Arctic Marine Ecosystems Still Under Pressure

The Arctic is particularly hard hit by climate change. Here, due to “Arctic amplification”, temperatures are rising at more than twice the global average rate. As a result, marine ecosystems in the High North are under tremendous pressure and the impacts at various levels have been visible for years. For example, organisms’ distribution ranges, growth, metabolism and behaviour have changed, reshaping entire food webs.

In 2011, a team led by Paul Wassmann from the University of Tromsø published the first comprehensive assessment of climate change impacts on Arctic marine ecosystems. Now Sören Brandt from Kiel University and Paul Wassmann and Dieter Piepenburg from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, have presented an extensive update.

“Climate change has left behind a range of clearly visible ‘footprints’ in the marine ecosystems of the Arctic,” explains Sören Brandt. “We analysed related scientific publications from the past 10 years and found reports on no less than 98 of these footprints. We concluded that the majority of the effects reported in 2011 have since been confirmed and therefore have to be considered ongoing trends.”

Especially the shifting of distribution ranges to the north can be seen in numerous species, particularly among fish. Species from more temperate latitudes like the Atlantic cod and shellfish are following the rising water temperatures and increasingly spreading to Arctic waters – where they are displacing more and more native Arctic species, forcing them to move their habitats farther north. Similar effects can be seen in starfish, bivalves, crustaceans, seabirds and whales. “Because subarctic and boreal species are migrating from the south, the biodiversity in the Arctic seas will very likely increase at first,” says Dieter Piepenburg, who was also one of the main authors of the chapter on the polar regions in the IPCC Assessment Report on climate change impacts released in 2022. “But in the long term, the Arctic could be headed for a turning point, and therefore to a decline in biodiversity. At some point, the warming and acidification produced by rising CO₂ concentrations in the water will exceed native species’ physiological adaptability. Since they’ll no longer be able to retreat farther north, they could even disappear completely.”

A further trend is the increased primary production in Arctic waters. As the sea ice dwindles, the areas of open water are growing. Here, phytoplankton can grow more intensively and longer. As a result, they produce more biomass, which affects the entire food chain and leads to measurably improved health in e.g. bowhead whales. These domino-like cascade effects (referred to as secondary footprints), which weren’t explicitly considered in the 2011 survey, clearly show how far-reaching the effects of climate change are in the Arctic. “Despite these partially positive effects of climate change, it’s readily apparent that a massive transformation is underway in the Arctic seas, one that will most likely accelerate in the future,” says Dieter Piepenburg. “And in the long term, those Arctic species most adapted to the cold will definitely come out on the losing end.”