On thin ice: As Arctic Ocean warms, a scramble to understand its weather
Increasing summer ice melt in the Arctic Ocean could shift global weather patterns and make polar waters more navigable. But scientists say forecasting Arctic ice and weather remains a massive challenge.
Boston — The prospect of more ice-free water during Arctic Ocean summers has triggered efforts to improve ice and weather forecasts at the top of the world.
Much of the research into the interplay between the ocean, ice, and atmosphere has centered on global warming and the long-term changes it will impose on the Arctic – including a continued decline in summer sea ice. Researchers are exploring the impact that decline could have on seasonal climate and weather patterns at lower latitudes.
Declining summer sea ice, however, is also expected to lead to an increase in commercial fishing, oil exploration, cargo-ship traffic, tourist cruises, and other activities where short-term weather and ice forecasts are vital to reducing the risks of operating in the 5.4 million square mile ocean.
Among those anticipating increased activities above the Arctic Circle are the US Navy and Coast Guard. But in a report to Congress nearly two years ago, the Defense Department identified "shortfalls in ice and weather reporting and forecasting" as one of several key challenges to future operations there.
Currently, the US National Ice Center – based in Washington and run jointly by the Navy, Coast Guard, and the National Oceanic and Atmospheric Administration – issues Arctic ice forecasts for conditions expected within a day or two, says Pablo Clemente-Colon, the center's chief scientist.
But in a clear sign that a day or two isn't enough, "one of the requirements we recently received from the Coast Guard is to get seven-day forecasts of sea-ice conditions so they can properly plan operations," Dr. Clemente-Colon says.
All this has a familiar ring to veteran Arctic scientists.
Ice forecasts were "an important element during the Cold War," says Axel Schweiger, a polar scientist at the University of Washington's Applied Physics Laboratory in Seattle. Back then, US and Soviet nuclear submarines stalked one another in an ocean basin seen as a prime area for launching sub-based, nuclear-tipped ballistic missiles.
But interest in Arctic sea-ice forecasts waned when the Cold War ended, only to return with concerns about the effects of global warming.
In 2007, when the summer melt season ended in mid-September, the extent of summer ice reached its lowest point in the satellite record, which goes back to 1979.
The '07 record didn't last long. In 2012, the melt-back of summer ice broke the '07 record – in the middle of the melt season. By the end of the season the extent of summer sea ice was 18 percent below the 2007 figure. The surviving ice patch – some 1.4 million square miles of it – had anchored one edge to the northern coasts of Greenland and Canada's Arctic Archipelago, leaving several hundred miles of open water between its seaward edges and the remaining Arctic coastlines of North America, Europe, and Asia.
The extent of melting in 2007 "caught pretty much everybody by surprise, because the retreat of the ice cover that summer was quite extreme," says Martin Jeffries, program officer and science advisor to the Office of Naval Research's Arctic and Global Prediction Program.
Despite the initial shock, however, the record melts of '07 and '12 arrived in the context of a persistent decline in summer sea ice throughout the 24-year satellite record.
The potential for a significant increase in maritime traffic in the Arctic basin each summer demands a better understanding of the ice cover and the factors that affect it in order to improve predictions.
Summer storms, for instance, can have a profound effect on the ice. Last summer provided a textbook example. A storm dubbed the Great Arctic Cyclone of 2012 moved into the central Arctic Ocean from Siberia Aug. 4 – the most powerful August storm on record for the Arctic Ocean. The storm packed winds of more than 30 miles an hour in some areas of the Arctic Ocean above the Pacific and lingered over the ocean for a few days before petering out.
For 10 days, the pace of ice loss accelerated, reducing the extent of summer ice by nearly 60,000 square miles. The heaviest losses appeared from the Beaufort Sea above Canada and Alaska west to the East Siberian Sea.
A team led by the University of Washington's Jinlun Zhang, a researcher with the university's Applied Physics Laboratory, analyzed the storm's impact via modeling studies.
From Aug. 6 to Aug. 8, the researchers say the ice underwent an "unprecedented" loss of volume of 12.9 percent.
The mechanism? Wind from the storm essentially turned already-thin pack ice into a giant Mix Master as it blew across the pack's rough surface. As floating pack ice slowly moved, the ice's rough underside stirred to the surface relatively warm water typically held at bay by an upper layer of colder water. The warmed water melted the ice from below, the study indicates.
Thin pack ice is vulnerable to wind and waves, which break it into smaller floes that are more easily carried off by the winds.
In the end, the loss of ice the storm triggered amounted to only 4.4 percent of the season's total loss, so the season's decline would have set a record even without the storm, the researchers say.
Others had speculated that the impact storms have on melting contribute to sea-ice decline, says Dr. Schweiger, who took part in the study, published last month in the journal Geophysical Research Letters.
"We showed the effect on the ice, and processes like that of course will make a difference for shorter-term forecasts," he says.
The event highlights another factor critical to ice forecasts, notes the National Ice Center's Clemente-Colon.
"To get any improvement in ice forecasting, you really have to improve weather forecasting in the Arctic," he says. Among other things, that means more weather sensors in a sensor-starved part of the world.
To help fill that gap, NOAA inked an agreement last year with the oil industry to share forecast-relevant data from instruments on oil and gas platforms, Clemente-Colon says. The agreement is similar to a pact the two have covering for data from platforms in the Gulf of Mexico gathered above and under water as part of the agency's ocean-observing network
Royal Dutch Shell already has begun exploration activities in the Beaufort and Chukchi Seas, Clemente-Colon notes, with ConocoPhillips laying out its own exploration plans.
"They're going to go next," he says.
Research into operational ice and weather forecasting for the Arctic Ocean – part of a broader Arctic research effort guided by the federal Interagency Arctic Research Policy Committee – is moving along three broad tracks: building a long-term network of instrument packages moored, floating, or installed on autonomous undersea vehicles to measure the processes influencing the ocean, ice, and atmosphere; improving weather and ice-forecasting models and their ability to ingest information gathered by the far-flung sensors; and supporting field experiments that aim to answer focused questions on these key processes.
For instance, the Office of Naval Research is supporting two five-year research projects that deal with some of these issues.
Of particular interest is the so-called marginal-ice zone, a region of broken, mobile ice floes that surrounds the older, thicker ice pack. That zone changes from melt season to melt season. As the zone retreats at the start of the season, it exposes more ocean. This increases the distances wind-driven waves and swells can travel.
"That opens up new possibilities for deterioration of the ice cover as you change floe size, ice-cover concentration," and the water and air temperatures," he says.
The topic is the centerpiece of a six- to seven-month field study the agency is underwriting for 2014 in the Beaufort Sea focused on setting out a range of high-tech instruments, including some on ice floes to track their evolution and motion.
In addition, researchers will specifically study the origins and behavior of waves and swells on the ocean as the ice pack shrinks, and the mechanics of ice break-up as the swells and waves erode the edges of the ice pack to form the marginal-ice zone.