Sea Level & Ice SheetsSea Level & Ice SheetsConcern about the Future of Inhabited CoastlinesConcern about the Future of Inhabited Coastlines

Presented byPresented byBeth CaissieBeth Caissie

(thanks to Ken Miller, Rutgers, for many of his slides)

Sources: Petit et al. (1999) Nature 399, 429-436 and National Oceanic and Atmospheric Administration (NOAA), USA

Source: Labeyrie et al (2003) In: Paleoclimate, Global Change and the Future, Springer.

Sea level history over the past 450,000 years

Lambeck et al., 2002, based on tropical & subtropical records

TODAY

Last interglacial

Full

Gla

cial

Global Sea Level

Ice from the Ocean makes ice sheets, so

sea level drops

When Ice sheets melt,

sea level goes up.

Antarctica

West East

Why Is Global Sea Level Rising Today?

.

Melting Ice Caps and Glaciers:• Melting land ice adds to ocean volume (sea ice does not)

• Greenland is thinning today, but didn’t disappear during the Last Interglacial• IPCC2001: near 0• Cazenave & Nerem (2004): >0.15 mm/yr

• Sterns & Hamilton (2007): 0.57 mm/y

Muir Glacier

1941, William Field

2004, Bruce Molnia

From the Glacier photograph collection. Boulder, Colorado USA: National Snow and Ice Data Center/World Data Center for Glaciology.http://nsidc.org/data/glacier_photo/repeat_photography.html

Glacial Retreat•Most glaciers world-wide are in retreat•Alpine glaciers contribute 0.6 mm/yr to sea level rise•Why are some advancing?

•Increased snow

Why Is Global Sea Level Rising Today?

Why Is Global Sea Level Rising Today?Thermal Expansion:

• ocean has gained heat

• Warmer water less dense global 20th century warming ~0.6°C • 1.6 mm/yr sea-level rise

Brazil

Atlantic City NJ

Should I Sell My Shore House?Should I Sell My Shore House?

Fi gure 5. 13•Overall 10-20cm rise in 20th century•20th century average rate of sea level rise: 1.7±0.3mm/yr •1950-2000 1.8±0.3mm/yr•1993-2003 accelerated to 3.1±0.7 mm/yr

ObservationsObservations(Tide Gauge and Satellite Altimetry Data)(Tide Gauge and Satellite Altimetry Data)

Sea-Level Forecast: IPCC 200740 cm (1.25 ft) rise by 2100

1 m (3.3 ft) by 2200 IPCC 2007 error: 20-60 cm (does not include ice sheet melting)

http://www.realclimate.org/images/sealevel_1.jpg

2007

Recent Global Sea Level Rise Estimates

Del

ta C

omm

.

WB

GU

Data

Data:Church and White (2006)Scenarios 2100:50 – 140 cm (Rahmstorf 2007)55 – 110 cm (“high end”, Delta Committee 2008)Scenarios 2200:150 – 350 cm (“high end”, Delta Committee 2008)Scenarios 2300:250 – 510 cm (German Advisory Council on

Global Change, WBGU, 2006)

Slide from Rahmstorf web site

Best Estimate = 80 cm of SL Rise by 2100, 1 m is not out of the question

Human stabilized

Natural movement 400 m

Long Beach Island, NJ

Courtesy N. Psuty

http://www.learnnc.org/lp/editions/cede_smsandvol/323

Sea Level Rise – like this?No !

Gradual sea level rise and storm events causing this?Highly likely!

(from Day After Tomorrow)

The Nile River Delta

1 m SL Rise would impact

6.1 Million people

4500 km2 cropland

http://www.geo.umass.edu/stategeologist/frame_maps.htm

Boston