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Dramatic regime shift observed in Arctic marine ecosystems

A new study led by the Greenland Institute of National Resources has found that a sub-arctic ecosystem off Southeast Greenland, which has previously been dominated by large amounts of drifting pack ice, has changed during this century to a more temperate system with higher ocean temperatures and less sea ice. According to the experts, changes in summer ocean conditions are currently making this region more attractive for marine species such as fin and humpback whales, as well as other new species.

The driver of such massive ecological changes, or regime shifts, are known in the scientific literature as tipping points, which may be irreversible and have cascading effects throughout various ecosystems.

“In this case, the new regime will likely become permanent for the foreseeable future, unless temperatures cool and the ice export from the north increases again. According to recent IPCC reports, continued 21st century climate change will make this scenario unlikely,” said study author Mads Peter Heide-Jørgensen, a marine biologist at the Greenland Institute.

“One of the main findings is that this event is so unusual in the past 200 years of summer ice observations in the region. We have seen big changes in some of the upper trophic levels. There are likely many other changes in the ecosystem and food web that have not yet been described and might be part of the reason why highly migratory species are coming to the region,” added Brian MacKenzie, an oceanographer at the National Institute of Aquatic Resources.

These shifts in the sub-Arctic have already started to occur since 2012, when, for the first time, bluefin tunas were accidentally caught in a trawl fishery in waters off East Greenland. Afterwards, unexpectedly large numbers of fin and humpback whales were found in the previously ice-packed waters of East Greenland, along with temperate species such as dolphins, killer whales, and pilot whales. At the same time, high Arctic marine species like narwhals and walruses, were dwindling in Southeast Greenland.

This ecological shift in the dominating regime in East Greenland was triggered by the decline in summer drift ice – particularly after 2000 – which opened the region to large predators that depend on open water for air breathing.

“The recent disappearance of summer pack ice along East Greenland demonstrates how meteorological perturbations are connected to changes in marine ecological conditions over distances several thousand kilometers apart,” Heide-Jørgensen concluded.

The study is published in the journal Global Change Biology

By Andrei Ionescu, Staff Writer

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