In the words of the Bob Dylan song, the times they are a-changin’. The Arctic is warming four times faster than the global average and in Svalbard, average air temperatures have increased about 3°C over the past 30 years. What is causing these changes and what changes will they cause in turn?
By: Pedro Duarte, Haakon Hop, Philipp Assmy, Anette Wold, Allison Bailey, Heidi Ahonen, Marie-Anne Blanchet, Dmitry V Divine, Kit M Kovacs, Christian Lydersen, Geir Moholdt and Geir W Gabrielsen // Norwegian Polar Institute
Francesco De Rovere // National Research Council, Institute of Polar Sciences, Bologna, Italy
The Svalbard archipelago is a regional hotspot for global warming, which is causing dramatic changes across the archipelago, especially in the fjords along the west coast of Spitsbergen. Global warming (along with Arctic amplification) and Atlantification are the primary forces behind the declines in sea ice and retreat of glaciers, which in turn alter the ecosystems and their biodiversity. In addition, increasing human activity in the Arctic is causing a new array of impacts on ecosystems.
Changing cryosphere
Increasing air temperatures and milder winters, especially when combined with the presence of warm Atlantic Water, are causing dramatic changes in fjords. These include sea ice declines, retreat of tidewater glaciers (those that terminate at sea) and increased freshwater flows and sedimentation from melting glaciers and thawing permafrost.
Atlantification
Atlantification refers to the increasing influence of Atlantic Water in the Arctic. The Svalbard Archipelago is surrounded by contrasting water masses, creating a “battleground” of ocean fronts between the cold Arctic Water masses and the relatively warm Atlantic Water. Fjords along the west coast of Spitsbergen are particularly susceptible to the warming influence of Atlantic Water because the West Spitsbergen Current flows northward along this coast and exchanges water with the fjords, making them warmer than those located elsewhere around the archipelago. The continuous “war” between water masses driven by large-scale circumpolar pressure patterns determines colder or warmer periods in Svalbard fjords. However, superimposed on these “battles”, global warming continues unabated, and it is expected to continue to affect fjords and glaciers throughout Svalbard in years to come.
In summer, melting glaciers generate freshwater run-off to the fjords. Over recent decades, these influxes have intensified, promoting outflow of brackish water at the surface towards the ocean and inflow of shelf water towards the fjord at intermediate and bottom depths.
Winds blowing along the north-south direction have grown stronger. The combined effects of wind and the Earth’s rotation lead to transport of water perpendicular to the direction of the wind. When such winds blow along the west coast of Spitsbergen, these processes force Atlantic Water into west-facing fjords like Kongsfjorden.
Changing biodiversity
The reduction of sea ice decreases the quality and availability of habitat for iconic Arctic species (e.g. polar bears, bearded and ringed seals, white whales and ivory gulls). Additionally, the retreat of tidewater glaciers has implications for fjord ecosystems through expansion of fjord arms, increased turbidity and changed water circulation and nutrient delivery patterns. In the absence of sea ice, tidewater glacier fronts are climate refugia for Arctic fishes and invertebrates that serve as prey for seabirds and marine mammals. Glacial ice in the form of icebergs also functions as resting platforms for seals when annually formed land-fast sea ice is not available. However, as tidewater glaciers retreat onto land, these habitats will disappear, negatively affecting many Arctic endemic species. Reduction in sea ice has also resulted in increased vessel traffic and tourism, adding a new array of stressors to fjord ecosystems such as plastic litter, chemical pollution and noise.
Atlantic Water brings a multitude of lower-latitude species to the Arctic. This process, termed borealisation, has implications for local food webs and biodiversity. With the addition of boreal species on top of resident Arctic ones, the biodiversity increases even if the abundance of Arctic species is reduced.
Increased noise pollution
Svalbard fjords are exposed to increased maritime activity leading to concerns about the effects of underwater noise on local marine fauna. Over the past decade, ship traffic has increased in Kongsfjorden with recreational and passenger vessels driving most of this trend. Noise levels have become higher, especially in the summer and autumn due to both natural physical processes (ice melt and storms) and human activities.
Perspectives
Some of the drivers of change affecting the Arctic act globally and provoke a cascade of effects all the way down to coastal regions and fjords. Others act regionally, reinforcing the effects of global drivers. We must improve our understanding of the effects of these drivers to pursue one of the goals of Norway, which is to make Svalbard one of the best managed wilderness areas of the world. Large-scale mitigation depends on international agreements and concerted actions given the wide geographic scope of climate change drivers. However, local actions can help reduce cumulative pressures on ecosystems. Svalbard and its fjords may be seen as harbingers of change and sentinels regarding the effects of ongoing global warming.
