TORONTO – Arctic sea ice coverage has fallen far below average for this time of year, leaving many wondering if summer sea ice will hit a new low.
The U.S. National Snow and Ice Data Center published data this week showing that the average sea ice extent for May was 580,000 square kilometers (224,000 square miles) smaller than in May 2004, the previous record low for the month. The average area hit 12 million square kilometers (4.63 million square miles).
On a day-to-day basis the sea ice extent is shrinking at a rate two to four weeks ahead of levels seen in 2012.
This graph shows Arctic sea ice extent as of June 6, 2016. (National Snow and Ice Data Center)
Arctic sea ice has received much attention in recent years because it is one of the key components of the climate system – and a measure of global warming.
Although there has been a lot of talk about whether the trend will continue and make this summer’s sea ice extent the lowest on record, it is still too early to know for sure.
“There is a lot of variability in the system, so you can always move off that trend,” said David Barber, an Arctic sea ice expert at the Centre for Earth Observation Science at the University of Manitoba, in Winnipeg. “But the probabilities are pretty high that it is going to be a light ice year.”
At a meeting of the European Geophysical Union in April, Marcel Nicolaus, a sea ice physicist at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, warned that the 2016 summer sea ice could equal or eclipse the record low of 2012.
The record-low sea ice extent comes on the heels of a year of record temperatures globally. April was the warmest month since global record-keeping began, and the 12th consecutive month of record-breaking temperatures, according to the U.S. National Oceanic and Atmospheric Administration (NOAA).
“There have been a lot of dramatic events going on in the Arctic this year,” said Barber. Warm air over the Arctic in December, the opening of the Arctic ice pack through the winter, storms and the strong El Niño have all weakened the sea ice. “This has been a year-long phenomenon,” he added.
So far, the area of sea ice covering the Arctic Ocean is more than 1 million square kilometers smaller than in May 2012. In that record year, the sea ice melt accelerated in June. It will take a cloudy and cold summer to keep a record-breaking year at bay.
Arctic sea ice plays several roles in the global climate system. Its bright white surface reflects some of the sun’s heat back into space and keeps the heat stored in the ocean out of the atmosphere. When it retreats in the summer months, the dark ocean water absorbs more heat. In the winter, when the Arctic is dark, open areas of water release heat from the ocean and this warms the atmosphere.
Not only is the sea ice area shrinking but it is also getting thinner. On average, it was 15cm (6in) thinner in May than it was the year before, according to the Polar Science Center at the University of Washington, in Seattle. But it was substantially thinner in some parts of the Arctic, including the Beaufort and Chukchi seas, and the Barents Sea, compared to 2012.
This map shows the difference in ice thickness for May 2016 relative to the 2000–15 base period. While sea ice is thinner overall, with particularly negative anomalies in the Beaufort and Barents seas, ice thickness is a bit thicker in the East Siberian Sea area. (Polar Science Center, University of Washington)
Researchers from the Danish Meteorological Institute raced to rescue a weather station from the ice near Qaanaaq, northwest Greenland, when the ice there broke up earlier than expected, Science Nordic reported.
Last month also saw a jump in atmospheric levels of the greenhouse gas, carbon dioxide. Data published by NOAA this week showed that the average monthly level for CO2 in May was 407.7 parts per million, the highest level ever recorded.
The red line shows the recent monthly mean values for carbon dioxide measured at Mauna Loa Observatory, Hawaii. The black line shows the trend over time. (Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration)
This is all happening as the Arctic ecosystem is beginning to awaken.
In spring, when the sunlight returns after many months away, light and nutrients – the two ingredients necessary to kick-start the Arctic marine food web – are in abundance. With thinner and less plentiful sea ice, under-ice phytoplankton are starting to grow earlier in the year when there are a lot of nutrients in the area.
“We are starting to see a lot stronger productivity right beneath the sea ice as it starts to melt,” said Barber. “These algae blooms and phytoplankton blooms tend to be stronger than they used to be, and I expect that to happen this year as well.”
Some Arctic animals might be able to take advantage of the early feast, but others, including migratory animals, may not arrive in time, creating a mismatch in supply and demand in the food web.