Sea Level & Ice Sheets Concern about the Future of Inhabited Coastlines Presented by Julie Brigham-Grette and Beth Caissie (thanks to Ken Miller, Rutgers, for many of.
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Sea Level & Ice Sheets Concern about the Future of Inhabited Coastlines Presented by Julie Brigham-Grette and Beth 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 Sea level history over the past 450,000 years Source: Labeyrie et al (2003) In: Paleoclimate, Global Change and the Future, Springer. Last interglacial Full Glacial Global Sea Level Lambeck et al., 2002, based on tropical & subtropical records TODAY Ice from the Ocean makes ice sheets, so sea level drops When Ice sheets melt, sea level goes up. Antarctica West East Processes below Floating Glacier Terminus Should I Sell My Shore House? How long will it take to achieve Gore World 5 m rise? = sea level at last major interglacial 125,000 y ago: IPCC2001: 300-700 years; IPCC2007 700-1000 yr New: Greenland surging much sooner, but >>100 yr Otto-Bleisner et al. (2006) simulation 2007 2300 2700 3200 3800 125,000 y ago last interglacial The future: IPCC Brazil Atlantic City NJ Observations (Tide Gauge and Satellite Altimetry Data) •Overall 10-20cm rise in 20th century •Accepted value of 1.7±0.3mm/yr 20th century •1950-2000 1.8±0.3mm/yr Fi g ur e 5 . 1 3 Accelerating Sea Level Rise (1993-2003) JPL NASA http://www.climateaudit.org •Rate of sea level rise from 1993-2003 accelerated to 3.1±0.7 mm/yr •Sea level rise varies spatially •Western Pacific and Eastern Indian Ocean have seen the largest fluctuations in sea level due to increased average sea level coupled with ENSO events Causes of Sea Level Rise • Melting of glaciers, ice caps, ice sheets • Thermal expansion of sea water • Small scale changes due to anthropogenic land water storage (damming rivers, over-pumping of water and fuels, wetland and forest destruction) • Relative changes in sea level due to tectonic movements (land subsidence or rebound) Why Is Global Sea Level Is 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 Melting Glaciers & Ice Caps: Melting land ice adds to ocean volume, but not sea ice Alpine IPCC2001 Cartoon x-section of ice sheet Why Is Global Sea Level Is Rising Today? . Melting Mountain Glaciers and Ice Caps: Alpine glaciers 0.6 mm/yr Greenland Ice Cap IPCC2001: near 0 Cazenave & Nerem (2004): >0.15 mm/yr New data: increased from 0.23 mm/y 1996 to 0.57 mm/y 2005 (Sterns & Hamilton 2007) 2005 2007 Greenland Mass Balance Estimates SWIPA II, 2009 Higher CO2: Predicted Global Warming IPCC Third Assessment Report: Climate Change 2001 Synthesis Report IPCC Fourth Assessment Report 2007 Sea-Level Forecast: IPCC 2001 & 2007 40 cm (1.25 ft) rise by 2100, 1 m (3.3 ft) by 2200 IPCC 2001 error estimate: 20-80 cm IPPC 2007 error: 20-60 cm (does not include ice sheet melting) 2001 2007 http://www.realclimate.org/images/sealevel_1.jpg We are tracking high end predictions Thermal expansion greater: ‘93-03 data 1.6 m/myr Increase in heat W/m2 Willis et al. (2004) Not IPCC2007 40±20 cm Best estimate 80 cm global; max. 1 m can’t be rules out Rahmsdorf et al. (2007) Sea level rise data from Guilford, CT Sea level rise data from around the world Long Beach Island, NJ Human stabilized Natural movement 400 m Courtesy N. Psuty 80 cm-1m in 100 yrs with subsidence making it worse in some places Insurance Rates? Disaster relief? Both need forecasting and planning Bangladesh: 17 million displaced 22nd century Ammerman & McClennen 2000 Where Al got it wrong Greenland (= 6 m of sea level) is thinning now But did not disappear during the last Interglacial How a 1 m rise of sea level will affect the Nile Delta Would impact 6.1 Millon people 4500 km2 cropland a small rise of sea level across a low lying coastal plain translates into a significant advance of the sea or retreat of the shoreline former Sea Level Rise new Coastline O cean ViewH otel Coastline former dunes new beach / new Sea Level former Sea Level coastal environments retain their original profile as they “roll” landward with rising sea level p. 179 new Mainland Coast new Bay or Lagoon Marsh and Tidal Mudflats new Dunes new Beach former Dunes former Beach new Sea Level former Sea Level Exercise: Rates of Sea Level Change Future projections Mitigating Risks (jig saw issues)