Greenland's Island Rule and the Arctic Ocean circulation

Abstract

In order to explain observed southward water transport of 2-3 Sv through Davis Strait, a simple extension of Godfrey's (1989) Island Rule and a 2-D idealized numerical model simulations were made for the flow around Greenland. Godfrey's theory has been extended to permit inclusion of Bering Strait inflow and bottom friction to represent the dissipation supplied by the porous Canadian Archipelago in the modeled flow west of Greenland. In both models, the forcing has been applied in a quasi-steady manner to the circulation via climatologic wind stresses and using wind forcing for the high and low Arctic Oscillation (AO) index states. It is found that climatologic wind produces an overall cyclonic flow around Greenland. This flow is increased under winds of a positive AO index and reduced, even becoming anti-cyclonic during a negative AO phase. Model experiments show that increase of model friction results in the blocking of flow west of Greenland (decrease of water transport in Davis Strait) and a shift of more flow to the east of Greenland. Model tuning to agree with direct measurements of transport in the Davis Strait is sensitive to both the forcing and the dissipation. Numerical experiments are also run to illustrate the dependence of the physics on bathymetric variations from a flat 200-m deep ocean, on lateral friction, and on properly resolving the flow in the archipelago with the numerical model. The circum-Greenland transport by winds can exceed the Bering Strait inflow and account for most of the observed flow (ca. −2.5 Sv) to the west of Greenland. Poor representation of Canada Strait opening in the numerical models can result in the intensification of the East Greenland Current and in the reduction of the Atlantic water inflow to the Arctic Ocean.