Minimum arctic sea-ice extent from 1979 to 2007.
Areas in risk of flooding.
Graph of trends. (Reference 11)
Greenland Ice sheet melt extent in 2002 and 2005.
There are two major driving forces behind sea level: global ice volume and thermal expansion.1-3. Thermal expansion is a result of warming ocean waters; as oceans heat up, they expand. Recent studies and advancements in technology have shown that for the period 1961-2003, thermal expansion was responsible for approximately 40% of the rise in sea level.2-4 The second and most widely known driving force behind changes in sea level is changes in global ice volume. The Greenland and Antarctic ice sheets make up most of the ice covering Earth’s surface.1. Ice sheet loss and shrinking alpine glaciers accounted for 60% of sea level rise from 1961-2003.4 Both driving forces are impacted by temperature – the warmer the earth becomes, the more sea level will rise.
Sea level rise is hard to predict, mainly because of the uncertainty in the rate and magnitude of changes in the Greenland and Antarctic ice sheets. The sea level projections in the 2007 IPCC Fourth Assessment Report provided the range of 18-59 cm by 2100. Unfortunately, this report did not include the most recent insights on melting ice sheets. According to the 2009 Copenhagen Climate Congress Synthesis Report, “the new observations of the increasing loss of mass from glaciers, ice caps and the Greenland and Antarctic ice sheets lead to predictions of global mean sea level rises of 1 m (±0.5 m) during the next century. The updated estimates of the future global mean sea level rise are about double the IPCC projections from 2007.”5
Rising sea level is most threatening to low lying island nations and the delta populations of South and Southeastern Asia, and the Nile Delta in Africa.6-8 Flooding in these regions will inundate low lying areas, impacting coastal infrastructure and agriculture while forcing people from their homes.6 Coastal habitats such as wetlands, deltas, salt marshes, mangroves and beaches will be impacted and may disappear if their movement inland is blocked by development.6-9 As sea levels rises, subsoil seepage of sea water will degrade freshwater resources and possibly cause salt damage to agricultural crops.10 These impacts, in combination with the other coastal and ocean impacts described on this website, could result in massive human migration away from inundated areas.6
