Lect 7 Flashcards
Reconstructing sea level change
•Stratigraphy & Oxy. Isotopes (Geol time scale) •Raised reefs, coral, stalagmites (Inter/Glacial scale) •tide gauges/satellites (Last 200 years)
Deglaciation-Sea level change
Meltwater released from proglacial lakes;
E.g MWP1a ~14kBP. 25m rose in 500 years.
E.g Younger Dryas = Lake Agassiz meltwater release
Corals as a proxy
-corals grow on top of each other within 5m of ocean surface
—> can be U-TH and Radiocarbon dated
Barbados Record: LGM = 120m fall
-rates match insolation record
-delta 18O decr. that matches sea level rise
IMPLIES N.HEMI INSOLATION = DEGLACIATION CAUSE
MWP1a
Meltwater Pulse 14k BP
-far field proxies suggest Antarctic origin, IRD event?
8.2ka event
Cooling event within stable interglacial Holocene
=v.large meltwater release into N.Atlantic = 0.5m rise in 2 days = THC/AMOC shutdown + cooling
Climate driven change
Mass balance: add water = rise, remove water = fall
Steric: temperature and salinity
Relative Sea Level
Change due to EUSTASY+ISOSTASY+TECTONICS
Eustasy
Water volume related
Glacio-eustasy
Tecto-eustasy
Isostasy
Land mass related
Glacio-isostasy
Hydro-isostasy
Characteristic curves
Near field sites
Ice margin sites
Intermediate sites
Far field sites
Best site for RSL reconstruction
Far field site (Barbados)
- away from ice sheet
- tectonically stable
Sea level fingerprinting
Modelling sea level change from melting of different ice sheets due to effect of gravity on sea level
-sea levels fall closest to ice sheets
UK sea level
Isostatic Effect
Seesaw:
Northern UK= glacio-eustatic rebound due to unloading= falling Rel.sea level
Southern UK= rising rel. sea level
Stochastic behaviour
Mid 2010 = 7mm sea level drop?
Water all went into Lake Eyrie basin, Aus
Evidence: GRACE satellites
