Heat Balance in the Nordic Seas in a Global 1/12° Coupled Model

Abstract

The Nordic Seas are a gateway to the Arctic Ocean, where Atlantic water undergoes a strong cooling during its transit. Here we investigate the heat balance of these regions in the high resolution Met Office Global Coupled Model GC3 with a 1/12_ grid. The GC3 model reproduces resolution Met Office Global Coupled Model GC3 with a 1/12_ grid. The GC3 model reproduces the contrasted ice conditions and ocean heat loss between the eastern and western regions of the Nordic Seas. In the west (Greenland and Iceland seas), the heat loss experienced by the ocean is stronger than the atmospheric heat gain, because of the cooling by ice melt. The latter is a major contribution to the heat loss over the path of the East Greenland Current and west of Svalbard. In the model, surface fluxes balance the convergence of heat in each of the eastern and western regions. The net east-west heat exchange, integrated from Fram Strait to Iceland, is relatively small: the westward heat transport of the Return Atlantic Current over Knipovich Ridge balances the eastward heat transport by the East Icelandic Current. Time fluctuations, including eddies, are a significant contribution to the net heat transports. The eddy flux represents about 20% of the total heat transport in Denmark Strait and across Knipovich Ridge. The coupled ocean-atmosphere-ice model may overestimate the heat imported from the Atlantic and exported to the Arctic by 10 or 15%. This confirms the tendency toward higher northward heat transports as model resolution is refined, which will impact scenarios of future climate.

Heat Transport by Mesoscale Eddies in the Norwegian and Greenland Seas

“…Eddies also play an important role further north, where one of the westward recirculations of the AW in the Fram Strait is considered to be eddy-driven (Boyd & D'Asaro, 1994;Hattermann et al, 2016;Hofmann et al, 2021;Nilsen et al, 2006;von Appen et al, 2015). However, except for some model studies (see, e.g., Hattermann et al, 2016;Spall et al, 2021;Treguier et al, 2021;Wekerle et al, 2020), the effect of coherent eddies on heat redistribution in these areas has not been evaluated and forms the core of this study. Using the AVISO satellite altimetry data, we detected over 900,000 mesoscale eddies in the study region from 1993 to 2018.…”

“…One of the important sources of the heat loss from the NwASC is the oceanic advection into the Barents Sea with the Nordcape Current (NCC), which is 70 ± 20 TW during the recent decades (Tb = 0°C, Bashmachnikov et al., 2018; Smerdsrud et al., 2010). The sum of the oceanic heat loss to the atmosphere and radiation balance over the Norwegian Sea ranges between 50 and 150 W m −2 , depending on the season and the position, with the annual and basin‐mean heat leaving the ocean surface of around 40–70 W m −2 (Latarius & Quadfasel, 2016; Spall et al., 2021; Treguier et al., 2021). This gives an overall heat loss of 30–60 TW at the ocean surface over the eastern Norwegian Sea (regions A and B in Figure 1).…”

Role of air-sea heat flux on the transformation of Atlantic Water encircling the Nordic Seas

“…We now seek to determine the impact of air–sea heat exchange on the transformation of AW along the two northward-flowing branches of the NwAC. Using high-resolution model simulations, recent studies have investigated the heat distribution and balance in the Nordic Seas 16 , 27 , 28 , which has shed light on the mechanisms regulating the rim current transformation. However, uncertainty remains due to the problem of accurately representing the NwAFC in these models.…”