Arctic Sea Ice Extent Continues Downward Trend

Arctic sea ice reaches the sixth-lowest summer extent since observations began nearly 40 years ago. Harsh ice conditions in the Canadian Archipelago and at the North Pole impeded the safe navigation of vessels.

As days are getting shorter across the Arctic the decline of sea ice has begun to slow down and the annual end-of-summer minimum is expected over the coming days. The center of the Arctic Ocean has already begun to refreeze while the edges of the sea ice are still experiencing limited melting.

Arctic sea ice extent, which traditionally hits its lowest figure during the middle of September, will likely come in at below 4.4 million square kilometers, making it the sixth-lowest since satellite observations began in 1979, researchers at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) confirmed.

This year’s ice melt follows the pattern seen over the past few years and will sit slightly below the figure of 2017 when ice cover had decreased to 4.7 million square kilometers. "The latest results confirm the worrying declining sea-ice trend in the Arctic, which we have witnessed for more than a decade," says Professor Christian Haas, Head of the Sea Ice Physics Section at the AWI.

Harsh Ice Conditions in Canada

The National Snow and Ice Data Center (NSIDC) in the United States also released figures on the ice extent minimum. As researchers use varying methods to interpret satellite data ice extent figures can differ slightly between different institutes. Researchers at NSIDC measured an ice extent of 4.6 million square kilometers on September 17 and indicated that a seasonal minimum "was imminent." Ice coverage was 1.69 million square kilometers below the long-term average from 1981-2010. The Arctic saw an unusually slow decline in ice during the month of July when cooler temperatures prevailed.

In contrast to previous summers, Canada’s Northwest Passage (NWP) was not ice free during 2018. Persistent ice conditions impacted a number of planned cruise and tourism operations in that part of the Arctic. As a result Canadian Coast Guard authorities declared an ice condition warning aimed at small pleasure craft. These types of vessels are increasingly venturing into the challenging waters of the NWP and have seen a 20-fold increase over the past two decades. Even larger, ice-capable vessels and cruise ships were required to rearrange their routes, including the Akademik Ioffe, the passenger vessel that ran aground at the end of August.

"Unlike in previous years, thick drift ice is hindering passage through the island world of the Canadian Arctic Archipelago," says sea-ice expert Lars Kaleschke from the University of Bremen.

Weather determines where the ice goes

Weather patterns continue to play a crucial role in the transport of ice across the Arctic Ocean. A high-pressure weather system over the Canadian Arctic Archipelago and the resulting ocean current funneled thick, multi-year ice into the Beaufort Sea and into the waters of the NWP. "At the same time, the air over the Canadian Arctic Archipelago in August was up to four degrees colder than the long-term monthly average. As a result, less ice melted in this region," emphasises Haas.

On the other side of the Arctic, Russia’s Northern Sea Route has been largely ice free for the past six weeks, but saw the most challenging ice conditions in seven years earlier during the summer. As a result, Russia’s icebreaker fleet had to extend winter navigation operations until the middle of July to assist vessels along the route. The waters of the Ob Bay were ice-covered into July for the first time in four years. Rosatomflot’s nuclear icebreakers assisted a number of vessels that had gotten stuck in the ice and safely escorted oil and natural gas carriers to and from the port of Sabetta.

Large annual and regional variations

Even though ice extent has decreased by about 40 percent compared to two decades ago ice conditions still vary significantly from location to location and from year to year. "There are still areas that are impassable, even for icebreakers. And places with a small sea ice extent this year could have considerably more next year, even though overall there is significantly less sea ice in the Arctic than there was 20 years ago," sums up Haas. While in previous summers the waters around the North Pole were partially ice-free, conditions were so challenging this year that the Swedish icebreaker Oden had to turn around before reaching the center of the Arctic Ocean. Such conditions had not been seen in at least 15 years the captain of the vessels explained.