Scientists have found large numbers of fin and humpback whales in previously ice infested waters in Greenland. This indicates that the changes in this Arctic ecosystem are likely permanent.
The sub-Arctic ecosystem off the coast of Southeast Greenland, once dominated by large amounts of drifting pack ice, has changed during this century to a more temperate system with less sea ice and warmer ocean temperatures. These changes in summer ocean conditions are making the region more attractive for large numbers of fin and humpback whales, along with other new species.
Dramatic ecological changes such as these are considered regime shifts in the ecological literature. Shifts from one regime to another occur at a tipping point and may be irreversible. The regime shift has cascading effects throughout the Arctic ecosystem.
The study, titled ‘A regime shift in the Southeast Greenland marine ecosystem,’ was published in the journal Global Change Biology.
A sharp drop in temperature is unlikely
“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 makes this scenario unlikely,” explained Professor Mads Peter Heide-Jørgensen, from the Greenland Institute of Natural Resources.
“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 Arctic 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 Professor Brian MacKenzie, of the National Institute of Aquatic Resources at the Technical University of Denmark.
‘Tipping points’ of melting sea ice
The driver of the shift is known as a tipping element and the extent of drifting sea ice is an easily detectable tipping element, nowadays including satellite imagery.
In 2012, for the first time, bluefin tunas were caught as bycatch in a trawl fishery in waters off East Greenland. This indicated that something dramatic had happened to the Arctic ecosystem.
Furthermore, more evidence of ecological changes was mounting like the unexpectedly large numbers of fin and humpback whales that were found in the previously ice infested waters of East Greenland. They started to occur together with temperate species like dolphins, killer whales, and pilot whales. At the same time, observations of high Arctic species, like narwhals and walruses, were dwindling in Southeast Greenland.
Declining summer drift
This ecological shift in the dominating regime of East Greenland was driven by the decline in summer drift ice. A 200-year-long record revealed that unprecedented low levels of coastal sea ice were reached after 2000. This opened the area to the 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 Arctic ecological conditions over distances several thousand kilometres apart,” concluded Professor Heide-Jørgensen.
