Climate change is putting the future of some seals at risk as icebergs on which they depend become smaller, and the movements of the ice in the oceans change.
Recent research in the Johns Hopkins Glacier and Inlet in Alaska has revealed how climate-driven changes are impacting the birthing season in seals.
Harbour seals depend on icebergs that break off from glaciers as an essential habitat, using these floating platforms for important activities including giving birth, caring for pups and moulting.
But as sea levels rise and waters warm, the number of icebergs and their shape and speed in water currents are all being impacted.
“Our work provides a direct link between a glacier’s advance and seals’ distribution and behaviour,” says author of the study Lynn Kaluzienski from the University of Alaska Southeast.
Kaluzienski presented the findings at the American Geophysical Union Annual Meeting in Washington, D.C, on Tuesday.
Seal home: johns hopkins glacier, glacier bay national park (unesco world heritage list, 1979), in alaska. (photo by deagostini/getty images)
Johns Hopkins Glacier, Glacier Bay National Park (UNESCO World Heritage List, 1979), Alaska. (Photo by DeAgostini/Getty Images)
The study looked into the John Hopkins Inlet and Glacier located in Glacier Bay National Park, Alaska.
The John Hopkins Glacier, in Glacier Bay National Park, is one of the only glaciers in the world that is growing thicker due to a wall of sediment, however most glaciers across the globe are melting.
Even if global temperatures only rise by 1.5°C, experts predict glaciers could lose up to one-third of their mass by 2100.
In higher temperature scenarios, such as 4°C+ warming, projections suggest over half of the world’s glaciers could disappear.
Fewer glaciers and icebergs mean fewer stable habitats for seals.
“We wanted to understand which of these areas seals were using and how this habitat is changing in response to advances at the glacier front and reduction in iceberg numbers,” says Kaluzienski.
“Icebergs are found throughout the fjord in regions of fast flow, within eddies, and close to the glacier.”
Kaluzienski and her team spent two years using aerial photography, time-lapse cameras and remote sensing data to document variations in seal distribution on the icebergs.
Seals typically come to the icebergs during June for pupping season and in August for moulting.
The glacier face of lamplugh glacier in johns hopkins inlet in glacier bay national park, southeast alaska, usa. (photo by wolfgang kaehler/lightrocket via getty images)
The glacier face of Lamplugh Glacier in Johns Hopkins Inlet in Glacier Bay National Park, Southeast Alaska, USA. (Photo by Wolfgang Kaehler/LightRocket via Getty Images)
The researchers say when the seals shed their fur they were more likely to be travelling on fast-moving icebergs in or close to the plume at the front of glaciers.
During pupping season mother harbour seals leave their pups on the ice platforms for extended periods while they hunt for food.
The researchers found that during pupping season, seals were on icebergs that were moving 20 centimetres per second slower than the moulting icebergs which suggests they might prefer slower and calmer seas to raise their pups safely.
The researchers advise that as the climate continues to warm, this might have impacts on the behaviour and distribution of these harbour seals.
In a 2020 paper, researchers found that ocean currents were speeding up because of climate change and that the energy of ocean currents increased by around 15% per decade from 1990 to 2013 which the team says might have implications for young vulnerable pups.
Faster currents may reduce the number of safe spaces these pups have to avoid predation during pupping season which could impact the population of seals.
“Interdisciplinary studies like this one coupled with long-term monitoring campaigns will be important to understand how climate change will influence tidewater glacier fjord ecosystems in the future,” says Kaluzienski.
Melting glaciers change seals’ habitats