Abstract
The importance of considering ocean surface currents in ice-ocean stress calculation in the North Atlantic Ocean and Arctic sea ice is investigated for the first time using a global coupled ocean-sea ice model. Considering ocean surface currents in ice-ocean stress calculation weakens the ocean surface stress and Ekman pumping by about 7.7 and 15% over the North Atlantic Ocean, respectively. It also significantly reduces the mechanical energy input to ageostrophic and geostrophic currents, and weakens the mean and eddy kinetic energy by reducing the energy conversion rates of baroclinic and barotropic pathways. Furthermore, the strength of the Atlantic Meridional Overturning Circulation (AMOC), the Nordic Seas MOC, and the North Atlantic subpolar gyre are found to be reduced considerably (by 14.3, 31.0, and 18.1%, respectively). The weakened AMOC leads to a 0.12 PW reduction in maximum northward ocean heat transport, resulting in a reduced surface heat loss and lower sea surface temperature over the North Atlantic Ocean. This reduction also leads to a shrink in sea ice extent and an attenuation of sea ice thickness. These findings highlight the importance of properly considering both the geostrophic and ageostrophic components of ocean surface currents in ice-ocean stress calculation on ocean circulation and climate studies.
Highlights
Sea ice variability influences both the buoyancy and momentum fluxes between the atmosphere and the ocean
When the ocean surface currents are excluded from the ice-ocean stress calculation, an increase of timemean ocean surface stress occurs in regions covered by sea ice, especially in the Baffin Bay, the western boundary areas of the Nordic Seas, and the Labrador Sea (Figure 1B)
We have investigated for the first time the impact of considering ocean surface currents in the iceocean stress calculation on the North Atlantic Ocean and Arctic sea ice using a global coupled ocean-sea ice model with approximately 18-km resolution
Summary
Sea ice variability influences both the buoyancy and momentum fluxes between the atmosphere and the ocean. The important implications of considering ocean surface currents in ice-ocean stress (τIO) calculation on freshwater content, depth, and strength of the Beaufort Gyre have been more recently recognized (Kwok and Morison, 2017; Meneghello et al, 2017, 2018a,b; Dewey et al, 2018; Zhong et al, 2018; Wang et al, 2019). The effects of considering ocean surface currents in ice-ocean stress calculation on sea surface fluxes, momentum transfer from wind to sea ice, and the underlying ocean, subpolar gyres, MLD, and MOCs in the Nordic Seas and the North Atlantic Ocean have not been adequately studied. Mean outputs for ocean temperature and salinity, 5-day mean outputs for ocean currents, and daily outputs for sea ice variables were analyzed
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