The present-day Arctic is in fast transition. In particular, the atmosphere and ocean are warming, and the cryosphere is retreating. Such a regime shift in the Arctic can have immediate and profound impacts on the marine ecosystems and fisheries and hence on society. What happens in the Arctic does not stay in the Arctic. Changes in the Arctic sea-ice and freshwater content have far-field consequences that can modify European climate and warm the Southern Ocean - potentially leading to accelerated loss of Antarctic sea/land ice.
The Antarctic, long considered to be buffered from the effects of climate change by the Southern Ocean, is observed to suffer from thinning of ice shelves in multiple sites induced by the ocean warming underneath. The weakened buttressing effect of ice shelves is contributing an increasing share to the global mean sea level rise, disproportionately affecting Europe.
The rapid changes that are underway in the Arctic and part of Antarctica urge a thorough assessment of the key ocean and climate processes, as well as how they may fundamentally change in a warming future. Climate models are instrumental in understanding the polar climate, but large uncertainties remain due to unresolved key processes in both the regional and global context.
The main goal of KeyPOCP is to improve our understanding of how ocean and climate dynamics in the polar regions and the global context depend on small-scale processes (e.g. circumpolar currents, shelf-basin exchange) that are currently unresolved in most modern climate models. To achieve this, we have utilised a new ensemble of high-resolution CESM simulations, and we have worked on a high-resolution configuration of the Norwegian Earth System Model, NorESM. This new configuration shows promising improvements in some areas of the polar oceans, but challenges remain, particularly in
the dynamically complex Southern Ocean. To complement these highly complex simulations, and to understand the processes observed in these complex Earth system models, we have also used idealised numerical experiments to gain a mechanistic understanding of high-latitude ocean processes and their role in the global ocean. This work led to an increased understanding of the role of high-latitude ocean convection and its importance for the global overturning circulation.
To increase our understanding of the role of small-scale processes along the Antarctic continental shelf, we have used a combination of advanced field observations and numerical modelling to increase our understanding of the dynamics of the Antarctic Slope Current in the Weddell Sea, which is an important barrier that controls how much heat reaches the ice shelves in the Weddell Sea. In particular, we focused on the role of seasonality and wind in these processes.
KeyPOCP made a potentially long-lasting impact on the China-Norway collaboration on polar research by bringing together several leading climate modelling groups and one leading observational group, pushing our abilities in high-resolution modelling of polar oceans and climate. In August 2024, the PI of KeyPOCP, together with the PIs of other Chinese-Norwegian Collaboration Projects within Climate Systems, organized a joint workshop for all of these collaborative projects to expand this collaboration beyond just members of KeyPOCP, and ensure continuing joint work on polar climate science beyond the duration of this project.
The experience of the Chinese partners in the high-resolution global configurations of the climate model (CESM-HR) helped the development of a high-resolution configuration of the Norwegian Earth System Model, NorESM-MX. While challenges with this high-resolution model configuration still exist, due to both the complexity of such models and the required resources (CPU, storage, human), KeyPOCP certainly led to an enhanced understanding and experience in the local climate modelling community on how to deal with such complex modelling challenges. In addition, the findings of this project will guide the development of the lower resolution model configurations that will remain important for many applications in the future as well.
The scientific results of KeyPOCP add another piece to the puzzle of understanding high-latitude ocean processes, such as deepwater formation or coastal processes, and the role they play in our current and future climate. In the long term, these scientific results will have an impact on Arctic policies as the processes studied in KeyPOCP are important for the marine ecosystems, fisheries, tourism, and shipping in the polar regions as well as for the Antarctic ice sheet instability (a critical tipping point) and therefore for the global sea level rise.
Underlying the polar climate system is a number of closely coupled processes that are interconnected through complex feedbacks on a range of temporal and spatial scales. Understanding of these processes often relies on regional and global climate modelling as instrumental records are limited in these inaccessible and remote areas. The lack of observational constraints makes model evaluation and assessment of future climate change challenging, which is problematic as the latest generation climate models (CMIP6-class) are unable to resolve many of the physical processes acting in the polar regions. While some of these processes will remain unresolved for the foreseeable future, KeyPOCP will focus on a set of key processes that emerging simulations are starting to resolve. Specifically, KeyPOCP will quantify how dense water formation, shelf-basin exchange, air-sea interaction, and extreme precipitation events at high-latitudes depend on resolving the oceanic mesoscale and atmospheric storms at present and in a warmer future. To this end, KeyPOCP takes advantage of new high-resolution, fully coupled climate model simulations - including two global and one regional configurations - and existing observations in the Svalbard region and in the Weddell Sea.
