial valleys, typically deeper than the adjacent sea due to intense glacial erosion, and characterized by steep sides and often a shallow entrance.
65
23. How are fjords formed?
Fjords are created by glaciers carving deep U-shaped valleys, which are then flooded when sea levels rise during interglacial periods.
66
24. Where are fjords most commonly found?
Fjords are typical of glaciated regions, such as western Norway and the sea lochs of Scotland.
67
25. What is a key characteristic of a fjord’s entrance?
Many fjords have a shallow entrance due to a submerged terminal moraine or "lip" that was left by retreating glaciers.
68
26. Give an example of a well-known fjord.
Sognefjord in western Norway, which is 205 km long and up to 4.5 km wide in its main branch, is a classic example.
69
27. What are the Dalmatian coasts?
Dalmatian coasts are characterized by long, narrow islands running parallel to the mainland, separated by narrow sea channels called sounds.
70
28. How do Dalmatian coasts form?
They form when sea level rise floods coastal synclines, overtopping low points and isolating anticline ridges as islands.
71
29. Where is the Dalmatian coast located?
The Dalmatian coast is found along the Croatian coastline in the Adriatic Sea, featuring over 1,240 islands along a 520 km stretch.
72
30. What is the significance of isostatic rebound in emergent coastlines?
It exposes relict coastal features and creates raised beaches and fossil cliffs that record past sea levels and marine erosion.
73
31. What does the episodic nature of isostatic rebound cause in coastal morphology?
Periods of little change followed by rapid uplift can allow marine processes to shape the coastline before a sudden drop leaves a relict feature.
74
32. How do emergent coastlines indicate previous sea levels?
They display landforms such as raised beaches and fossil cliffs that were once at sea level but are now elevated due to uplift.
75
33. What is a key difference between emergent and submergent coastlines?
Emergent coastlines expose former sea beds due to land uplift, while submergent coastlines result from rising sea levels that flood terrestrial areas.
76
34. How does marine transgression affect submergent coastlines?
Rising sea levels flood valleys and low-lying areas, transforming river valleys into estuarine or drowned coastlines (rias).
77
35. What type of coastal landform is common along submergent coastlines?
Drowned river valleys (rias) are the most common landforms along submergent coastlines.
78
36. What economic importance do rias hold?
Rias often provide sheltered ports and estuarine environments that are valuable for shipping and harbor activities.
79
37. How are barrier islands on the US east coast formed?
They form from coastal sand dunes that become separated from the mainland by rising sea levels, creating lagoons behind them as the dunes migrate landwards.
80
38. What maintains the separation between barrier islands?
Rivers and tidal flows maintain open water channels between the islands, keeping the barrier system dynamic.
81
39. How does sea level change influence the migration of barrier islands?
As sea levels continue to rise, barrier islands may slowly migrate landwards while their dunes and sediment supply are continuously reshaped by longshore drift.
82
40. How do emergent and submergent processes together shape coastlines?
They create a variety of landforms—from raised beaches and fossil cliffs (emergent) to rias, fjords, and Dalmatian coasts (submergent)—demonstrating the dynamic interplay of isostatic and eustatic forces.
83
41. What role does tectonics play in emergent and submergent coastlines?
Tectonic uplift can enhance emergent coastlines by raising land, while subsidence can accentuate submergence, further modifying coastal features.
84
42. Why is understanding emergent and submergent coastlines important in coastal geography?
It helps in reconstructing past sea level changes, predicting future coastal evolution, and managing coastal resources and hazards effectively.
85
1. What is contemporary sea level change?
It refers to recent changes in sea level caused primarily by global warming and tectonic activity, affecting coastlines today.
86
2. How does climatic warming influence sea level?
Warming leads to eustatic sea level rise by melting mountain glaciers and polar ice sheets, adding water to the oceans, and by thermal expansion of seawater.
87
3. Does melting sea ice affect global sea levels?
No; because sea ice is already floating, its melting does not change the water volume or global sea level.
88
4. What percentage of sea level rise (1990-2010) is attributed to ice sheet melting according to the IPCC?
The IPCC attributes 50% of sea level rise during that period to ice sheet melting (with contributions from the Greenland and Antarctic ice sheets).
89
5. How do the Greenland and Antarctic ice sheets contribute to sea level rise?
Melting of the Greenland ice sheet contributes around 15%, and the Antarctic ice sheet around 10%, to the total sea level rise.
90
6. How does thermal expansion contribute to sea level rise?
As ocean water warms, it expands in volume; the IPCC attributes 40% of the 1990-2010 sea level rise to thermal expansion.
91
7. What fraction of increased heat energy in the climate system is absorbed by the oceans?
Approximately 94% of the increased heat energy is absorbed by the oceans.
92
8. What role does tectonic activity play in contemporary sea level change?
Tectonic processes account for roughly 10% of the observed sea level rise, through mechanisms such as volcanic activity, crustal faulting, and sea floor spreading.
93
9. How does geothermal heat from underwater volcanic activity affect sea level?
It can cause localized thermal expansion of ocean water, contributing to sea level rise.
94
10. How can rising magma at constructive plate boundaries influence sea level?
It domes up the overlying crust, reducing the capacity of the ocean basin and causing a small eustatic sea level rise.
95
11. What effect does tectonic folding at destructive plate margins have on sea level?
Folding can increase the ocean basin volume, potentially lowering sea levels locally.
96
12. How can earthquakes influence sea level?
Earthquakes can uplift or cause rebound of the sea floor; for example, the 2004 Boxing Day tsunami raised sea levels by about 0.1 mm through such processes.
97
13. What is one example of faulting affecting local sea level?
Faulting can uplift crustal blocks, as seen at Turakirae Head near Wellington, NZ, where a 1855 earthquake uplifted the headland by 6 m.
98
14. How does sea floor spreading affect island elevation?
Sea floor spreading can transport volcanic islands away from uplifted zones, causing them to sink as the crust cools and becomes denser.
99
15. What is the overall impact of global warming on contemporary sea level?
Global warming increases sea levels through both ice melt and thermal expansion of the ocean water.
100
16. How much have sea levels risen since 1870?
Observations show that sea levels have risen by approximately 21 cm from 1870 to 2010.
101
17. What has been the acceleration rate of sea level rise since 1940?
Sea level rise has accelerated, reaching about 3 mm per annum between 1990 and 2000.
102
18. What is the predicted range of sea level rise by 2100 according to the IPCC?
The IPCC predicts a sea level rise of between 18-59 cm by 2100 (with some reports suggesting 28-98 cm).
103
19. What does the US National Research Council predict for sea level rise by 2100?
They predict a more extreme range of 56-200 cm by 2100.
104
20. Why is there a wide variation in future sea level predictions?
Uncertainties arise from complex feedback effects, ice melt rates, future greenhouse gas emissions, population and economic growth, and political commitment to mitigation.
105
21. What would be the global impact if the entire Greenland ice sheet melted?
Complete melting of the Greenland ice sheet would raise global sea levels by about 7 m.
106
22. What is the potential impact of complete Antarctic ice sheet melting?
Complete melting could raise sea levels by roughly 50 m, though such an event would take many centuries.
107
23. How do eustatic factors affect sea level?
Eustatic changes are global, driven by changes in the volume of ocean water through ice melt and thermal expansion.
108
24. What are the main eustatic processes causing sea level change?
The two main processes are the melting of glaciers/ice sheets and thermal expansion of seawater.
109
25. What are isostatic changes, and how do they affect sea level?
Isostatic changes involve local vertical movements of the Earth's crust (uplift or subsidence) that alter relative sea level independent of global changes.
110
26. How can human-induced global warming accelerate sea level rise?
Anthropogenic greenhouse gas emissions increase global temperatures, thereby enhancing ice melt and thermal expansion.
111
27. What proportion of sea level rise from 1990-2010 is attributed to thermal expansion?
About 40% is attributed to thermal expansion, according to the IPCC.
112
28. How do tectonic processes contribute to contemporary sea level change?
They influence sea level through processes such as volcanic uplift, crustal faulting, and adjustments in sea floor spreading that modify ocean basin volumes.
113
29. What is an example of tectonic uplift affecting sea level?
Uplift of coastal areas, such as fault-induced uplift, lowers local sea level relative to the land, despite global sea level rise.
114
30. How can crustal subsidence affect sea level?
Subsidence increases relative sea level by causing the land to sink, making coastal flooding more likely.
115
31. What role does the emission of geothermal heat play?
Geothermal heat can warm surrounding water, contributing slightly to thermal expansion and localized sea level rise.
116
32. How does the Boxing Day tsunami illustrate tectonic impact on sea level?
It demonstrated that crustal movement during an earthquake can lift parts of the ocean floor, causing measurable, though small, sea level changes.
117
33. Why is contemporary sea level change a risk to coastlines?
Rising sea levels increase the risk of coastal flooding, erosion, and the eventual submergence of low-lying areas and islands.
118
34. Which types of coastlines are most at risk from sea level rise?
Low-lying coasts, volcanic islands, and coral atolls (e.g., the Maldives, Kiribati) are particularly vulnerable.
119
35. How does sea level rise affect volcanic islands?
They may experience both global warming effects and local tectonic subsidence, increasing the risk of their eventual disappearance.
120
36. What is the significance of contemporary sea level change for coastal management?
Understanding these changes is crucial for planning coastal defenses, managing flood risks, and protecting vulnerable coastal communities and ecosystems.
121
37. How do recent rates of sea level rise compare to past rates?
Past rates were lower; for instance, from 6,000 BP to 1860, the average was about 0.5 mm p.a., compared to the 3 mm p.a. recorded more recently.
122
38. What evidence supports accelerated sea level rise since the 20th century?
Instrumental measurements since 1870 and satellite data since the late 20th century indicate an accelerating trend in sea level rise.
123
39. What role does thermal expansion play in the current climate system?
It is a major contributor, as the vast majority of excess heat is absorbed by the oceans, causing them to expand.
124
40. How does the IPCC quantify the contributions to sea level rise from different sources?
The IPCC provides percentage estimates: around 50% from ice sheet melting, 40% from thermal expansion, and 10% from tectonic activity (for the period 1990-2010).
125
41. Why might future sea level rise be greater than current predictions?
Uncertainties in feedback mechanisms, future emissions, and potential nonlinear responses in ice melt could lead to higher-than-expected rises.
126
42. How should policymakers respond to contemporary sea level change?
They should implement adaptive coastal management strategies, invest in mitigation measures, and plan for long-term risks to vulnerable regions.
127
1. What causes rapid coastal recession in natural systems?
Rapid coastal recession is primarily driven by physical factors where geological and marine characteristics combine to promote erosion.
128
2. What geological factors promote coastal erosion?
Soft lithology (weak, porous, low-cohesion rocks), well-jointed structures, seaward-dipping beds, and heavily faulted rocks all facilitate rapid erosion.
129
3. What marine factors enhance coastal recession?
A long wave fetch, which generates large, destructive waves, and strong longshore drift that swiftly removes collapsed sediment, continuously exposing the coastline.
130
4. How does lithology affect coastal recession?
Softer rock types with weak cohesive bonds are more easily eroded, leading to faster recession compared to harder, more resistant lithologies.
131
5. Why are seaward-dipping beds significant in erosion?
Seaward-dipping beds provide a natural slope that reduces friction and resistance, allowing gravity and wave action to more easily remove material.
132
6. How does a long wave fetch influence erosion?
A long wave fetch allows winds to build up energy over an uninterrupted distance, creating larger and more destructive waves that intensify erosion.
133
7. What role does longshore drift play in coastal recession?
Strong longshore drift removes fallen material quickly, preventing natural beach accumulation, which in turn resets the erosion cycle by exposing fresh rock.
134
8. How can human activity increase rates of coastal recession?
Human activities can interrupt the sediment cell by reducing sediment supply, altering wave dynamics, or directly removing sediment through engineering interventions.
135
9. How do major river dams affect coastal sediment supply?
Dams trap sediment that would normally reach the coast, starving coastal systems of essential sediment and leading to accelerated erosion.
136
10. What example illustrates the impact of dam construction on coastal recession?
The Aswan High Dam on the Nile significantly reduced sediment supply from 130 million tonnes to about 15 million tonnes per year, triggering rapid coastal erosion.
137
11. How did the Aswan High Dam affect the Nile Delta?
The drastic reduction in sediment supply led to an increase in erosion rates from 20-25 m per year to over 200 m per year in the delta region.
138
12. What is dredging in the context of coastal management?
Dredging is the process of removing sediment (sands or gravels) from a beach, river, or estuary, often for maintaining navigable channels or for construction use.
139
13. How can dredging contribute to coastal recession?
By removing sediment that would naturally replenish the coastline, dredging can disrupt the sediment cell and lead to increased erosion.
140
14. What effect does the interruption of sediment supply have on coastal stability?
When sediment supply is interrupted, the natural balance of erosion and deposition is lost, leading to an accelerated retreat of the coastline.
141
15. How do human interventions alter natural coastal processes?
Activities such as dam construction and dredging change sediment dynamics, which can destabilize coastlines by preventing natural sediment replenishment.
142
16. Which coastal areas are particularly at risk from these human activities?
Low-lying deltas and coastal zones—such as the Nile Delta, certain sections of the Guinea and Californian coastlines—are especially vulnerable to increased erosion.
143
17. What is the role of coastal management in addressing these issues?
Coastal management aims to mitigate erosion by balancing human activities with natural sediment supply and by implementing measures to protect and replenish the coastline.
144
18. Why is sediment supply critical for coastal stability?
Adequate sediment supply helps maintain beach profiles and protects cliffs from undercutting, acting as a buffer against natural and human-induced erosion.
145
19. How can coastal management reduce the risk of accelerated coastal recession?
By regulating activities like dam construction and dredging, and by implementing sediment nourishment projects, coastal management can help restore natural sediment flow.
146
20. What is the broader significance of human impacts on coastal recession?
Human actions can significantly alter natural coastal systems, potentially leading to loss of land, increased flood risk, and long-term environmental and economic consequences.
147
1. How do weathering and mass movement interact in coastal recession?
Weathering weakens rock by reducing internal cohesion, making it more susceptible to mass movement; repeated slumping accelerates coastal recession.
148
2. What role does weathering play above the high tide mark?
Weathering weakens the rock above the high tide mark, facilitating mass movement (e.g., blockfalls or slumping) that leads to rapid cliff retreat.
149
3. How does weakened rock between high and low tide marks affect marine erosion?
Weakened rock in this zone erodes faster under wave attack, increasing the rate of marine erosion and contributing to quicker coastal recession.
150
4. What happens when a wave-cut notch forms in weathered rock?
A wave-cut notch in weakened rock can trigger rapid cliff collapse through mass movement, thus accelerating coastal recession.
151
5. How do repeated mass movement events influence coastal recession?
Each mass movement event removes a portion of the cliff, and repeated events cumulatively cause rapid coastal retreat.
152
6. What is the significance of small-scale fluvial erosion on coastal slopes?
Rainwater forms rills and gullies, especially in unconsolidated material, which further weakens slopes and contributes to overall coastal recession.
153
7. How do hard engineering defences at Overstrand affect the coastal system?
At Overstrand, coastal defences protect the cliff foot from marine erosion, yet hydration weathering and repeated slumping above continue to drive rapid coastal recession.
154
8. Why might hard engineering solutions be insufficient to halt coastal recession completely?
Although they reduce direct marine erosion at the base, they do not stop subaerial processes (like weathering and mass movement) that continue to weaken and destabilize the cliff.
155
9. In what way does hydration weathering contribute to cliff retreat?
Hydration weathering occurs when water is absorbed by minerals in the rock, expanding them and further weakening the rock structure, thus promoting slumping.
156
10. What is the overall effect of subaerial processes on coastal landforms?
They modify coastal morphology by accelerating cliff recession, creating features such as wave-cut notches, scarps, and terraced profiles as the land retreats.
157
1. What are temporal variations in coastal recession?
They are changes in the rate of coastal recession over time, influenced by short- and long-term factors such as wind, tides, storms, seasons, and weather systems.
158
2. How does wind direction affect coastal recession?
Onshore winds increase wave energy and erosion rates, while offshore winds produce calm conditions that slow erosion.
159
3. What is the difference between dominant and prevailing winds?
Dominant wind is the direction of the strongest winds, while prevailing wind is the most common wind direction.
160
4. How does wind direction from the prevailing or dominant wind contribute to erosion?
When wind blows from these directions, large destructive waves are generated, rapidly eroding the coastline.
161
5. What is fetch, and why is it important?
Fetch is the uninterrupted distance over open water where the wind blows; a longer fetch allows for greater wave energy development, enhancing erosion.
162
6. How can moderate winds over a long fetch produce rapid recession?
Even moderate winds can generate large, destructive waves if they have a long fetch to build energy, leading to rapid coastal erosion.
163
7. Provide an example of fetch influencing erosion rates.
In North Norfolk, a dominant north wind with a 1,600 km fetch across the Norwegian and North Seas can cause recession rates of up to 8 m per annum.
164
8. How do tides influence coastal recession?
High tide increases water depth on the foreshore, allowing waves to reach the backshore with more energy, which increases erosion and recession.
165
9. When do high tides occur?
High tides occur twice daily, approximately 12 hours apart.
166
10. What are Spring Tides, and why are they significant?
Spring Tides occur twice each lunar month when the Sun and Moon align, creating exceptionally high tides that boost erosion rates.
167
11. What does the IPCC estimate regarding sea level rise and erosion?
The IPCC estimates that a 1 cm rise in sea level results in an average of 1 m of horizontal erosion.
168
12. How does global warming affect sea level and coastal recession?
Global warming causes thermal expansion of water and ice melt, leading to higher sea levels, which in turn enhance wave energy at the coast and accelerate erosion.
169
13. How do storm events influence coastal recession?
Storms, characterized by deep low-pressure systems, produce large, high-energy waves that significantly increase erosion and recession rates.
170
14. What defines a storm event in terms of coastal erosion?
Storms are deep depressions with very low pressure that generate destructive waves capable of rapid coastal retreat.
171
15. How is global warming predicted to affect storm activity?
It is expected to increase both the frequency and intensity of storm events, thereby accelerating coastal recession.
172
16. During which season are storms more frequent and intense in the UK?
Storm events are more common and intense in winter due to greater contrasts between tropical and polar air masses.
173
17. How do seasonal variations affect coastal recession rates?
In winter, stronger winds, higher tides, and more frequent storms result in faster coastal recession than in summer.
174
18. What is the typical range of erosion in Holderness during winter storms?
Erosion can range from 2 to 6 m per event in winter, with annual averages varying from 0 to 6 m (approximately 1.25 m on average).
175
19. How do phenomena like El Niño affect storm intensity in the UK?
During El Niño events, which occur every 2–7 years, storms may be weaker, potentially reducing erosion rates temporarily.
176
20. How does the 11-year solar cycle influence coastal erosion?
Phases of low solar output in the cycle can lead to reduced storm intensity, thus lowering erosion rates during those periods.
177
21. How do weather systems affect coastal recession?
The UK lies at the polar front, where the interaction of warm and cold air produces both anticyclones (gentle winds) and depressions (strong winds), impacting erosion rates.
178
22. What is the effect of anticyclones on coastal recession?
Anticyclones produce calm conditions with gentle winds and small waves, leading to lower erosion rates.
179
23. What impact do depressions have on the coast?
Depressions generate strong winds and high-energy waves that cause rapid coastal erosion.
180
24. How do depressions travel across the UK?
They form in the North Atlantic and move across the UK from southwest to northeast, with spiraling inflow air causing changes in wind direction.
181
25. How does a change in wind direction during a weather system affect erosion?
Shifting wind directions can create alternating periods of high-energy and calm conditions, resulting in fluctuating rates of coastal erosion.
182
26. What role does fetch play during high-energy wind conditions?
A long fetch allows winds to build substantial energy, resulting in larger, more destructive waves that increase coastal recession.
183
27. How do onshore winds combined with high tides affect the backshore?
They allow waves to reach the backshore with high energy, which increases the impact of erosion and accelerates coastal recession.
184
28. How does the increased water depth during high tide affect wave energy?
Deeper water in the foreshore at high tide permits waves to maintain their energy until reaching the backshore, enhancing erosion.
185
29. What is the relationship between sea level rise and coastal recession?
A rise in sea level leads to deeper water at the coast, allowing waves to erode the backshore more effectively, thereby increasing recession rates.
186
30. How does global warming contribute to the frequency of high-energy events at the coast?
By increasing sea levels and the intensity of storms, global warming creates conditions that favor more frequent and powerful coastal erosion events.
187
31. How do local geographical features modify the effects of wind and tides?
Features such as headlands, bays, and inlets can alter fetch and wave direction, leading to spatial variations in erosion rates along the coast.
188
32. How does the duration of a storm affect coastal recession?
Longer-lasting storms can cause more prolonged exposure to high-energy waves, resulting in greater overall erosion.
189
33. What is the overall effect of fluctuating wind directions on coastal erosion?
They cause variable erosion rates as alternating periods of high-energy (onshore, strong fetch) and low-energy (offshore, calm) conditions occur.
190
34. How do short-term weather variations combine with longer-term trends in coastal recession?
Short-term events like storms and high tides overlay longer-term trends from climate change and sea level rise, making coastal erosion highly dynamic.
191
35. How do temporal variations affect coastal management strategies?
Managers must consider both immediate storm impacts and long-term climate trends to develop adaptive strategies that protect vulnerable coastlines.
192
36. What challenges do temporal variations present to predicting coastal recession?
The variability in wind, tide, and storm conditions creates complex and sometimes unpredictable erosion patterns, complicating long-term planning.
193
37. How does the synergy of wind, tides, and storms contribute to rapid coastal recession?
When all these factors align—onshore winds with long fetch, high tides, and storm events—the resulting high-energy waves can cause very rapid erosion.
194
38. What specific example illustrates extreme temporal variation in coastal recession?
In North Norfolk, a dominant north wind with a 1,600 km fetch can produce recession rates up to 8 m per annum under favorable conditions.
195
39. How does the timing of high tide during a storm influence erosion?
When high tide coincides with a storm, deeper water allows for maximum wave energy to impact the coast, accelerating erosion.
196
40. What is the significance of the IPCC estimate linking sea level rise to horizontal erosion?
It quantifies the impact of sea level rise—every 1 cm increase can cause an additional 1 m of horizontal erosion, highlighting the sensitivity of coastlines.
197
41. How might future climate change alter temporal variations in coastal recession?
Increased sea levels, more frequent and intense storms, and shifting wind patterns due to global warming are likely to accelerate coastal recession further.
198
42. Summarise how wind direction, tides, storms, seasons, and weather systems collectively influence coastal recession.
They interact dynamically—onshore winds with long fetch and high tides, especially during winter storms and depressions, generate high-energy waves that rapidly erode the coast, while calmer conditions temporarily reduce erosion, creating a highly variable temporal pattern.
199
1. Why are many low-lying coastal areas densely populated?
Because beaches and the sea attract tourism, coastal deltas are fertile for agriculture, and estuaries offer excellent navigable access for trade.
200
2. What types of urban centers are commonly found in river deltas?
Megacities such as Shanghai (Yangtze Delta), Dhaka (Ganges-Brahmaputra Delta), and Karachi (Indus Delta) are common.
201
3. What percentage of the world's population is predicted to live in coastal regions less than 10 m above sea level by 2060?
The IPCC predicts about 12% of the world's population will live in these low-lying coastal areas.
202
4. How does low topographic height increase flood risk?
Low-lying areas (1-2 m above high tide) are easily overtopped by storm surges and even by gradual global sea level rise, leading to temporary or permanent flooding.
203
5. Provide an example of a low-lying archipelago at risk.
The Maldives, where the highest point is only 2.3 m above sea level and Malé is protected by a 3 m sea wall, is extremely vulnerable.
204
6. How does coastal height affect flood risk?
Areas with minimal elevation offer little buffer against rising seas and storm surges, increasing the likelihood of inundation.
205
7. What is subsidence?
Subsidence is the gradual sinking or lowering of land due to natural or human-induced factors, which increases the relative sea level locally.
206
8. What natural process causes subsidence in deltas and estuaries?
The settling and compaction of recently deposited sediment can naturally cause subsidence.
207
9. How can human activities contribute to subsidence?
Activities like groundwater abstraction, drainage of saturated soils, and the weight of urban development compress sediment, causing additional subsidence.
208
10. Give an example of human-induced subsidence.
In the Fens of East Anglia and in Venice, ground water abstraction and the weight of buildings have led to significant subsidence.
209
11. How does periodic isostatic subsidence affect deltas?
When delta sediments reach a threshold weight, the crust depresses, leading to marine transgression and increased flood risk.
210
12. What example illustrates subsidence in the Ganges-Brahmaputra delta?
Since 1960, 50 large islands in the delta have subsided by about 1.5 m due to a combination of isostatic depression, water abstraction, and natural sediment settling.
211
13. How does vegetation removal increase coastal flood risk?
Vegetation such as salt marshes and mangroves stabilizes sediment, traps new deposits, and absorbs wave energy; their removal weakens these protective functions.
212
14. What is the impact of mangrove forests on wave energy?
A 100 m belt of mangrove forest can reduce wave height by around 40%, while a 1 km belt can lower a storm surge by about 0.5 m.
213
15. How much of the world's mangrove forest has been lost since 1950?
Approximately 50% of the world's mangrove forest has been removed, with major losses due to shrimp farming and coastal development.
214
16. What are the implications of vegetation loss in Bangladesh's Sundarbans?
With 71% of the 180 km Sundarbans experiencing vegetation removal, parts of the delta are eroding at rates of up to 200 m per annum, increasing flood risk.
215
17. How does global sea level rise exacerbate local flood risk?
Rising sea levels increase the frequency and extent of coastal flooding, particularly in low-lying areas, by reducing the natural buffer between land and sea.
216
18. What was the mean global sea level rise during the 20th century?
Global sea level rose by approximately 20 cm over the 1900s.
217
19. How do coastal defences interact with sea level rise?
While defences like sea walls protect low-lying areas (e.g., 50% of the Netherlands, East Anglian Fens), they may be overwhelmed as sea levels continue to rise.
218
20. What sea level rise does the IPCC predict by 2100?
The IPCC predicts a further sea level rise of 18–59 cm by 2100.
219
21. How might a 40 cm sea level rise affect Bangladesh?
A 40 cm rise could permanently submerge about 11% of Bangladesh, potentially displacing 7–10 million people as environmental refugees.
220
22. What is the potential impact of a 50 cm sea level rise on the Maldives?
A 50 cm rise would permanently flood around 77% of the Maldives' land area.
221
23. Why do low-lying deltas attract high population densities?
Their fertile soils support agriculture and the navigable waterways facilitate trade, attracting dense settlements and megacities.
222
24. How does urbanization contribute to coastal flood risk?
The weight of cities compresses underlying sediments and, combined with water abstraction, can accelerate subsidence, increasing flood risk.
223
25. What role do estuaries play in coastal economies?
Estuaries are ideal for trade due to navigable rivers and often support significant population centers and industries.
224
26. How does global sea level rise interact with local subsidence to affect flood risk?
Both global sea level rise and local subsidence lower the relative elevation of the coast, compounding flood risks in vulnerable regions.
225
27. What is the significance of the IPCC's prediction regarding coastal populations?
It highlights that a significant proportion of the global population is at risk, emphasizing the need for adaptive coastal management strategies.
226
28. How does sediment deposition normally counteract subsidence?
Fresh sediment and bioaccretion from organic matter can build up land, countering natural subsidence in some coastal areas.
227
29. What happens when sediment deposition is prevented by human activity?
When sediment supply is interrupted (e.g., by dams), natural replenishment is reduced, and subsidence may dominate, increasing flood risk.
228
30. How has the construction of the Aswan High Dam influenced coastal erosion and flood risk?
It has dramatically reduced the sediment supply to the Nile Delta, increasing erosion rates and the risk of flooding due to reduced natural sediment replenishment.
229
31. How do river deltas contribute to coastal flood risk?
Deltas are low-lying and subject to both natural subsidence and sea level rise, making them particularly vulnerable to flooding.
230
32. What is the effect of vegetation on sediment stability?
Vegetation binds sediment together and traps additional deposits, effectively raising land elevation and reducing flood risk.
231
33. How does the removal of coastal vegetation affect wave energy?
Without vegetation, more wave energy reaches the shore, leading to increased erosion and higher flood risk.
232
34. What are the main factors that determine local flood risk on coastlines?
Key factors include the elevation of the land (height), rate of subsidence, degree of vegetation cover, and the extent of global sea level rise.
233
35. How do storm surges interact with low-lying coastlines?
Storm surges can temporarily raise sea levels dramatically, inundating low-lying areas that are only 1-2 m above current sea level.
234
36. Why are coastal regions attractive despite their flood risks?
They offer economic opportunities, fertile agricultural land, and strategic advantages for trade and tourism, which often outweigh the risks for many populations.
235
37. What challenges do megacities in deltas face in terms of flood risk?
They are particularly at risk due to high population density, extensive urbanization, and the combined effects of sea level rise and subsidence.
236
38. How does groundwater abstraction contribute to coastal flood risk?
It reduces the water content in sediments, leading to compaction and subsidence, which in turn lowers the ground level relative to the sea.
237
39. What is the consequence of coastal defences failing under rising sea levels?
Failure of coastal defences can lead to widespread flooding, loss of property, and displacement of populations in vulnerable regions.
238
40. How can sustainable coastal management help mitigate flood risk?
By restoring natural sediment processes, protecting and replanting vegetation, and carefully planning urban and agricultural water use to reduce subsidence.
239
41. What global trend exacerbates local coastal flood risks?
Ongoing global sea level rise, driven by climate change, amplifies the vulnerability of low-lying coastal regions.
240
42. Summarise the main local factors that increase coastal flood risk.
Low land height, subsidence (natural and human-induced), and vegetation removal all increase flood risk, which is further exacerbated by global sea level rise.
241
1. What is a storm surge?
A storm surge is a temporary rise in local sea level produced when a depression, storm, or tropical cyclone reaches the coast.
242
2. What causes a storm surge?
Low air pressure and strong onshore winds during depressions or tropical cyclones cause the ocean surface to dome upward, creating a storm surge.
243
3. How does air pressure affect sea level during a storm?
A reduction of 1 millibar in air pressure typically causes a 1 cm rise in sea level.
244
4. What are depressions in meteorological terms?
Depressions are areas of low surface air pressure generating winds that spiral anti-clockwise (in the Northern Hemisphere) into the centre.
245
5. Where are depressions common?
They are common in mid-latitude regions such as the UK.
246
6. What distinguishes tropical cyclones from depressions?
Tropical cyclones are deeper, more intense low-pressure systems with wind speeds of 118 km/h or more, classified on the Saffir-Simpson scale.
247
7. How are tropical cyclones classified?
They are classified into 5 categories on the Saffir-Simpson scale, with Category 5 having winds over 250 km/h.
248
8. How does high air pressure influence the ocean surface?
High air pressure depresses the ocean surface, lowering local sea level.
249
9. What is the effect of low air pressure on the ocean?
Low air pressure allows the ocean surface to dome upward, raising local sea level.
250
10. Quantitatively, what is the relationship between air pressure drop and sea level rise?
A 1 millibar drop in air pressure is associated with approximately a 1 cm rise in sea level.
251
11. When are storm surges most accentuated?
They are accentuated at high tide (especially during spring tides), where the coastline funnels and the sea bed shallows near the coast.
252
12. How does a funnel-shaped coastline affect storm surges?
A funnel shape concentrates water, increasing surge height and energy, thus intensifying coastal flooding.
253
13. What additional factor intensifies storm surge impacts?
Large, destructive waves generated by strong storm winds enhance the surge's erosion potential.
254
14. What immediate human impacts can result from storm surges?
Storm surges can cause deaths, injuries, building collapses, and immediate infrastructure damage.
255
15. What are some longer-term social impacts of storm surges?
They can lead to hypothermia, waterborne diseases, disrupted transport, and prolonged economic losses due to damaged infrastructure.
256
16. Which infrastructure is vulnerable to storm surges?
Roads, railways, ports, airports, water pipes, electricity lines, sewage systems, and housing are particularly vulnerable.
257
17. How do storm surges impact vulnerable housing?
Poorly built or low-cost homes on marginal low-lying land (e.g., slums, shantytowns) are most susceptible to damage and prolonged recovery.
258
18. What economic sectors are affected by storm surges?
Business operations, industrial facilities, and agriculture (through contaminated land and lost crop harvests) can be severely impacted.
259
19. What were the key characteristics of Tropical Cyclone Sidr (2007) in Bangladesh?
Cyclone Sidr was a Category 4 system with a central pressure of 944 mb, wind speeds of 240 km/h, and produced a 6 m storm surge.
260
20. How did geographical features worsen Cyclone Sidr's impact in Bangladesh?
The funnel shape of the Bay of Bengal and the outflow from the Ganges and Brahmaputra rivers focused surge waters onto Bangladesh.
261
21. How did intense rainfall contribute to Cyclone Sidr's effects?
Intense rainfall increased flooding, compounding the surge impact and exacerbating coastal inundation.
262
22. How did local geology affect Cyclone Sidr's damage?
The unconsolidated delta sediments and deforestation of protective mangrove swamps increased the region's susceptibility to erosion and flooding.
263
23. What were the human impacts of Cyclone Sidr in Bangladesh?
Approximately 15,000 deaths, 55,000 injuries, destruction of 1.6 million homes, and extensive damage to roads, electricity lines, and agricultural land.
264
24. What was the estimated economic loss from Cyclone Sidr?
The economic loss was estimated at around $1.7 billion.
265
25. How have improvements reduced storm surge impacts in Bangladesh?
Enhanced warnings, embankments, and cyclone shelter networks have lowered death tolls compared to past events like the 1970 Bhola Cyclone.
266
26. What were the key features of Storm Xavier (December 2013) in the UK?
Storm Xavier had winds over 80 mph, coincided with spring tide, and generated significant storm surges along the North Sea coast.
267
27. How did the North Sea funnel contribute to Storm Xavier's impact?
The narrowing of the coastline in the North Sea acted as a funnel, concentrating the surge and increasing local water levels.
268
28. What were the recorded surge heights during Storm Xavier?
Average surges of 3 m were recorded in East Anglia, with surges up to 6 m at Blakeney in North Norfolk.
269
29. What were the human impacts of Storm Xavier in the UK?
Two people were killed, 18,000 were evacuated, coastal defenses were breached in Yorkshire and Kent, and 1,400 homes were flooded.
270
30. What infrastructure damage occurred in Hemsby, Norfolk, during Storm Xavier?
Erosion of sand dunes destroyed seven houses and a lifeboat station, and rail services were suspended for one day.
271
31. What was the estimated economic loss from Storm Xavier?
The total economic loss was estimated at around $100 million.
272
32. How did Storm Xavier's impacts compare to the 1953 storm surge?
Storm Xavier caused significantly less damage and fewer deaths than the 1953 surge, which killed 307 people and flooded 65,000 ha of farmland.
273
33. What measures helped mitigate Storm Xavier's impact?
Improved flood defenses (such as the Thames Barrier), better forecasting, and efficient evacuations helped reduce casualties and economic losses.
274
34. How do coastal defenses reduce the impact of storm surges?
They protect vulnerable areas by limiting inundation, absorbing wave energy, and preventing rapid coastal erosion.
275
35. What is the Saffir-Simpson scale used for?
It classifies tropical cyclones based on wind speed, ranging from Category 1 (least intense) to Category 5 (most intense).
276
36. How do tropical cyclones differ from mid-latitude depressions?
Tropical cyclones are more intense, with lower pressures and higher wind speeds, whereas mid-latitude depressions typically have lower wind speeds and moderate surges.
277
37. How does the funneling of a coastline enhance storm surge effects?
Funneling concentrates incoming water into a narrower area, increasing surge height and energy, which leads to more severe flooding.
278
38. In what way can storm surges accelerate coastal erosion?
The onshore current force of the surge, combined with high-energy waves, can erode coastal sediments and breach defenses rapidly.
279
39. How does the timing of high tide during a storm influence surge severity?
If a storm surge coincides with high tide—especially during a spring tide—the surge's impact is greatly amplified due to deeper water allowing more energy to reach the coast.
280
40. What is the combined effect of low air pressure and strong winds on the ocean surface?
They cause the ocean surface to dome upward, resulting in a higher local sea level that increases the likelihood of flooding.
281
41. What are the long-term social consequences of repeated storm surge events?
Repeated events can lead to loss of life, displacement of communities, prolonged economic disruption, and degradation of critical infrastructure.
282
42. Summarise the key differences in storm surge characteristics between mid-latitude storms and tropical cyclones.
Mid-latitude storms (depressions) typically produce wind speeds around 90 km/h with moderate surges, while tropical cyclones generate much higher wind speeds (≥118 km/h) and more severe surges, as classified by the Saffir-Simpson scale.
283
1. How does climate change affect coastal flood risk?
It increases flood risk by intensifying storms and raising global sea levels, which together lead to more frequent and severe coastal flooding.
284
2. What does the IPCC 5th Assessment Report (2014) predict for sea level rise by 2100?
It predicts that sea level will rise by between 18–59 cm by 2100, with high confidence.
285
3. What factors contribute to uncertainty in sea level rise predictions?
Uncertainties arise from future population growth, economic development, natural positive and negative feedbacks, and political commitment to restrict GHG emissions.
286
4. How does climatic warming contribute to sea level rise?
Warming increases sea level by melting mountain glaciers and polar ice sheets, adding water to the oceans, and by causing thermal expansion of ocean water.
287
5. Why doesn't melting sea ice affect sea level?
Because sea ice is already floating, it displaces its own volume of water; its melting does not alter the overall sea level.
288
6. What percentages of sea level rise (1990–2010) are attributed to ice melt and thermal expansion, according to the IPCC?
About 50% is attributed to melting ice sheets (with Greenland 15% and Antarctic 10%), and around 40% to thermal expansion.
289
7. What role does tectonic activity play in sea level rise?
Tectonic activity contributes roughly 10% through processes such as underwater volcanic activity, magma uplift, and crustal faulting.
290
8. How can global warming influence tropical cyclone characteristics?
Warmer ocean temperatures and a moist atmosphere are predicted to increase cyclone intensity by 2–11% and raise associated rainfall by about 20%, though frequency may remain unchanged.
291
9. What does low confidence mean regarding tropical cyclone predictions?
It indicates that while some models suggest increased intensity, the evidence is variable and no statistically significant long-term trend in maximum intensity has been observed globally.
292
10. How do storm surges form in relation to atmospheric pressure?
Low air pressure allows the ocean surface to dome upward; a 1 millibar drop in pressure can cause about a 1 cm rise in sea level, contributing to storm surge.
293
11. How does a tropical cyclone differ from a mid-latitude depression in terms of storm surges?
Tropical cyclones are deeper low-pressure systems with much higher wind speeds (≥118 km/h) and produce more severe surges, while mid-latitude depressions have moderate winds and surges.
294
12. What scale is used to classify tropical cyclones?
The Saffir-Simpson scale, which ranges from Category 1 to Category 5 based on wind speed.
295
13. What adaptation measures can mitigate coastal flood risk?
Measures include building sea walls, constructing storm surge barriers, creating artificial islands, erecting earth embankments, and restoring mangrove forests.
296
14. Give an example of a sea wall used for coastal protection.
Malé, the capital of the Maldives, is protected by a 3 m sea wall.
297
15. What is Hulhamalé and why is it significant?
Hulhamalé is an artificial island built from reclaimed seabed sediment between 1997 and 2002, standing 4 m above sea level at a cost of $32 million, serving as a coastal adaptation measure.
298
16. How do storm surge barriers protect coastlines?
They control water flow and prevent high surge water from inundating coastal areas; examples include the Thames Barrier and the Eastern Scheldt Barrier in the Netherlands.
299
17. How do mangrove forests reduce coastal flood risk?
Mangroves act as natural protection belts by absorbing wave energy, reducing wave height, and trapping sediment; for example, a 100 m mangrove belt can reduce wave height by about 40%.
300
18. What role does adaptation play in influencing coastal flood risk?
Adaptation measures, such as engineering defences and ecosystem restoration, can mitigate the impact of sea level rise and storms, although they may not completely offset risks.
301
19. How can global warming affect the frequency and magnitude of storms?
It is predicted to increase the intensity of atmospheric circulation, leading to more frequent and stronger storm events, which exacerbate coastal flooding.
302
20. What is the potential impact of a 40 cm sea level rise on Bangladesh?
A 40 cm rise could permanently submerge about 11% of Bangladesh, potentially creating 7–10 million environmental refugees.
303
21. How might a 50 cm sea level rise impact the Maldives?
It could permanently flood approximately 77% of the Maldives' land area, putting the entire archipelago at risk.
304
22. What is the significance of positive and negative feedback in this context?
They are natural processes that can amplify (positive) or mitigate (negative) the effects of warming, contributing to uncertainties in sea level rise predictions.
305
23. How might future policy decisions affect sea level rise?
Stricter policies on greenhouse gas emissions and better adaptation measures could mitigate the extent of future sea level rise, while inaction could lead to higher impacts.
306
24. How does thermal expansion work in the context of sea level rise?
As ocean water warms, it expands, increasing its volume; since about 94% of excess heat is absorbed by the oceans, thermal expansion is a major contributor to sea level rise.
307
25. Why is there high confidence in the projected sea level rise of 18–59 cm by 2100?
Because extensive data and climate models consistently support this range, despite uncertainties in the pace and precise magnitude due to complex feedbacks.
308
26. What does the term "eustatic" refer to in sea level change?
Eustatic changes are global changes in sea level resulting from variations in the volume of water in the oceans due to ice melt and thermal expansion.
309
27. What does "isostatic" change refer to?
Isostatic changes are local variations in sea level caused by vertical movements of the Earth's crust, such as uplift or subsidence.
310
28. How do anthropogenic (human-induced) factors influence sea level rise?
Through greenhouse gas emissions that drive global warming, anthropogenic factors accelerate both ice melt and thermal expansion, thereby increasing sea levels.
311
29. How do increased storm intensities affect coastal flood risk?
More intense storms lower surface air pressure further, producing larger storm surges and causing more severe coastal flooding.
312
30. What is the expected impact of intensified depressions on coastal flooding?
Intensified depressions, with their stronger winds and lower pressures, are likely to generate more frequent and higher storm surges, raising flood risks along mid-latitude coastlines.
313
31. How might polar front jet streams contribute to coastal flood risk?
Accelerated polar front jet streams may increase the number and intensity of depressions, which in turn produce more frequent storm surges in mid-latitude regions.
314
32. How does the variability in tropical cyclone data affect predictions?
The high variability in tropical cyclone intensity and frequency leads to low confidence in predicting long-term trends, despite some observed increases in North Atlantic storm activity.
315
33. What has been observed about tropical cyclone frequency in the North Atlantic?
The number of tropical storms becoming hurricanes has risen from an average of 6 per year in the 1900s to about 8 per year from 2000–2016, although this trend has low confidence.
316
34. What is the role of enhanced atmospheric moisture in cyclone intensity?
A warmer atmosphere can hold more moisture, which may fuel stronger tropical cyclones with higher rainfall, even if the number of cyclones does not increase significantly.
317
35. How do feedback mechanisms contribute to uncertainty in sea level predictions?
Feedbacks (both positive and negative) involving ice melt, ocean heat uptake, and cloud cover can either amplify or moderate warming effects, making precise predictions challenging.
318
36. What are some key uncertainties in projecting future coastal flood risk?
Uncertainties include the rate of future greenhouse gas emissions, the response of ice sheets, economic and population growth, and the effectiveness of future adaptation measures.
319
37. How does improved forecasting and early warning affect storm surge outcomes?
They enable timely evacuations and preparations, reducing casualties and damage despite the severity of storm surge events.
320
38. What is one of the main adaptation strategies for low-lying coastal areas?
Building coastal defences such as sea walls, storm surge barriers, and restoring natural buffers like mangrove forests.
321
39. How does the cost of adaptation factor into coastal flood risk management?
High adaptation costs can limit implementation, leaving vulnerable regions at greater risk if funds and political will are lacking.
322
40. What is the potential global impact if current trends continue?
Continued sea level rise and increased storm intensity could expose millions to flooding, especially in densely populated low-lying coastal regions.
323
41. How can coastal flood risk be mitigated beyond structural measures?
By reducing greenhouse gas emissions through mitigation efforts, thereby limiting future global warming and associated sea level rise.
324
42. Summarise the impact of climate change on coastal flood risk.
Climate change is expected to increase coastal flood risk by raising sea levels (through ice melt and thermal expansion) and intensifying storms (leading to higher storm surges). Although there is high confidence in a 18–59 cm sea level rise by 2100, uncertainties remain due to feedback effects, future emissions, and adaptation efforts, making the exact pace and magnitude of risk difficult to predict.
