|from NASA to see animation click|
These estimates of sea level rise are based on the amount of warming experienced by the plant in response to the increase in greenhouse gases that has already occurred. Even if the entire planet stopped burning fossil fuels tomorrow, the planet would continue to warm. Whatever is going to happen will happen; it is too late to change that. Warming increases sea level in two ways: thermal expansion and the melting of the glaciers and ice caps. When water warms it expands in volume and is expected to contribute a portion of the sea level increase. More than 97% of the Earth’s water is already within the in oceans. The remaining 2.8% of water is the water within the land masses, 2.15% is contained in icecaps and glaciers. The melting of the ice, which has so far been most pronounced in mountain glaciers might increase surface infiltration of water, but the remainder will flow to the oceans increasing sea volume. The big concern is for the future of the ice sheets in the Arctic and Antarctica and what impact the volume of water contained there will have on sea levels.
Last Friday the sea ice minimum analysis produced at NASA’s Goddard space laboratory using satellite data was released. The melting of sea ice in the Arctic reaches its annual minimum, when the ice cap covers less of the Arctic Ocean than at any other period during the year, in the middle of September each year. The good news is that NASA is predicting it is unlikely that this year’s summer low will break a new record. Still, this year’s melt rates are in line with the long term decline of the Arctic ice cover observed by NASA and other satellites over the last several decades. The data record, which began in November 1978, shows an overall shrinking in the size of the Arctic sea ice minimum each summer since 1978 of 14% per decade.
The ice cover in the Arctic Ocean was measured at 2.25 million square miles on Aug. 21. For comparison, the smallest Arctic sea ice extent on record for this date, recorded in 2012, was 1.67 million square miles, and the largest recorded for this date was in 1996, when ice covered 3.16 million square miles of the Arctic Ocean. Though, early summer saw a fast retreat of the sea ice, melting slowed as clouds over the central Arctic kept temperatures cooler than average, and the Arctic experienced mild summer storms. According to Walt Meier, a glaciologist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland: “Last year’s storm went across an area of open water and mixed the smaller pieces of ice with the relatively warm water, so it melted very rapidly. This year, the storms hit in an area of more consolidated ice. The storms this year were more typical summer storms; last year’s was the unusual one.”
In Antarctica, the story is different. Right now, Antarctic sea ice is in the midst of its yearly growing cycle and is heading towards the largest extent on record. Antarctic sea ice reached 7.45 million square miles on Aug. 21. In 2012, the extent of Antarctic sea ice for the same date was 7.08 million square miles. The phenomenon, appears counter-intuitive, and is currently the subject of many research studies. Still, the rate at which the Arctic is losing sea ice surpasses the speed at which Antarctic sea ice is expanding so sea level rise is of great concern to mankind who throughout history has settled along the coast lines.