OA lecture 5 - Jasmine Flashcards
define mean sealevel (MSL)
Mean sea level: is the average height of the sea over longer periods of time (usually a month or year)
what is filtered out in sea level change
Short-term variations in waves, tides & storm surges are filtered out
how much higher was the last interglacial
Last interglacial (125,000 years ago) sea level 5 m above that of today
when the sea level fells, where was water trapped? how far did the sea level fall?
The sea level fell to >100 m below today; water was trapped in ice sheets during the last ice age.
has the sea level changed much in the past 2000 years?
no- very little
recent changes in MSL how much- during late 19th and early 20th centuries
1.7mm/yr-1
recent changes in MSL how much- 20th century
1.7mm/yr-1
recent changes in MSL how much- 1993-2021
3.3mm/yr-1
identify vulnerable regions to mean sea level rise
Highest risk to changes in MSL are coastal zones with
dense populations
low elevations
appreciable rates of subsidence
and/or inadequate adaptive capacity
Rate of rise is not….
uniform
natural variability in SLR due to…
ENSO
ocean current
3 major contributors to MSL
Thermal expansion;
Glaciers;
Ice sheets (Greenland and Antarctica).
what is the natural process of Melting of glaciers and polar ice caps
Summer: Naturally melt back
Winter: Snow balances out the melting
what have rising temperature caused to the melting of glaciers and polar ice caps
Rising temperatures caused:
greater than average summer melting
reduced snowfall
what has been lost from Greenland + West Antarctica
Melting of small glaciers & polar ice caps projected MSLR ~ 0.5m
Melting of Greenland ice sheet projected MSLR ~ 7.2m
Melting of Antarctic ice sheet projected MSLR ~ 61m
what some impacts of MSLR
Effects: modifies propagation of tides & storm surges raises risks of extreme events
greater wave heights
greater wave driven run-up
Raised ground water levels
Salinised freshwater lens
what happens upon impacts of MSLR on wetland migration
Potential for landward migration & coastal squeeze across Gulf of Mexico estuaries (1.0 m sea level rise scenario)
landward erosion of seaward edge, new marsh is created in a retreated way.
if seawall is present infront of used land- ie farm, but nothing is protecting natural slatmarsh.. as sea levels rise this saltamarsh becomes SQUEEZES
Main contributors to SLR
thermal expansion, glacial melt and the melting of the Polar ice sheets.
Main impacts of MSLR
coastal inundation, flooding, wetland migration or loss, coastal erosion, saltwater intrusion and rising ground water tables
WHAT kind of management should be suggested for urban areas in coastal areas?
Adaptive management strategies for urban areas need to take into consideration both marine inundation and groundwater intrusion into their adaptive
what does historical SLR look like?
Large variations in sea level in the geological past
Recent changes driven by climate change
