Key oceanic and polar processes driving regional & global climate change

The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the Earth climate. It can significantly imprint the vertical structure of global ocean heat uptake and drives a large part of the deep-ocean oxygenation and deep storage of anthropogenic carbon. The AMOC is expected to slow down with climate change with strong impact on the oceanic heat storage, carbon pump, and ventilation. Such change in the AMOC is also expected to impact the polar regions that are already experiencing warming at a faster rate than other places. Indeed, the current climate in polar regions is influenced by interactions between the ice sheets, the ocean, sea ice and atmosphere, and their response to anthropogenic climate forcing. Both the Arctic and Antarctic are connected to global climate through several feedback mechanisms, such as the AMOC, snow albedo effect, sea level rise from melting glaciers and ice sheets, changing terrestrial ecosystems that lead to changes in fluxes of carbon dioxide, and methane nutrients. Several of these processes exhibit tipping points (e.g. methane hydrate release in a warming Arctic Ocean, thawing permafrost and release of carbon). Potential tipping points in the polar regions include a significant slowdown of the AMOC and a destabilization of Greenland and Antarctica ice sheets. There is deep uncertainty regarding the contribution the melting of the Antarctic ice sheet will make to mean global sea level rise towards the end of this century. The potential consequences vary greatly from region to region making the information needed at local and regional level highly relevant for supporting local and regional adaptation decisions. The Southern Ocean controls the natural release of CO₂ from the ocean, helps to absorb anthropogenic CO₂ and modulates transport of heat towards the Antarctic ice cap. The largest anthropogenic storage of CO₂ is in the North Atlantic. The observational record is not long enough to determine if changes observed in the circulation of the Atlantic and Southern Oceans are due to natural variability, or are a response to anthropogenic forcing.

Actions should aim at developing innovative approaches to address only one of the following options:

1. Regional & global components of the Atlantic meridional overturning circulation (AMOC)

Actions should further the research on how and why the AMOC has changed over time, and how it will evolve in the future. Actions should endeavour to understand the entire system of the AMOC, as well as its links with the world ocean circulation system, in particular with the polar oceans. Actions should enable the sustained and sustainable observation of the AMOC by improving, developing and/or deploying existing and novel methods and technologies to observe the AMOC and its functions in the Earth system, and may include the development of advanced methods and digital technologies such as machine learning algorithms and multiple observational constraints. Observations should address climate change indicators, including indicators of past climate change, measurements of ocean heat content and currents, carbon dioxide solubility and fluxes, modifications of ocean circulation and climate feedbacks.

Action should address observational gaps of existing AMOC observing systems, focusing for example on formation regions, ocean boundaries and topographic constriction points, which are not or only poorly observed by large-scale observation systems such as the Argo array of profiling floats, or current generation satellite altimeters. Emerging technologies such as ocean gliders, remote mooring telemetry and autonomous vehicles offer opportunities to streamline traditional transport mooring arrays. This will lead to a more precise assessment (key for e.g. IPCC reports) of the risk of rapid changes using the newly released CMIP6 database and high-resolution models developed, inter alia, within the EU Horizon 2020 framework programme. Actions should add new observations of biogeochemical parameters (including carbon) and ecosystem-relevant quantities to observing arrays, thus providing synergy and optimisation of the long-term research infrastructure. Actions should also include reconstructions of deep boundary current intensities at different time scales to better discriminate/characterise anthropogenic impact from natural variability during the observational period. Actions should focus on improving models to better understand short-term variability and impacts on European and global climate. Moreover, action should interpret the recent changes in this context, to understand how close we may be to a climate tipping point.

1. Improving understanding and observation of Antarctic key processes and the Southern Ocean circulation

Actions should endeavour to reduce the deep uncertainty regarding the Antarctic contribution to global mean sea level rise towards the end of this century. Action should further the science and understanding of the dynamics of the Antarctic ice sheet and its climatic triggers, which constitute the major source of uncertainty about sea level rise. Actions should endeavour to understand the sensitivity of the low-latitudinal oceans to freshwater fluxes in order to advance the comprehension of the dynamics and functioning of the southern sources of deep waters, the Antarctic bottom water (AABW) circulation and thus counteract the deficit of scientific knowledge limiting the complete understanding of decadal to millennial time-scale climate change. Actions should focus on the potential importance of feedbacks between the northern and southern sources of deep waters. Actions should endeavour to close the gap towards producing an integrated view of the planet's climate system and the role of Antarctica in it. Actions should focus on understanding the Antarctica climate variability, Antarctic surface mass balance and the forces that control future change and responses to change, including tipping points. Actions should research the Antarctic ice sheet dynamics and integrate this knowledge into coupled ice sheet-climate models adapted to the Antarctic and Southern Ocean region, in order constrain and improve the accuracy and precision of predictions of future changes in global and regional temperatures, ocean acidification and sea level rise. Actions should reduce the gap in ocean observations in the Antarctica allowing for improved sea ice and weather forecasting and other environmental predictions that could improve the quality of various applications including search and rescue, coupling with numerical weather and seasonal predictions, historical reconstructions (reanalysis), aquaculture and environmental management including environmental emergency response. Actions should endeavour to understand how ice-shelf loss in Antarctica link with and impact on the ocean’s circulations system, in particular the AMOC, and the relationship between the relative strength of the Antarctic circumpolar current (ACC) and AMOC.

For both options, international cooperation is strongly encouraged, with a strong linkage with the ongoing activities under the All-Atlantic Ocean Research Alliance, with participation from bordering countries and countries – beyond the EU Member States and countries associated to Horizon Europe – that took part in the Arctic Science Ministerial. Actions under this topic should plan on a close collaboration among each other and with the EU Polar Cluster. Actions should build upon and link with past Horizon 2020 projects, EU PolarNET2, Copernicus, Sustaining Arctic Observing Networks (SAON), Scientific Committee on Antarctic Research (SCAR) and Southern Ocean Observing System (SOOS), and other international Ocean Observing Initiatives. The R&I needs to be conducted in a multidisciplinary and ecosystem-based approach. All in-situ data collected through actions funded from this call should follow INSPIRE principles and be made available through open access repositories supported by the European Commission (Copernicus, GEOSS, and EMODnet).

This topic links with research conducted under Cluster 5 (‘Climate, Energy and Mobility’) Destination ‘Climate sciences and responses’ and Cluster 6 (‘Food, Bioeconomy, Natural Resources, Agriculture and Environment’) Destination ‘Land, ocean and water for climate action’ and Destination ‘Innovative governance, environmental observations and digital solutions in support of the European Green Deal’, Deploying and adding value to Environmental Observations.