Atlantic and Pacific SST experiments

Here we show results from the 3 Atlantic SST restoring experiments and the 3 Pacific restoring experiments, in which the SST increases by 3°C.

Here are the different model experiments with the corresponding color in the plots below:

D000 (blue solid curve) is the control run;
D012 (purple dashed curve) is the experiment in which the SST is restored to the mean climatology increased by 3°C in the North Atlantic Ocean (40-80N, 40W-20E); this is the wide Atlantic experiment;
D015 (red dashed curve) is the experiment in which the SST is restored to the mean climatology increased by 3°C in the northern North Atlantic Ocean (66-80N, 22W-20E); this is the middle Atlantic experiment;
D018 (light pink dashed curve) is the experiment in which the SST is restored to the mean climatology increased by 3°C at the Barents Sea Opening (70-77N, 16-20E); this is the small Atlantic experiment;
D021 (purple dashed curve) is the experiment in which the SST is restored to the mean climatology increased by 3°C in the North Pacific Ocean (30-66N, 120E-120W); this is the wide Pacific experiment;
D022 (red dashed curve) is the experiment in which the SST is restored to the mean climatology increased by 3°C in the northern Northeastern Pacific Ocean (40-50N, 180W-120W); this is the middle Pacific experiment;
D023 (light pink dashed curve) is the experiment in which the SST is restored to the mean climatology increased by 3°C at the Bering Strait (64-67N, 172-166W); this is the small Pacific experiment.

Results show that:

Fig. 1: the mean Atlantic OHT increases north of 60N in all experiments (with a more pronounced increase in the case of the North Atlantic experiment), decreases south of 60N in the 'wider domain' experiments (North Atlantic, northern North Atlantic, North Pacific and Northeastern Pacific) and increases south of 60N in the BSO and Bering Strait experiments;
Fig. 2: the spatial extent of the SST increase follows the domain used for the SST restoring, with a larger spatial extent in the SST experiments with the larger domain; also, the spatial distribution of the SST increase (averaged over 50 years) is not solely restricted to the North Pacific in the Pacific SST experiments (bottom row);
Figs. 3 and 4: the Arctic sea-ice area and volume decrease in all experiments, with a much more pronounced decrease in the 2 wide domain experiments (North Atlantic and North Pacific experiments; the decrease is quantitatively similar in these 2 experiments); the sea-ice area decrease in the Bering Strait experiment is stronger than in the northeastern Pacific experiment;
Fig. 5: the total OHT through all Arctic straits increases in all experiments, again with a much more pronounced increase in the 2 wide domain experiments; the OHT increase in the Bering Strait experiment is stronger than in the northeastern Pacific experiment, in agreement with the sea-ice area/volume results;
Fig. 6: the OHT at the BSO increases in all experiments, but much more clearly in the North Atlantic experiment;
Fig. 7: the OHT at the Bering Strait increases in all experiments, but more markedly in the North Pacific and Bering Strait experiments;
Fig. 8: the OHT at the Fram Strait generally increases in the wide and middle domain experiments, but with much lower amplitude compared to the increased OHT at the BSO and Bering Strait.
Fig. 9: the annual mean AMOC index at 26.5N decreases in the wide and middle domain experiments, which partly explains the decreased OHT south of 60N;
Fig. 10: the Atlantic meridional stream function (AMSF) strongly decreases in the 2 wide domain experiments (left column), decreases in the 2 middle domain experiments (middle column), doesn't change much in the BSO experiment (top right panel) and increases in the Bering Strait experiment (bottom right panel); interestingly, in the wide domain experiments (left column), the AMSF increases in the upper layers north of 60N, which is in agreement with the increased OHT north of 60N (Fig. 1); the overall AMSF decrease in the first 2 columns is in agreement with the reduced convection already identified in the mixed layer depth in Fig. 8 of the Atlantic SST restoring experiments;
Fig. 11: the March sea-ice concentration spatial patern loss is relatively similar between the wide/middle/small Atlantic and Pacific SST experiments, with higher loss at the sea-ice edge, with a more pronounced loss at the Atlantic (Pacific resp.) side in the Atlantic (Pacific resp.) experiments;
Fig. 12: the March sea-ice thickness spatial pattern loss is relatively similar between the wide/middle/small Atlantic and Pacific SST experiments, with loss everywhere in the Arctic;
Fig. 13: the September sea-ice concentration spatial pattern loss is relatively similar between the wide/middle/small domain Atlantic and Pacific SST experiments;
Fig. 14: the March sea-surface salinity (SSS) spatial pattern is relatively similar between the wide/middle domain Atlantic and Pacific SST experiments, with surface freshening in the western Arctic and northern North Atlantic and surface salinization in the eastern Arctic (similar as the PRIMAVERA coupled sea-ice loss experiments);
Fig. 15: the March sea-level pressure (SLP) spatial pattern shows differences between experiments, but the SLP increases over NW Europe / GIN Seas and over the Bering Sea, while it decreases over North America and central Asia;
Fig. 16: the total ocean volume transport (OVT) through all Arctic straits increases in the wide and middle domain experiments and slightly decreases in the small domain experiments;
Fig. 17: the OVT at the BSO increases in all experiments;
Fig. 18: the OVT at the Bering Strait decreases in the wide domain experiments and does not change much in the other experiments;
Fig. 19: the total OHT changes through all Arctic straits are mainly driven by the changes in temperature and the temperature-velocity covariance;
Fig. 20: for the Atlantic experiments, the OHT changes at the BSO are first driven by the changes in temperature, with considerable influence of the velocity and covariance contributions for the wide Atlantic experiment; for the Pacific experiments, the OHT changes at the BSO are shared by all 3 contributions;
Fig. 21: for the Atlantic experiments, the OHT changes at the Bering Strait are relatively small; for the Pacific experiments, the OHT changes at the Bering Strait are mainly driven by the changes in temperature.

Fig. 1: Latitudinal transect of mean Atlantic OHT averaged over 50 years for the control run and the 3 Atlantic (top panel) and 3 Pacific (bottom) experiments; the number in brackets is the difference in mean OHT between the experiment and the control (CTRL)

Fig. 2: Maps of difference in mean March SST, averaged over 50 years, between the Atlantic (top row) / Pacific (bottom) experiments and the control run

Fig. 3: Mean seasonal cycle of Arctic sea-ice area (SIA), averaged over 50 years, for the control run and the 3 Atlantic (left panel) and 3 Pacific (right panel) experiments; the numbers in brackets are the differences in mean SIA in March/September between the experiment and the control (CTRL)

Fig. 4: Mean seasonal cycle of Arctic sea-ice volume (SIV), averaged over 50 years, for the control run and the 3 Atlantic (left panel) and 3 Pacific (right panel) experiments; the numbers in brackets are the differences in mean SIV in March/September between the experiment and the control (CTRL)

Fig. 5: Time series of total ocean heat transport (OHT) through all Arctic straits for the control run and the 3 Atlantic (top panel) and 3 Pacific (bottom panel) experiments; the number in brackets is the difference in mean OHT between the experiment and the control (CTRL)

Fig. 6: Time series of ocean heat transport (OHT) at the Barents Sea Opening (BSO) for the control run and the 3 Atlantic (top panel) and 3 Pacific (bottom panel) experiments; the number in brackets is the difference in mean OHT between the experiment and the control (CTRL)

Fig. 7: Time series of ocean heat transport (OHT) at the Bering Strait for the control run and the 3 Atlantic (top panel) and 3 Pacific (bottom panel) experiments; the number in brackets is the difference in mean OHT between the experiment and the control (CTRL)

Fig. 8: Time series of ocean heat transport (OHT) at the Fram Strait for the control run and the 3 Atlantic (top panel) and 3 Pacific (bottom panel) experiments; the number in brackets is the difference in mean OHT between the experiment and the control (CTRL)

Fig. 9: Time series of annual mean Atlantic Meridional Overturning Circulation (AMOC) index at 26.5N (maximum Atlantic meridional stream function between 900 and 1200m) for the control run and the 3 Atlantic (top panel) and 3 Pacific (bottom panel) experiments

Fig. 10: Vertical profiles of the mean Atlantic meridional stream function (AMSF) in the control run (top left panel) and of the difference in the mean AMSF between the Atlantic (middle row) / Pacific (bottom row) experiments and the control run, averaged over 50 years

Fig. 11: Maps of difference in mean March sea-ice concentration (SIC), averaged over 50 years, between the Atlantic (top row) / Pacific (bottom) experiments and the control run

Fig. 12: Maps of difference in mean March sea-ice thickness (SIT), averaged over 50 years, between the Atlantic (top row) / Pacific (bottom) experiments and the control run

Fig. 13: Maps of difference in mean September sea-ice concentration (SIC), averaged over 50 years, between the Atlantic (top row) / Pacific (bottom) experiments and the control run

Fig. 14: Maps of difference in mean March sea-surface salinity (SSS), averaged over 50 years, between the Atlantic (top row) / Pacific (bottom) experiments and the control run

Fig. 15: Maps of difference in mean March sea-level pressure (SLP), averaged over 50 years, between the Atlantic (top row) / Pacific (bottom) experiments and the control run

Fig. 16: Time series of total ocean volume transport (OVT) through all Arctic straits for the control run and the 3 Atlantic (top panel) and 3 Pacific (bottom panel) experiments; the number in brackets is the difference in mean OVT between the experiment and the control (CTRL)

Fig. 17: Time series of ocean volume transport (OVT) at the Barents Sea Opening (BSO) for the control run and the 3 Atlantic (top panel) and 3 Pacific (bottom panel) experiments; the number in brackets is the difference in mean OVT between the experiment and the control (CTRL)

Fig. 18: Time series of ocean volume transport (OVT) at the Bering Strait for the control run and the 3 Atlantic (top panel) and 3 Pacific (bottom panel) experiments; the number in brackets is the difference in mean OVT between the experiment and the control (CTRL)

Fig. 19: Time series of changes in total ocean heat transport (OHT) through all Arctic straits between the sensitivity experiments and the control run (CTRL): total changes (top left panel), changes due to velocity (top right panel), changes due to temperature (bottom left panel), changes due to their covariance (bottom right panel); the number in brackets is the mean change between the sensitivity experiment and the control

Fig. 20: Time series of changes in ocean heat transport (OHT) at the Barents Sea Opening (BSO) between the sensitivity experiments and the control run (CTRL): total changes (top left panel), changes due to velocity (top right panel), changes due to temperature (bottom left panel), changes due to their covariance (bottom right panel); the number in brackets is the mean change between the sensitivity experiment and the control

Fig. 21: Time series of changes in ocean heat transport (OHT) at the Bering Strait between the sensitivity experiments and the control run (CTRL): total changes (top left panel), changes due to velocity (top right panel), changes due to temperature (bottom left panel), changes due to their covariance (bottom right panel); the number in brackets is the mean change between the sensitivity experiment and the control

Fig. 22: Vertical profiles of the mean North Atlantic Ocean potential temperature in the control run (top left panel) and of the difference in the mean ocean temperature between the Atlantic (middle row) / Pacific (bottom row) experiments and the control run, averaged over 50 years

Fig. 23: Vertical profiles of the mean North Pacific Ocean potential temperature in the control run (top left panel) and of the difference in the mean ocean temperature between the Atlantic (middle row) / Pacific (bottom row) experiments and the control run, averaged over 50 years

Fig. 24: Vertical profiles of the mean North Atlantic Ocean salinity in the control run (top left panel) and of the difference in the mean ocean salinity between the Atlantic (middle row) / Pacific (bottom row) experiments and the control run, averaged over 50 years

Fig. 25: Vertical profiles of the mean North Pacific Ocean salinity in the control run (top left panel) and of the difference in the mean ocean salinity between the Atlantic (middle row) / Pacific (bottom row) experiments and the control run, averaged over 50 years

Fig. 26: Vertical profiles of the mean North Atlantic Ocean u-comp. of velocity in the control run (top left panel) and of the difference in the mean ocean u-comp. of velocity between the Atlantic (middle row) / Pacific (bottom row) experiments and the control run, averaged over 50 years

Fig. 27: Vertical profiles of the mean North Atlantic Ocean v-comp of velocity in the control run (top left panel) and of the difference in the mean ocean v-comp. of velocity between the Atlantic (middle row) / Pacific (bottom row) experiments and the control run, averaged over 50 years

Important note: These figures were produced by D. Docquier and constitute preliminary results (not published in papers).