Satellite data show potential for rapid melt of thicker, multiyear ice
FRISCO — After an average start to the Arctic sea ice melt season, the pace of melting picked up in July. By the end of the month, the sea ice extent was within 212,000 square miles of the extent recorded on the same date in 2012, and is now tracking below 2013 and 2014, federal ice trackers with the National Snow & Ice Data Center said in their latest monthly update.
The main reason the sea ice extent remained higher than in 2012 — the lowest year on record — was because of solid ice cover in Baffin and Hudson bays. In the Beaufort Sea, by contrast, the ice has now thinned considerably, with many large broken ice floes surrounded by open water.
For July, the ice trackers said the rate of sea ice melting has been pronounced, averaging 39,300 square miles per day, compared to 37,600 square miles in 2012 and 33,500 square miles per day in the long-term 1981 to 2010 average. This rapid loss is in part a result of fairly high air temperatures over most of the Arctic Ocean, according to the update.
Directly north of Greenland, temperatures reached nearly 11 degrees Fahrenheit above average. Cooler than average temperatures prevailed in the Barents Sea region. Through 2015, the linear rate of decline for July extent is 7.2 percent per decade.
The slow retreat of ice in Baffin and Hudson bays has affected local Native American communities as well as research projects in the region, according to the National Snow and Ice Data Center. These areas are normally accessible this time of year, but this year, a supply ship trying to reach coastal communities in Nanavut and Nunavik was delayed by three weeks. Extensive ice in the eastern part of Hudson Bay also resulted in delays of resupply for communities in Northern Quebec.
In their update, the NSIDC researchers also explained that the timing of ice melt is key to determining how much thick, multiyear ice will survive the summer. When the ice melt starts early, it leads to more areas of open water.
“The presence of open water surrounding the floes allows for enhanced lateral and basal ice melt, raising the possibility that much of the multiyear ice in this region will melt out during the remainder of the summer,” the monthly report says.
At the other end of the Earth, sea ice extent around Antarctica is the fourth-highest on record for this time of year, growing by about 58,000 square miles per day for the first half of July, then slowing to just 3,900 square miles per day for much of the rest of the month. Relatively warm conditions prevailed for much of the month in the two regions of ice edge retreat, the northern Weddell Sea and northwestern Ross Sea, with average air temperatures about 7 degrees Fahrenheit above average.
However, sea surface temperatures just north of the ice edge were 1 to 2 degrees Fahrenheit cooler than average, raising the potential for rapid ice growth through the remainder of the winter season.