Bjerknes compensation in the Bergen Climate Model

Outten, Stephen; Esau, Igor

doi:10.1007/s00382-016-3447-2

Cited by 15 publications

(17 citation statements)

References 33 publications

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“…Our results demonstrate that Bjerknes compensationopposing changes in oceanic and atmospheric heat transports-is a governing mechanism in equilibrium climate states, with compensation rates between 79% and 93% at 70 • N . In earlier studies, the importance of Bjerknes compensation was already demonstrated for climate variations on decadal time scales (Shaffrey and Sutton 2006;van der Swaluw et al 2007;Jungclaus and Koenigk 2010;Outten and Esau 2016); on interannual time scales the compensation mechanism was found to be negligible (Shaffrey and Sutton 2004). This implies that the degree of compensation increases for longer time scales.…”

Section: Discussionmentioning

confidence: 88%

Oceanic heat transport into the Arctic under high and low $$\hbox {CO}_2$$ forcing

2019

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Enhanced ocean heat transport into the Arctic is linked to stronger future Arctic warming and polar amplification. To quantify the impact of ocean heat transport on Arctic climate, it is imperative to understand how its magnitude and the associated mechanisms change in other climate states. This paper therefore assesses the ocean heat transport into the Arctic at 70 • N for climates forced with a broad range of carbon dioxide concentration levels, ranging from one-fourth to four times modern values. We focused on ocean heat transports through the Arctic entrances (Bering Strait, Canadian Archipelago, and Nordic Seas) and identified relative contributions of volume and temperature to these changes. The results show that ocean heat transport differences across the five climate states are dominated by heat transport changes in the Nordic Seas, although in the warmest climate state heat transport through the Bering Strait plays an almost equally important role. This is primarily caused by changes in horizontal currents owing to anomalous wind responses and to differential advection of thermal anomalies. Changes in sea ice cover play a prominent role by modulating the surface heat fluxes and the impact of wind stresses on ocean currents. The Atlantic meridional overturning circulation and its associated heat transport play a more modest role in the ocean heat transport into the Arctic. The net effect of these changes is that the poleward ocean heat transport at 70 • N strongly increases from the coldest climate to the warmest climate state.

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Section: Discussionmentioning

confidence: 88%

Oceanic heat transport into the Arctic under high and low $$\hbox {CO}_2$$ forcing

2019

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“…The previously described Bjerknes compensation (Bjerknes 1964) explains the negative correlations between SAT and AHT on decadal and multidecadal time scales. For Bjerknes compensation, marginal ice zones are critical (Van der Swaluw et al 2007;Outten and Esau 2017). Increased OHT leads to a decrease of sea ice in these zones.…”

Section: Time-scale Dependencymentioning

confidence: 99%

Differences between Arctic Interannual and Decadal Variability across Climate States

Reusen

Linden

2019

Journal of Climate

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Long-term climate variations have the potential to amplify or dampen (human-induced) trends in temperature. Understanding natural climate variability is therefore of vital importance, especially since the variability itself may change with a changing climate. Here, we quantify the magnitude and other characteristics of interannual to decadal variability in Arctic temperature and their dependence on the climate state. Moreover, we identify the processes responsible for the state dependency of the variations, using five quasi-equilibrium climate simulations of a state-of-the-art global climate model with 0.25, 0.5, 1, 2, and 4 times present-day atmospheric CO2 forcing. The natural fluctuations in Arctic temperature, including their dependence on the state of the climate, are linked to anomalous atmospheric and oceanic heat transports toward the Arctic. Model results suggest that atmospheric heat transport leads (and also controls) Arctic temperature variations on interannual time scales, whereas oceanic transport is found to govern the fluctuations on decadal time scales. This time-scale transition of atmospheric to oceanic dominance for Arctic temperature variations is most obvious when there is interannual to decadal variability in Arctic sea ice cover. In warm climates (without Arctic sea ice cover), there is no correlation between oceanic transport and surface air temperature on any time scale. In cold climates (with full Arctic sea ice cover), interaction between ocean and atmosphere is limited, leaving poleward atmospheric heat transport to be the primary driver on all time scales (interannual and decadal).

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“…The mechanism of the BJC during this period is similar to that from freshwater hosing in the North Atlantic (Yang et al 2013(Yang et al , 2017). An important implication of this study is that under the present-day global warming, we still expect that the BJC plays a stabilizing role in containing Earth's climate shift, as long as there is plenty of sea ice (or continental ice) to melt (Jungclaus and Koenigk 2010;Outten and Esau 2017). The change in hydrological cycle appears to cool the global surface temperature, slowing down the temperature rising in a warming world.…”

Section: Conclusion and Discussionmentioning

confidence: 85%

“…8b). This situation is also studied in Jungclaus and Koenigk (2010) and Outten and Esau (2017). Accordingly, the net freshwater into the ocean in the sea ice formation region declines (Fig.…”

Section: Freshwater Flux and Its Roles In Mhtmentioning

confidence: 90%

Understanding Bjerknes Compensation in Meridional Heat Transports and the Role of Freshwater in a Warming Climate

et al. 2018

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The Bjerknes compensation (BJC) under global warming is studied using a simple box model and a coupled Earth system model. The BJC states the out-of-phase changes in the meridional atmosphere and ocean heat transports. Results suggest that the BJC can occur during the transient period of global warming. During the transient period, the sea ice melting in the high latitudes can cause a significant weakening of the Atlantic meridional overturning circulation (AMOC), resulting in a cooling in the North Atlantic. The meridional contrast of sea surface temperature would be enhanced, and this can eventually enhance the Hadley cell and storm-track activities in the Northern Hemisphere. Accompanied by changes in both ocean and atmosphere circulations, the northward ocean heat transport in the Atlantic is decreased while the northward atmosphere heat transport is increased, and the BJC occurs in the Northern Hemisphere. Once the freshwater influx into the North Atlantic Ocean stops, or the ocean even loses freshwater because of strong heating in the high latitudes, the AMOC would recover. Both the atmosphere and ocean heat transports would be enhanced, and they can eventually recover to the state of the control run, leading to the BJC to become invalid. The above processes are clearly demonstrated in the coupled model CO2 experiment. Since it is difficult to separate the freshwater effect from the heating effect in the coupled model, a simple box model is used to understand the BJC mechanism and freshwater’s role under global warming. In a warming climate, the freshwater flux into the ocean can cool the global surface temperature, mitigating the temperature rise. Box model experiments indicate clearly that it is the freshwater flux into the North Atlantic that causes out-of-phase changes in the atmosphere and ocean heat transports, which eventually plays a stabilizing role in global climate change.

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Bjerknes compensation in the Bergen Climate Model

Cited by 15 publications

References 33 publications

Oceanic heat transport into the Arctic under high and low $$\hbox {CO}_2$$ forcing

Oceanic heat transport into the Arctic under high and low $$\hbox {CO}_2$$ forcing

Differences between Arctic Interannual and Decadal Variability across Climate States

Understanding Bjerknes Compensation in Meridional Heat Transports and the Role of Freshwater in a Warming Climate

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