Arctic Sea Ice at Minimum Extent based on Satellite Record
This past decade has been concerning for researchers studying Arctic sea ice, but not nearly as alarming and astonishing as the past several months. The National Snow and Ice Data Center (NSIDC) on September 16, 2012 released preliminary data on the annual summer extent of the Arctic sea ice coverage. These data support the predicted annual trends of sea ice extent decreasing rapidly. Sea ice extent measured at an annual minimum has been steadily declining by approximately 10% per decade, since the beginning of the satellite record. This year’s data put out by the NSIDC only confirmed the trend once again.
“There continues to be considerable inter-annual variability in the sea ice cover, but the long-term retreat is quite apparent”, said Claire Parkinson for NASA in NSIDC’s September press release.
Climate science is an inter-disciplinary field of study which includes research in geology, oceanography, atmospheric chemistry, and earth sciences. Climate change is indeed a hotly debated topic, with lively discussions in both academic literature and in popular news. Some of the most visible and indisputable evidence is the record of the melting of the world’s glaciers and the receding of the Arctic sea ice which covers the North Pole.
Approximately 3.4 million square kilometers was reported as covering the North Pole and Arctic Sea. These are preliminary data which don’t necessarily account for the complexities of regional weather, wind patterns, and ocean currents, but the implications of these data are not to be taken lightly.
In an earlier August press release from NASA which echoes the recent news, research scientist Walt Meier stated "…in the context of what's happened in the last several years and throughout the satellite record, it's an indication that the Arctic sea ice cover is fundamentally changing."
There are many different types of scientific records of earth’s past climate. The NSIDC is only one entity which provides data products to scientists, researchers, and the public. They receive data from NASA and Defense Meteorological Satellite Program satellites. NASA’s ‘IceSat’ operational from 2003-2009 collected some of the historic satellite data NSIDC uses to compile its data products, while the ‘Aqua’ is now orbiting above, gathering more data. The European Space Agency maintains ‘Cryosat2’ which is a satellite specifically dedicated in its mission – to monitor sea ice thickness and the glacial ice sheets of the Arctic, Antarctic, and Greenland. Researchers at the University of Washington’s Polar Science Center and Applied Physics Laboratory are working to develop another system, the Pan-Arctic Ice Ocean Modeling and Assimilation System, known as PIOMAS, to study Arctic sea ice. Both PIOMAS and NSIDC/NASA validate their data products through ‘ground truth’ measurements, often referred to as measurements taken ‘in situ’ or ‘in place’. Undersea sonar instrumentation, US Navy submarines, and aerial flyovers with NOAA planes are all used to verify and calibrate satellite data. Models and research using PIOMAS attempt to take into consideration more factors besides total ice coverage, such as ice thickness and volume, as well as other oceanographic and meteorological dynamics which influence Arctic ice. Even if sea ice extent is the target of research, measurements of thickness are necessary, which is why it’s valuable to have research being conducted with different systems and datasets. As the quote below explains, receding ice cover isn’t the only factor to consider, but ice age and thickness are crucial to a balanced understanding.
"The core of the ice cap is the perennial ice, which normally survived the summer because it was so thick", said Joey Comiso, senior scientist with NASA Goddard. "But because it's been thinning year after year, it has now become vulnerable to melt".
The record of the past demonstrates that there has been thick, year round ice, which prevents dramatic decreases in the summer extent like this year. Indeed there are many considerations to take into account when studying the Arctic, one of which is the concept of the ‘Ice-albedo Effect’. This is a concept also referred to as ‘Ice-albedo feedback’. This is a positive feedback loop, which explains how with the more ice melting that occurs, the faster the rate of melting increases. As less ice covers a surface like water, it becomes darker. Darker colors absorb more light, and therefore less solar energy is reflected (as lighter colored ice or snow can do), and as a consequence increased heating occurs. This can work in both ways to cool or heat a surface. This effect means that the slightest warming and melting is amplified.
As crucial to understanding the relevance of Arctic sea ice extent in relation to global climate change, is the fact that Arctic climate helps regulate global climate. Although it’s true that the Antarctic may be accumulating new ice and snow, the warming Arctic climate and melting sea ice are far more important to earth’s whole climate by comparison as explained in an NSDIC factsheet.
“…Sea ice near the Antarctic Peninsula, south of the tip of South America, has recently experienced a significant decline. The rest of Antarctica has experienced a small increase in Antarctic sea ice.
Antarctica and the Arctic are reacting differently to climate change partly because of geographical differences. Antarctica is a continent surrounded by water, while the Arctic is an ocean surrounded by land. Wind and ocean currents around Antarctica isolate the continent from global weather patterns, keeping it cold. In contrast, the Arctic Ocean is intimately linked with the climate systems around it, making it more sensitive to changes in climate.”
The head of University of Calgary’s geology department, professor John Yackel in a recent press release details some of the likely effects of retreating Arctic sea ice in the quote below. The overwhelming consensus is that Arctic sea ice is disappearing – the question then becomes, what can we do about it?
“When there’s no longer that sea ice below the air mass and it’s just open ocean, that’s when more moisture off the ocean’s surface gets into the atmosphere and the water vapor in the atmosphere makes for more violent storms... We can also expect to see an increase in storm frequency and storm intensity for most of the world’s populated places as the Arctic and Earth continues to warm.”
NASA September press release: http://www.eurekalert.org/pub_releases/2012-09/nsfc-asi091912.php
NASA August press release: http://www.eurekalert.org/pub_releases/2012-08/nsfc-asi082712.php
NSIDC fact sheet: http://nsidc.org/cryosphere/quickfacts/seaice.html
University of Calgary Press Release: http://www.ucalgary.ca/news/utoday/september24-2012/melting
NSIDC Source: http://nsidc.org/news/press/20121002_MinimumPR.html
Image Credit: NASA