OA SEA LEVEL RISE

Question 1

what is the definition of mean sea level? what sort of information is filtered out?

Answer 1

the average height of the sea over longer periods of time (usually a month or year)
- short term variations in waves, tides and storm surges are filtered out

Question 2

what happens to mean sea level between glacial and inter glacial periods? what happened to it during the last interglacial (125,000 years ago) and during the last ice age?

Answer 2

• fluctuations in sea level
• sea level 5m above that of today in the last interglacial
• sea level fell to >100m below today during the last ice age due to water trapped in the ice sheets

Question 3

how has the rate of MSLR increased during the late 19th and early 20th centuries compared to from 1993-2021?

Answer 3

• increases by ~1.7 mm/yr in late 19th and early 20th centuries
• increases by ~3.3mm/yr from 1993-2021

Question 4

what sorts of coastal zones are the highest risk/most vulnerable to changes in MSL? what is the % of people that live within 100km of coast ?

Answer 4

• dense populations
• low elevations (need dykes and dams to keep sea out)
• appreciable rates of subsidence (small island nations)
• and/or inadequate adaptive capacity
• about 40% of population live within 100km of the coast

Question 5

what sorts of coastal zones are the highest risk/most vulnerable to changes in MSL? what is the % of people that live within 100km of coast ?

Answer 5

• dense populations
• low elevations (need dykes and dams to keep sea out)
• appreciable rates of subsidence (small island nations)
• and/or inadequate adaptive capacity
• about 40% of population live within 100km of the coast

Question 6

what is the nature of the spread of rate of sea level rise across the globe? what can natural variability be caused by?

Answer 6

• rate of rise is not uniform, particularly varying around the southern pacific and indian ocean
• natural variability caused by ENSO & ocean currents

Question 7

what are the major contributors to mean sea level rise?

Answer 7

• thermal expansion (warmer water expands and takes up more space)
• glaciers
• ice sheets (greenland and antarctica)

Question 8

what are the natural seasonal processes which cause the melting of glaciers and polar ice caps? therefore, what are rising temperatures caused by?

Answer 8

• in summer, glaciers and polar ice caps naturally melt back
• in winter, the snow balances out the melting
• rising temps are caused by a) greater than average summer melting, and b) reduced snowfall
• seeing these patterns due to winter starting later and spring starting earlier
• imbalance results in strong net gain of runoff vs evaporation for the ocean, causing SLR

Question 9

what are the effects of inundation, flood and storm damage, which are impacts of MSLR? what are the causes impacts of over-wash, with Kwajalein Atoll as an example?

Answer 9

• modifies propagation of tides and storm surges, raises risks of extreme events
• greater wave heights -> greater wave-driven run-up -> raised groundwater levels -> salinised freshwater lens -> making it basically undrinkable for the island

Question 10

wetland migration and “coastal squeeze”: what occurs when there is no seawall present, seawall present, and naturally rising land?

Answer 10

1. saltmarsh can migrate landward. under normal conditions, as conditions change slowly, saltmarshes migrate inward, and there is erosion of the seaward edge
2. landward migration prevented. get habitat squeeze bc the seawall prevents migration- the saltmarsh will become flooded and disappear. behind these seawalls is reclaimed land generally used for grazing/agriculture
3. landward migration prevented. naturally rising land prevents migration, and this can also cause coastal squeeze.

Question 11

what does saltwater intrusion (another impact of MSLR) have implications for? why is this? what is there an eventual collapse in?

Answer 11

• freshwater aquifers/lenses
• intrusion of saltwater causes seagrass dieback and mangrove expansion. freshwater peat soil begins to degrade with exposure to saltwater.
• peat collapse; freshwater peat collapses and the water is too deep for plants to become established. mangroves established elsewhere help to re-stabilise soil.

Question 12

what is marine inundation?

Answer 12

flooding by ground seawater

Question 13

SUMMARY:
large variations in sea level in the g… past
- recent changes driven by … …
main contributors to SLR: thermal …, glacial … and the … of the Polar … …
main impacts of MSLR: coastal i…, f…, wetland m… or l…, coastal …, saltwater int… and rising g… water tables
adaptive m… strategies for urban areas need to take into consideration both m… in… and gr… int… into their adaptive.

Answer 13

geological
climate change
expansion
melt
melting
ice sheets
inundation
flooding
migration
loss
erosion
intrusion
ground
management
marine inundation
groundwater intrusion