Does Arctic sea ice reduction foster shelf-basin exchange?

Area of Science:

• Oceanography
• Climate Science
• Arctic Studies

Background:

• Arctic ice conditions are shifting from multi-year to first-year ice, potentially increasing sea ice freezing and salt flux.
• This shift raises concerns about catastrophic consequences for the global thermohaline circulation (THC) due to diminishing Arctic sea ice.

Purpose of the Study:

• To investigate whether predicted catastrophic consequences for the global thermohaline circulation (THC) due to Arctic sea ice loss are inevitable.
• To assess the role of enhanced ice production and shelf-basin exchange in replenishing dense water in a warmer climate.

Main Methods:

• A dual modeling study combining a pan-Arctic coupled ice-ocean general circulation model (GCM) and a regional model.
• The GCM simulated baseline buoyancy forcing from columnar ice formation over 30 years.
• A regional model examined cascading conditions in the Pacific and Atlantic sectors, incorporating sub-grid processes and prescribed bathymetry/stratification.

Main Results:

• Enhanced ice formation's impact on dense water cascading is geographically dependent, influenced by shelf-basin bathymetry.
• In the Pacific sector, strong density stratification limits the deepening of shelf-origin water.
• In the Atlantic sector, a 1.5x increase in salt flux tripled shelf-slope volume flux, potentially substituting for reduced dense water formation in the Greenland, Iceland, and Norwegian (GIN) seas.

Conclusions:

• The predicted catastrophic consequences for the global thermohaline circulation (THC) may not occur.
• Dense water formation on Arctic shelves and subsequent cascading can replenish the deep ocean, especially in the Atlantic sector.
• Warming climate impacts on THC are moderated by Arctic shelf processes, contingent on location and bathymetry.