An iconic whale species will soon be aiding climate change research. Narwhals are spending more time near melting sea ice and researchers hope to exploit this new behaviour by tagging the mammals with temperature sensors to help us accurately monitor underwater sea ice melt for the first time.
Sea-level rise may be the greatest threat we face from global warming. One key factor in how much the water will rise is Greenland’s ice sheet, a frozen expanse that is 2400 kilometres long and up to 1100 kilometres across, and covers 80 per cent of this vast island.
But this ice sheet is not as frozen as it once was. Warming conditions are causing melting from above, which then speeds up melt below the surface, a one-two punch that accelerates overall glacier loss.
Eight per cent of the world’s fresh water is trapped in this ice sheet. As it thaws, sea levels rise, salinity drops and weather fluctuates, threatening billions of coastal dwellers around the world. Researchers estimate that sea levels would rise 7 metres if the entire ice sheet melted.
But it is hard to measure exactly how fast the ice from glaciers flowing off Greenland is melting underwater, which could give an indication of the ice sheet’s overall status.
The decline in Greenland’s ice is catastrophic for polar bears and seals, but some creatures, including narwhals, may be benefiting, and their relationship to this changing environment is providing insight on what is going on underwater – and maybe how to save the ice.
“It’s kind of like narwhals are oceanographers,” says Kristin Laidre, an ecologist at the University of Washington who says the whales could be fitted with sensors to turn them into the first tool to effectively measure underwater glacial melt.
When run-off from ice melt hits the sea and glaciers calve off icebergs, it stirs up the ocean ecological system and brings nutrients to the surface, increasing the food supply. The melt also influences how much warm water enters the Arctic. Laidre’s work tracking the unicorn-like narwhal has found that the mammal spends so much time in and around melting ice that it seems to be the species’ new preferred habitat.
Laidre hopes that tracking narwhals as they swim under the edge of the ice sheet will enable her to measure its temperature with sensors and use this to explain the changing melt. Until now, this has been difficult to accurately study. Collected data will be transmitted to polar-orbiting National Oceanic and Atmospheric Administration satellites as part of NASA’s Oceans Melting Greenland (OMG) project.
In 2010, Laidre used narwhals to measure temperatures in Canada’s Baffin Bay, a process she plans to replicate off Greenland to collect information from the front of the glacier.
“Based on narwhal locations, we can measure the temperature of fjords, how it varies and how it potentially impacts glaciers,” she says.
Laidre’s work with OMG will begin in summer 2018, and will focus solely on temperature. The project’s overarching goal is to study the changing glaciers and the entire ice sheet, and plan for what is arguably the gravest ecological challenge of this century.
To do that, OMG uses NASA’s G-III airplane to measure Greenland’s coastal glaciers and track their seasonal ebb and flow. Each summer, 250 expendable temperature and salinity probes will measure the volume and extent of warm, salty Atlantic water. These findings, along with airborne and ship-based observations of the sea floor, will be used to help predict global sea-level rise more accurately.
Animals including Antarctic seals and elephant seals off California’s coast have previously been tagged to provide information on the oceans. Depending on the size of the tag attached to marine creatures, researchers can collect temperature, salinity and depth data.
Journal reference: Biology Letters, DOI: 10.1098/rsbl.2016.0457
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