Scientists are getting significant help from the evidence of exciting marine life in Alaskan permafrost to reconstruct ancient changes in the ice cover over the Arctic Ocean.
Researchers and colleagues from Hokkaido University have discovered that the Beaufort Sea, on the margin of the Arctic Ocean, was not entirely frozen over during the coldest summers of the late Ice Age, some 12,800 years ago. The methodology these researchers used was ice wedges from the Alaskan permafrost that could help them further reconstruct historical sea-ice conditions in the Arctic Ocean, and as a consequent, improving forecasts for the future.
It has been long since scientists studied ice core samples from large permanent ice masses in the Antarctic ice sheet around the South Pole and Greenland near the North Pole. These samples have in them relics from the distant past climate such as dust particles, ions, sea salts, volcanic ash, and air bubbles, which tend to provide information on how the atmosphere of the Earth has changed over thousands and thousands of years.
A group of researchers led by Yoshinori Iizuka of Hokkaido University's Institute of Low-Temperature Science has discovered a way of investigating the geological history of areas near the north Arctic sea, which had previously been hard using standard techniques.
Present under the tundra of high northern latitudes in areas such as Canada, Russia, and Alaska is the layer of frozen ground which are permafrost. Permafrost contains massive wedges of ice that form when meltwater freezes in underground cracks. Iizuka and his colleagues investigated on concentrations in an ice wedge back in 2010 to belong to the late Pleistocene period, which represents the latter end of the last Ice Age some 14,400 to 11,400 years ago.
Apart from testing the levels of several ions in the ice wedges, the team also tested calcium sulfate, sodium, chloride, and bromide. The significant part of their research was how they determined that methanesulfonate (MS) ions in the wedges reliably indicated marine life activity, as they originated from oxidized dimethyl sulfide, a compound produced by plankton and ice algae attached to seasonal sea ice in the summer.
From 12,900 to 12,700 years ago, in the parts of the wedge representing the coldest periods of the late Pleistocene, MS ion concentrations were high. It revealed that, even during these coldest periods of the late Ice Age, the near-shore region of the Beaufort Sea near Barrow may not have filled by permanent ice, and that some open water existed in this area during the summers.
In their study in the journal Earth and Planetary Science Letters, the team concluded that further studies on sodium, MS, and bromide concentrations in other permafrost ice wedge would help scientists reconstruct the condition of the past Arctic sea-ice.
