Climate response to a Bluer Arctic with increased newly-formed winter Sea ICe (BASIC)

The rapid decline of Arctic sea ice has led to a ‘bluer’ Arctic. While at the same time, the extent and the volume of newly-formed sea ice in winter are increasing; the climate science community has largely overlooked the latter unforeseen change, but it has potentially profound and lasting impacts on the Arctic and the Eurasian climate.   We anticipate that: (1) ‘Bluer’ Arctic is changing the respective roles of Arctic ocean temperature and sea ice in impacting the climate. (2) The increase of newly-formed wintertime sea ice year-after-year will promote the slowdown of the Atlantic Meridional Overturning Circulation (AMOC). (3) Vertical extent of Arctic warming is critical in resolving the debates on mechanisms driving the "warmer Arctic, colder Eurasia" winter climate pattern. In BASIC we will identify the mechanisms on the vertical propagation of Arctic ocean warming and assess the Eurasian winter climate response to deep Arctic warming (from ocean interior upwards to mid-troposphere) using coupled simulations.   We will further demonstrate that there is increased newly-formed Arctic sea ice in winter in the context of Arctic warming. We will then quantify the freshwater fluxes anomalies due to the increased newly-formed sea ice and assess their impacts on the Arctic ocean stratification and the AMOC. BASIC's results will therefore directly address (i) the grand challenges of the WCRP: ‘Melting Ice and Global Consequences’ and (ii) the United Nations (UN) Sustainable Development Goal 13 and Goal 14.   Through running large ensemble simulations, BASIC will identify (1) a 'threshold' of future Arctic sea ice state where there will be a role switching between the Arctic ocean temperature and sea ice in impacting the climate, and (2) the dominant effects of Arctic open seawaters on the climate variability due to their increasing capability to absorb and store energy.