Arctic sea ice hits annual maximum at near record low levels

 U.S. Fish & Wildlife photo
U.S. Fish & Wildlife photo (KTUU)
Published: Mar. 23, 2018 at 2:26 PM AKDT
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Arctic sea ice appears to have hit its maximum reach for the season on March 17, 2018, making this year the second lowest maximum in the 39-year satellite era. The four lowest maximum extents, during the satellite record, have all occurred in the past four years.

“The long term pattern showing less and less sea ice – both during the summer and during the winter – so this is occurring in all months of the year,” says Zach Labe, Ph.D. candidate in Earth Systems Science. “Not every single year is going to be a record low. There might be some years with more sea ice in the future than others, but the overall long term trend is loss of sea ice continuing.”

Sea ice

extent

is how much of the ocean is covered by sea ice, not the depth of the ice. Several factors influenced this year’s low sea ice growth. Both the Atlantic and Pacific sides of the Arctic had relatively stormy winters.

Southerly winds, during February 2018, brought warm air and ocean waters to the west coast of Alaska, which further impeded ice growth.

According to the National Snow and Ice Data Center, "This is the fourth winter in a row that such heat waves have been recorded over the Arctic Ocean."

Existing warm sea surface temperatures also made sea ice growth difficult.

"Especially the Bering Sea, sea surface temperatures south of the ice is also unusually warm," says Rick Thoman, climate science and services manager for the National Weather Service in Alaska. “It’s been warm in the Bering Sea, in many areas, for several years now. And that’s a contributor to low sea ice in the Bering, as well as persistent storminess.”

“Warm” is relative. In this case, it’s warm relative to “normal” temperatures.

“Most people would not want to go swimming in the Pribilofs right now," says Thoman. "Ocean surface temperatures – water temperatures are in the mid to upper 30s, which doesn’t sound that warm but is well above the freezing point of sea water, which is about 29 degrees Fahrenheit. You really have to work to cool ocean water 10 degrees. It doesn’t sound very warm, but when it comes to making sea ice that’s a big deal.”

The National Weather Service Ice Desk has put out the forecast for the next three months and says the ice in Norton Bay will likely not be shore-fast by the end of April. Furthermore, the water in that area will be ice free by the third week of May.

The total extent of the Arctic sea ice reached 5.59 million square miles, which is about 450,000 square miles less than the average and 20,000 square miles more than 2017.

Maximum north, minimum south: While the Arctic reached its maximum extent, the Antarctic reached its annual sea ice minimum in late February. The NSIDC says this year’s minimum extent was the second lowest in the satellite record. The extent for 2018 was 842,000 square miles. The lowest year on record, for Antarctic Sea, was 2017.