// lecture 04 Flashcards
sea level rise since 1880 has been about:
225 mm (22 cm or ~9 in)
these don’t contribute to sea level rise:
sea ice and ice shelves (connected to ice sheets, but floating on ocean).
these contribute to sea level rise:
- thermal expansion of sea water - water expands when it warms and is the main contributor of sea level rise so far.
- mountain glaciers.
- ice sheets (Greenland and Antarctica).
contribute only a tiny amount to sea level rise:
permafrost and snow cover.
natural influences on sea level:
tides, ocean currents, winds, tectonic activity (some are rising/falling).
tide gauges
are measuring sticks or sometimes floats in wells. always coastal and few long records.
TOPEX
Poseidon Radar Altimetry - instruments emit a short radar flash and measures the time-of-flight of its reflection from Earth 1,000 times per second. Measures sea level and ice sheet height.
addition of heat and addition of freshwater (land ice melting mostly) =
total sea level rise.
sea level rise 1993-2010 IPCC AR5:
thermal expansion 39%, mountain glaciers 27%, Greenland 12%, Antarctica ice sheet 9%, land water storage 13%, total 100%.
thermal expansion and mountain glaciers account for 2/3 of total sea level rise for this year period as well.
measuring the global oceans:
addition of heat (Argo) + addition of freshwater (Grace) = total sea level rise (Jason).
Exendable Bathyermographs (XBT)
helps monitor the ocean heat content. about 70 voluntary ships toss them overboard, about 14,000 each year. they measure down to 1500 m and have been in use since 1962.
the base of much of Greenland’s ice is
below sea level. was ice free about 15 million years ago when CO2 was 400-500 ppm.
Greenland ice is equivalent to a
~7 m rise in global sea level.
Mountain glaciers currently contribute
27% to rising sea levels. Greenland and Antarctica currently contribute 21%.
Recent estimates of sea level rise including increases in calving:
- 0.5 - 1.4 m by considering past SLR to past warming dependence and used IPCC estimate of future warming.
- accelerated but plausible dynamic thinning could give 0.8 - 2 m.
current best estimate for 2100 global sea level
will rise by 0.8 m. assumes business as usual, depends on location, and has an uncertainty of 30% or so.
sea level rise is a very slow process.
takes an extremely long time to melt Greenland/Antarctica. In the long term, ice sheets will be the main problem, but this will take centuries to happen completely. In some places it has already started.
11 of the 15 largest cities are
along coasts or estuaries.
Population of people living with 1 m of sea level:
around 150 million.
costs of sea level rise:
wetland loss, salinization of aquifers/crops, constructing barriers, and relocation.
