The scientific community still has no consensus on if and how Arctic warming and sea ice loss can influence weather and climate in the Northern Hemisphere. The BASIC project sets out to better understand the climate response to Arctic change, especially focusing on the new Arctic characterized by more open water in summer (hence bluer) and increased newly-formed sea ice in winter. This latter change has been mostly overlooked, but it has potentially profound climate impacts.
Sea ice change can affect the Atlantic Meridional Overturning Circulation (AMOC) through modulating ocean salinity: AMOC is a large ocean current driven by the sinking of denser water in the northern North Atlantic. It carries tropic warm water into the North Atlantic and thus along the Norwegian coast, but has been weakened by the increase of freshwater due to long-term sea ice melting. As multi-year ice is decreasing rapidly, the recent and future increasing newly-formed ice may change such impacts.
A bluer Arctic may change the respective roles of Arctic Ocean temperature and sea ice in impacting climate. Model experiments have shown that the climate responses to an ice-free state are appreciably distinct from an ice-covered state. We expect that, before the Arctic reaches an ice-free state, Arctic sea ice may shrink stepwise and go through a threshold where ocean temperature takes over to impact climate. Identifying this threshold is important for climate prediction.
Bluer Arctic with increased newly-formed winter sea ice is concurrent with an Arctic warming extending downwards into ocean interior and upwards to mid-troposphere (~5 km). But the climate models have divergent abilities to simulate the observed deep Arctic warming, which caused debates in this field. BASIC will develop a new methodology to conquer this problem.
The BASIC project will analyze available observed and simulated datasets and run new experiments with the Norwegian Earth System Model to address the above issues.