A sea of change: Europe’s future in the Atlantic realm

Foreword

However cold it may seem to some of us in a Scandinavian winter, northern Europe enjoys a relatively mild regional climate for our latitude, thanks to the massive amounts of heat brought up from the subtropics by circulation patterns in the North Atlantic Ocean. So it is no surprise that suggestions that this heat transport may weaken or ‘switch off’ attracts much media attention, with headlines that may refer to ‘tipping points’ or ‘collapse’ of the overturning circulation that brings warm surface waters all the way to the Arctic Circle. Studies of the ocean climate on long timescales have found these processes to have stopped or seriously reduced, generally following large freshwater discharges caused by rapid melting of glacial or multi-year ice in the Arctic. Were this to happen, there could be the paradox that global warming can lead to a colder climate for some of us!

With Greenland and Arctic ice melting at a rapid rate owing to the current rates of global warming, and the evidence from past climates, the future of the Atlantic conveyer has become an important topic for research programmes, and scientific papers are step-by-step improving our understanding of the underlying processes and current trends. The overturning circulation that includes the influx of waters from the subtropics to as far as the Arctic is reported to be weakening, but there is not yet a consensus on trends. At the same time, sea levels are rising and seawater acidification continues, placing additional stresses and uncertainties in safeguarding Europe’s seas and coasts and the resources and ecosystem services that they provide. Europe is also looking to the seas to provide new resources, particularly renewable energy but also a range of activities under the general label of the Blue Economy.

In this report, we describe the underlying processes and trends in the Atlantic, and the ways in which the state of the ocean – currents, winds, waves and ocean mixing – impact Europe’s climate, marine environment and resources. The report looks at the implications for a wide range of European policy issues, from the future of our regional climate, through marine resource and energy, to fisheries management. As found in many environmental issues, there are important interactions between different areas of policy, and we hope this analysis will help to ensure synergy between economic and environmental approaches to marine policy.

Summary

Globally, the importance of managing the oceans in a more sustainable manner has been widely recognised in the United Nations Sustainable Development Goals (UN SDGs), the UN Decade of Ocean Science for Sustainable Development and elsewhere. In Europe the increased recognition of the importance of our oceans and seas is seen in the Blue Economy and in the Green Deal initiatives. However, such policies have to be set against the background that the historical state of flux in our oceans and seas is changing owing to global warming. This report focuses on the Europe’s future in the Atlantic realm and thus the Atlantic Ocean and the seas along Europe’s western coasts (excluding the Mediterranean and Black Seas).

Against the background of natural variability, direct impacts of global climate change can be seen in the sea surface temperature which has increased by nearly 1 °C since the 1890s, in sea level which has risen by 11–16 cm during the 20th century; and in seawater pH which has decreased by about 0.1 pH units since the start of the Industrial Revolution. Climate change may also be affecting the complex oceanic processes underpinning the goods and benefits we receive from marine ecosystems.

The acidification of Europe’s oceans and seas is increasing as atmospheric and therefore seawater concentrations of carbon dioxide (CO2) rise. However, changes in circulation, especially those that promote upwelling of deeper waters, can exacerbate these trends through increasing microbial decay of organic matter. The variation in pH in some European waters may approach 1 between seasons and the resilience of commercially important species (particularly in their early life stages) to such variations remains poorly understood. While observations of carbon cycle and ocean acidification are ramping up within the Integrated Carbon Observation System, observations from key regions are missing and, combined with limited data on the impacts on marine ecosystems and commercial fisheries, information to assess the associated risks of acidification is lacking.

Europeans Academies Science Advisory Council, 2021. A sea of change: Europe’s future in the Atlantic realm. EASAC policy report 42. Report.

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