Arctic snowfall accumulation plays a critical role in ringed seal breeding, but may be at risk due to climate change, according to a new study in Geophysical Research Letters. Sea ice, which is disappearing at an alarming rate, provides a crucial platform for the deep snow seals need to reproduce.
Ringed seals (Phoca hispida) require snow depths of at least 20 centimeters (8 inches): deep enough to form drifts that seals use as birth chambers.
Ringed seals rear their young in April, which also makes the timing of adequate snow depths critical.
“Depending on how fast greenhouse gases increase this century, the area of Arctic sea ice with at least 20 centimeters of snow in April could decrease by nearly 70 percent,” co-author Cecilia Bitz, associate professor of atmospheric sciences at the University of Washington, told mongabay.com.
Ringed seal (Phoca hispida). Photo by: NOAA.
Sea ice reduction through autumn could be particularly perilous to future seal populations.
“Cumulative snowfall changes little from September to April during the 21st century in climate model projections. However, the projected loss of sea ice in autumn causes early season snowfall to fall into the ocean,” said Bitz, adding “it is the loss of the sea ice platform to catch the snowfall that causes snow depths to decrease in the future”.
Ringed seals are unable to build caves deep enough if insufficient snow is available. In fact, scientists have found that seal pup survival diminishes in locations without at least 20 centimeters of snow on level sea ice in April, increasing pup mortality through exposure (and the threat of freezing) and predation.
Seal caves may be threatened by other features of climate change too. For example, warmer temperatures mean that caves could melt sooner, affecting the time needed for pups to mature.
Increased precipitation as rain is another factor according to Bitz.
Ringed seal pup. Photo by: NOAA.
“Rainfall rates will roughly double by the end of the 21st century and rain falling on snow caves can cause them to collapse,” she notes, adding that “rain falling on sea ice can also accelerate snow and ice melt rates. Higher rates of rainfall are a further pressure on seal habitat”.
The findings could also have major implications for other Arctic species that depend on ringed seal populations.
“Ringed and bearded seals are the most common food for polar bears. They are adept at hunting seals, and seals have enough fat to satisfy their energy needs,” says Bitz.
Scientists have long recognized that climate change imperils Arctic species such as polar bears (Ursus maritimus), Arctic foxes (Alopex lagopus), killer whales (Orcinus orca) and even glaucous gulls (Larus hyperboreus). Now, their existence could be challenged further, by the potential plight of an important prey species.
A decline in ringed seals would also hurt another top predator: humans. Ringed seals are extremely important for the Arctic’s indigenous human populations. Widely hunted across Arctic regions, ringed seal meat is central to many indigenous diets while their skins are used for warm clothing in the frigid climate.
Ringed seal hides have been used by indigenous people for millennia as clothing. Photo by: Mickey Bohnacker.
Not only are ringed seals prized for the practical benefits they deliver, they are also culturally and socially significant for indigenous populations across the expanse of the Arctic.
Ringed seals are currently listed as Least Concern by the IUCN. In 2010, the National Oceanic and Atmospheric Administration (NOAA) proposed (together with growing evidence) that both ringed and bearded seals be listed as ‘Threatened’ under the Endangered Species Act (ESA); however the decision is still under consideration.
(10/29/2012) Twelve miles off shore from the Arctic National Wildlife Refuge floats a seemingly tiny man-made device—at least from an airplane—but it’s actually a 160-foot high Shell Dutch Royal oil drilling rig. While the hugely controversial plan to drill for oil in the Arctic ocean was postponed this year due to a variety of mishaps and delays, the Shell rig is expected to be in the area until the end of month drilling top holes in the ocean floor to prep oil drilling next year.
(09/19/2012) Some twenty days after breaking the record for the lowest sea ice extent, the Arctic sea ice has hit a new rock bottom and finally begun its seasonal recovery. In the end, the Arctic sea ice extent fell to just 3.4 million square kilometers (1.32 million square miles) when only a few months ago scientists were wondering if it would break the 4 million square kilometers. The speed of the sea ice decline due to climate change has outpaced all the computer models, overrun all expert predictions, and shocked even the gloomiest scientists.
(08/27/2012) One of the most visible impacts of climate change—melting summer sea ice in the Arctic—just hit a new milestone. Scientists with the U.S. National Snow and Ice Data Center (NSIDC) have declared that this year’s Arctic sea ice extent dipped below the previous record set in 2007 as of yesterday. The record is even more notable, however, as it occurred more than a fortnight before the Arctic’s usual ice melt season ends, meaning the old record will likely not just be supplanted, but shattered.
(06/06/2012) If melting sea ice and glaciers weren’t enough, now climate change is producing what researchers call a “structurally novel ecosystem” in the northwestern Eurasian tundra. Warmer weather and precipitation changes in the region, which covers western Russia into Finland, has allowed shrubs of willow and alder to grow into sparse forests within just forty years, according to a new study in Nature Climate Change. The new ecosystem could have global implications as researchers say it is likely to worsen global warming due to a decline in the region’s albedo, i.e. the sunlight reflected back into the atmosphere due to snow cover.
(05/03/2012) Polar bears (Ursus maritimus) are capable of swimming incredible distances, according to a new study published in Zoology, which recorded polar bears regularly swimming over 30 miles (48 kilometers) and, in one case, as far as 220 miles (354 kilometers). The researchers believe the ability of polar bears to tackle such long-distance swims may help them survive as seasonal sea ice vanishes due to climate change.
(02/13/2012) Last year the Arctic, which is warming faster than anywhere else on Earth due to global climate change, experienced its warmest twelve months yet. According to recent data by NASA, average Arctic temperatures in 2011 were 2.28 degrees Celsius (4.1 degrees Fahrenheit) above those recorded from 1951-1980. As the Arctic warms, imperiling its biodiversity and indigenous people, researchers are increasingly concerned that the region will hit climatic tipping points that could severely impact the rest of the world. A recent commentary in Nature Climate Change highlighted a number of tipping points that keep scientists awake at night.
(02/09/2012) Drilling in the Arctic waters of the U.S. may become as contested an issue as the Keystone Pipeline XL in up-coming months. Scientists, congress members, and ordinary Americans have all come out in large numbers against the Obama Administration’s leases for exploratory drilling in the Beaufort Sea and the Chuckchi Sea.
(01/24/2012) Threats to marine mammals usually include climate change, drowning as by-catch, pollution, depletion of prey, but what about eating marine mammals? A new study in Biological Conservation finds that a surprising 87 marine mammals—including polar bears, small whales, and dolphins—have been eaten as food since 1990 in at least 114 countries.