Polar Ice-Caps & Sea-Level Rise

Scott Church
Climate Change 2001, Chap. 11: Changes in Sea-Level
Intergovernmental Panel on Climate Change, Working Group I
This is the chapter from the IPCC’s year 2001 Third Annual Report (TAR) that dealt with sea-level rise due to global warming. It is one of the most thorough compilations available regarding the state of knowledge on this subject as of that year. Apart from a few recent advances regarding polar ice-caps, most of its contents are still current.
Measurements of Time-Variable Gravity Show Mass Loss in Antarctica
Velicgna, I. and J. Wahr. 2006. Science, 311, (5768), pp. 1754 – 1756. DOI: 10.1126/science.1123785
This study used data from the Gravity Recovery and Climate Experiment (GRACE) satellites to determine mass variations of the Antarctic ice sheet during 2002–2005. The result is significant because the GRACE platform detects variations in total mass directly via their gravitational impacts, and as such its measurements are not subject to any of the noise sources or incomplete coverage area problems that affect most other studies. Velicgna and Wahr found a significant net mass loss for the Antarctic region which translates directly into rising sea-levels. Their results are in good agreement with those obtained by most other studies of the region.
Antarctic Climate Change During the Last 50 Years
Turner et al. 2005. Int. J. Climatol. 25, pp. 279–294. DOI: 10.1002/joc.1130
This study from a team led by John Turner of the British Antarctic Survey used data from the Reference Antarctic Data for Environmental Research (READER) project to investigate trends in monthly mean near-surface temperature, mean sea-level pressure (MSLP) and wind speed for the Antarctic continent over the last 50 years. The data came from a network of 19 stations at different locations where long-term records are available. They found major increases in warming during this period on the Antarctic Peninsula and slight cooling around the continental rim, consistent with activity of the Southern Hemisphere annular mode (SAM), which has been shifting Antarctic surface warming toward the Peninsula in recent decades.
Recent dramatic thinning of largest West Antarctic ice stream triggered by oceans
Payne et al. 2004. Geophys. Res. Lett. 31, (L23401), DOI: 10.1029/2004GL021284
A growing body of evidence suggests that the Pine Island Glacier, which is the primary drainage path for the West Antarctic Ice Sheet (WAIS) is changing on decadal or shorter timescales. This model-based study suggests that these changes are being driven by the surrounding ocean. A warmer ocean can contribute to melting on the underside of glaciers at their point of contact with the ground (or basal melting). This in turn can lubricate the glacier’s underside and speed up its rate of movement and eventually make it unstable. As global warming is known to be affecting the oceans here and around the world, these results add to the body of evidence suggesting that instability of the WAIS and other ice sheets around the world may be accelerating in unexpected ways. If so, this raises the possibility of sudden and possibly even catastrophic sea-level changes during the coming century that are not on the horizon today.
Antarctic Heating and Cooling Trends
NASA Goddard Institute for Space Studies
These links show color plots of surface temperature trends for the Antarctic continent from 1982 to 2004 as measured by the Advanced Very High Resolution Radiometer (AVHRR) package on NOAA’s Polar Orbiting Environmental Satellite (POES) series and supplemented with other in-situ surface temperature measurements. They reflect a warming in the surrounding ocean and coastal rim and a cooling of the Antarctic interior, both of which are expected from the net impacts of global warming, ozone depletion and resulting changes in the Southern Annular Mode (SAM) and oceanic currents circumventing the South Pole. One of these impacts that is likely contributing to the interior cooling is an increase in snowfall due to rising oceanic temperatures and atmospheric moisture content in the surrounding ocean.
The Greenland Ice
How much future sea level rise? More evidence from models and ice sheet observations
These articles from RealClimate discuss some of the latest discoveries about the net contributions of the Greenland and Antarctic contributions to global sea-level rise, including the fact that breakup of the Greenland ice-sheet now appears to be accelerating. The second one includes discussions of a few of the papers linked below. Since its publication another study (Luthcke et al. 2006) has independently reached similar conclusions to one of the studies they discuss (Rignot & Kangaratnam, 2006) using different methods. Both of these papers are linked below.
Changes in the Velocity Structure of the Greenland Ice Sheet
Rignot, E. and P. Kanagaratnam. 2006. Science, 311, (5763), pp. 986 – 990. DOI: 10.1126/science.1121381
This year 2006 mass balance study of the Greenland continent by Rignot and Kanagaratnam combined satellite interferometry measurements of coastal glacier motion with modeled-based and observational estimates of mass buildup of the interior plateau (including meltwater runoff). They found widespread glacier acceleration resulting in a net mass loss that has been accelerating since at least 1996, increasing Greenland’s contribution to global sea-level rise.
Recent Greenland Ice Mass Loss by Drainage System from Satellite Gravity Observations
Luthcke et al. 2006. Science, 314, (5803), pp. 986 – 990. DOI: 10.1126/science.1130776
This year 2006 mass balance study of the Greenland continent by Rignot and Kanagaratnam combined satellite interferometry measurements of coastal glacier motion with modeled-based and observational estimates of mass buildup of the interior plateau (including meltwater runoff). They found widespread glacier acceleration resulting in a a net mass loss that has been accelerating since at least 1996, increasing Greenland’s contribution to global sea-level rise.
Recent Ice-Sheet Growth in the Interior of Greenland
Johannessen et al. 2005. Science, 310, (5750), pp. 1013 - 1016. DOI: 10.1126/science.1115356
This year 2005 satellite interferometry study found that Greenland’s interior plateau was growing due to increased precipitation which in turn, was related an up-cycle in the North Atlantic Oscillation (NAO). Since it was first published global warming skeptics have been citing it as proof that Greenland is not contributing to sea-level rise, and carefully avoiding mention of the fact that it concentrated on the Greenland interior only and not the coastal areas where there have been larger losses during most of the study period examined (see the other studies linked on this page).
Arctic Sea Ice decline in the 21st Century
This article from RealClimate discusses what is currently known about the future of sea-ice in the Arctic. A declining Arctic sea-ice pack will have severe impacts on wildlife such as polar bear populations, which depend on the annual sea-ice season for access to seals (a primary food source). Arctic sea-ice also plays an important role in regulating the thermohaline circulation of the world’s oceans, and through it regional climates around the globe.
Sea-Level Rise
Sea Level, Ice, and Greenhouses--FAQ
Robert Grumbine
This is a reprint of a 1997 contribution to the SCI-Environment newsgroup by Robert Grumbine of the NOAA NCEP Marine Modeling and Analysis Branch in Camp Springs, MD. Though somewhat dated in terms of the most recent developments in polar ice-cap trends, it gives an excellent, and very readable overview of sea-level rise and its relationship to the Greenland and Antarctic ice sheets.
Sea-Level Rise & Global Climate Change: A Review of Impacts to U.S. Coasts
Pew Center on Global Climate Change, February 2000
This year 2000 report from the Pew Center on Global Climate Change reviews the potential impacts to coastal U.S. communities from the most likely sea-level rise scenarios for the coming century.
Coastal Zones and Sea Level Rise
U.S. Environmental Protection Agency
Sea Level Rise Maps
U.S. Environmental Protection Agency
Sea Level Rise Reports
U.S. Environmental Protection Agency
These pages from the EPA provide a number of reports summarizing governmental and academic research on sea-level rise due to climate change, including maps of predicted coastline changes.
Sea Surface Height Visualizations
Goddard Institute for Space Studies
0-6 m Sea Level Rise Maps by Region
Center for Remote Sensing of Ice Sheets – U.K.
Animated impacts of sea-level rise on U.S. coastal cities
National Environmental Trust
Most estimates of global warming related sea-level rise for the coming century are on the order of 0.3 to 0.7 meters. Many people find it difficult to believe that sea-level changes this small could be as damaging as experts believe they will be (a fact that global warming skeptics gleefully capitalize on in their editorials and publicity campaigns). The confusions stems from the fact that global warming impacts manifest themselves as increases in global average sea-level—which is very different from regional sea-level change, particularly in coastal areas and during storm surges. In fact, sea-level change is a complicated process involving thermal expansion due to local temperature, localized gravitational effects, regional ice and water mass balance, and even local atmospheric pressure. These pages provide animations of the evolution of regional sea-level over time (in Quicktime and/or Windows Media formats). The first is the GISS Scientific Visualization Studio sea-level map page which provides a number of animations of sea surface height anomalies over periods of one to two years as measured by the TOPEX/Poseidon satellite and other satellite-based and model products. Variations shown range from +/- 0.3m to +/- 0.5m depending on the clip. The second shows static images and animations of costal inundation areas by region for sea-level increases of 1m to 6m. The final page from the National Environmental Trust provides animated inundations for a number of U.S. coastal cities that would result from 0.6m to 0.7m of sea-level rise combined with 100-year and hurricane level storm surges. These videos dramatically illustrate that sea-level change is anything but globally uniform and that small changes in the global average mask large, and potentially very destructive impacts in many populated coastal regions.
Northern Atlantic Cycles
North Atlantic Oscillation
Lamont-Doherty Earth Observatory, Columbia University
The North Atlantic Oscillation (NAO) is a large scale seesaw in atmospheric mass between a subtropical region high and a polar region low that is the dominant mode of winter climate variability in the North Atlantic and much of Greenland. It fluctuates on time scales that vary from one to several years and accounts for a great deal of regional cooling in these areas that is often cited incorrectly as proof that global warming is not happening. This page from Columbia University’s Lamont-Doherty Earth Observatory gives an overview of the NAO with some very informative graphics of the most salient features in its cycles.
NOAA Hurricane forecasts & the Atlantic Multidecadal Oscillation
This discussion at RealClimate by Thomas Crowley of Duke University’s Earth and Ocean Sciences Division discusses the potential impacts of the Atlantic Multidecadal Oscillation (AMO) on global warming and the recent upsurge in Atlantic tropical cyclone activity. The AMO is a 50-80 year timescale cycle in North Atlantic ocean-atmosphere variability that has been inferred from statistical analyses of observational and proxy climate data, climate model simulations. It is believed by some to describe some of the observed early 20th century (1920s-1930s) high-latitude Northern Hemisphere warming and some, but not all, of the high-latitude warming observed in the late 20th century. In recent years it has garnered much attention because global warming contrarians are now attributing most or all 20th century Northern Hemisphere temperatures to it in an attempt to dismiss global warming as “natural variability”. Data on it is scant, as reliable records span no more than 2 of its cycles. Various theories of it causes have been advanced, but as of this writing there is no solid evidence that it has any real physical basis (see the link below).
Atlantic Hurricane Trends Linked to Climate Change
Mann, ME & KA Emanuel. 2006. EOS, 87, (24), pp. 233 - 244
This article from Mann and Emanuel presents the results of their statistical analysis (One of the most thorough of its kind on this subject) that evaluated the correlations of 20th century climate change with various known natural cycles, including the AMO. They found that when other factors are accounted for, the AMO “signal” reduces to red noise. This shows that it is likely to be a statistical anomaly with little or no physical meaning for climate change. This essentially pulls the plug on contrarian claims that it explains away global warming.


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