The Arctic has undergone dramatic changes in sea ice cover and the hydrologic cycle, both of which strongly impact the freshwater storage in, and export from, the Arctic Ocean. Here we analyze Arctic freshwater storage and fluxes in seven climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) and assess their performance over the historical period (1980–2000) and in two future emissions scenarios, SSP1‐2.6 and SSP5‐8.5. Similar to CMIP5, substantial differences exist between the models' Arctic mean states and the magnitude of their 21st century storage and flux changes. In the historical simulation, most models disagree with observations over 1980–2000. In both future scenarios, the models show an increase in liquid freshwater storage and a reduction in solid storage and fluxes through the major Arctic gateways (Bering Strait, Fram Strait, Davis Strait, and the Barents Sea Opening) that is typically larger for SSP5‐8.5 than SSP1‐2.6. The liquid fluxes are driven by both volume and salinity changes, with models exhibiting a change in sign (relative to 1980–2000) of the freshwater flux through the Barents Sea Opening by mid‐century, little change in the Bering Strait flux, and increased export from the remaining straits by the end of the 21st century. In the straits west of Greenland (Nares, Barrow, and Davis straits), the models disagree on the behavior of the liquid freshwater export in the early‐to‐mid 21st century due to differences in the magnitude and timing of a simulated decrease in the volume flux.
Arctic Ocean warming and sea ice loss are closely linked to increased ocean heat transport (OHT) into the Arctic and changes in surface heat fluxes. To quantitatively assess their respective roles, we use the 100-member Community Earth System Model, version 2 (CESM2), Large Ensemble over the 1920–2100 period. We first examine the Arctic Ocean warming in a heat budget framework by calculating the contributions from heat exchanges with atmosphere and sea ice and OHT across the Arctic Ocean gateways. Then we quantify how much anomalous heat from the ocean directly translates to sea ice loss and how much is lost to the atmosphere. We find that Arctic Ocean warming is driven primarily by increased OHT through the Barents Sea Opening, with additional contributions from the Fram Strait and Bering Strait OHTs. These OHT changes are driven mainly by warmer inflowing water rather than changes in volume transports across the gateways. The Arctic Ocean warming driven by OHT is partially damped by increased heat loss through the sea surface. Although absorbed shortwave radiation increases due to reduced surface albedo, this increase is compensated by increasing upwelling longwave radiation and latent heat loss. We also explicitly calculate the contributions of ocean–ice and atmosphere–ice heat fluxes to sea ice heat budget changes. Throughout the entire twentieth century as well as the early twenty-first century, the atmosphere is the main contributor to ice heat gain in summer, though the ocean’s role is not negligible. Over time, the ocean progressively becomes the main heat source for the ice as the ocean warms.
Arctic Ocean warming and sea ice loss are closely linked to increased ocean heat transport (OHT) into the Arctic and changes in surface heat fluxes. Here we use 100 simulations from the same climate model to analyze future warming and sea ice loss. We find that Arctic Ocean warming is primarily driven by increased OHT through the Barents Sea Opening, though the Fram and Bering Straits are also important. This increased OHT is primarily due to warmer inflowing water rather than changing ocean currents. This ocean heat gain is partially compensated by heat loss through the sea surface. During the twentieth century and early twenty-first century, sea ice loss is mainly linked to heat transferred from the atmosphere; however, over time, the ocean progressively becomes the most important contributor.
- NSF-PAR ID:
- 10487694
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of Climate
- Volume:
- 37
- Issue:
- 4
- ISSN:
- 0894-8755
- Format(s):
- Medium: X Size: p. 1431-1448
- Size(s):
- ["p. 1431-1448"]
- Sponsoring Org:
- National Science Foundation
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