Trapped in the ice

This study is one I have wanted to write about for a while but kept postponing. The research is important, but the events bug me, because it includes many whales dying. That is one spoiler alert. The other hindrance is that this article stands to upset global warming skeptics.

For some comic relief, watch the YouTube video with a selection from “Finding Nemo” when Dory speaks Whale. Even if it anthropomorphizes the relationship between fish and marine mammals. This clip is also nice about freeing a trapped and drowning whale.

Now, to the narwhals of the Arctic, nicknamed unicorns of the sea. They are related to orcas and bottlenose dolphins and live near Greenland and Canada. Check out narwhals here.. There is audio on the page, too, so you can hear what they sound like. They probably sound different when in distress, but I don’t speak whale or narwhal. It is distressing for them when the weather suddenly turns frostier than frosty and ice develops where a passage normally is. Those conditions create ice entrapments, like ponds with icy shores all around. These entrapments are deadly for narwhals.

According to the University of Washington’s polar science center blog, the Artic is subject to many changes due to marine shipping and sea ice changes, to name just a few factors. Studying narwhals is a way to understand the animals and the ongoing shifts in this region.

Glenn Williams, NIST via Wikimedia Commons

Swimming in the Arctic, there is often more ice than water around narwhals. But sometimes they get surrounded by a big solid block of ice. Swimming means drowning because the animals would not be able to come up for air. After all, they are mammals. If they stay, they can breathe but they starve. It is the animal version of no-win situation.

Entrapment events tend to be reported in the winter, particularly February and March, and are often observed by Inuit hunters. If the situation is deemed hopeless for the animals, the narwhals are harvested. But not all entrapments are recorded, so their frequency is unknown.

Science writer Todd McLeish points out that ice entrapments, called savssats by the Inuit, are probably happening much more frequently than records suggest. Witnesses and observers are just not always around, since the Arctic is thinly populated.

Scientists studied entrapments between 2008 and 2010 in the ocean area off the coasts of Greenland and Canada. They found an unusual pattern as they looked at four such events near the areas where the whales summer. It turns out that the narwhals had, for some reason, delayed their departure from these areas into the late fall and winter. That delay turned into a deadly situation for them.

It appears there might be a link to different weather conditions: the normal autumn freeze-up happened later in each of these entrapment locations, sending the narwhals different cues about moving on to other waters, report Kristin Laidre and Harry Stern of the University of Washington, and colleagues Mads Peter Heide-Jørgensen from the Greenland Institute of Natural Resources, and Pierre Richard from Fisheries and Oceans Canada who collaborated on this work. Their paper was published in the journal Polar Biology.

The team points out that around 80,000 narwhals live in Baffin Bay between Greenland and Canada and around 7,000 of them call the Greenland Sea home. In the fall, when ice quickly forms, the animals move away from the coast toward open water, and then return in the spring as the seasons change.

Three of the locations where entrapments occurred had no wind and cold temperatures. Wind is crucial for creating new patches of open water. In these no-wind and cold conditions, the narwhals were limited to areas where ice grows rapidly. Although they can break ice, three days of -19 degrees centigrade leads to ice layers beyond their limits as marine mammal icebreakers.

The researchers also studied the sea ice pattern changes in six of the narwhal’s summering spots and fit the four entrapment events in with all of the other ones that have been reported between 1912 and 2010.

The scientists report that in mid-February of 2008, hunters discovered 30-40 narwhals off of East Greenland at Amanga Island. “All entrapped whales were taken in a subsistence harvest,” they write. In November of that year, several hundred narwhals were found off the coast of Canada, near Pond Inlet. Open water was 50 kilometers away. Determining that, “the animals had no chance of escaping to open water,” a total of 629 whales were killed. One year later, around 50 to 100 narwhals got trapped off the coast of West Greenland, near Qaanaaq, and 38 animals were harvested. In February 2010, 30 to 100 whales were entrapped off the coast of West Greenland. They were swimming between three and 4 four large ice floes about two kilometers wide. The nearest open water was between 30 and 40 km away. “During the subsistence hunt on February 6, approximately 35 whales were secured and more lost under the ice,” according to the study authors.

Blogger McLeish writes about Laidre’s work of examining the distribution and timing of known ice entrapments and looking at the trends in the breakup of sea ice on the narwhal’s summering grounds. The ice seems to be forming later. “Over a 30-year period there is a three to four week difference in when the ice forms,” she told McLeish. “If ice formation is a clue to the narwhals that it’s time to get out of their summering grounds, then the trigger is changing, the pattern is changing.”

It might seem easy to jump to the conclusion that changes in the timing of ice formation makes narwhals more vulnerable to ice entrapments and that the team has found an implication of global warming. While that may be the case, there are “precious little data from which to draw conclusions just yet,” he writes of Laidre’s work.

As Laidre and her colleagues write in their paper, it is not clear whether the four entrapments are due to random variation or “whether there is an actual trend in prolonged summer residence time as narwhals adapt to a longer open water season.”

Climate models suggest increased variability in climate extremes and more frequent and intense weather events. But rapid changes in weather and ice conditions do not appear to always lead narwhals to move into open water areas, so the scientists recommend “careful documentation” of future entrapments to assess the relationship between the changes in autumn freeze-up and narwhal vulnerability.

Links:
Kristin Laidre et al. Unusual narwhal sea ice entrapments and delayed autumn freeze-up trends. Polar Biology (2012) 35:149–154 DOI 10.1007/s00300-011-1036-8


The University of Washington Polar Science Center Blog

Image:
by Glenn Williams, National Institute of Standards and Technology. Public domain image, via Wikimedia Commons

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Posted on April 18, 2012, in Animals, Arctic Ocean, marine mammals and tagged , . Bookmark the permalink. Leave a comment.

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