Mechanisms of Ocean Heat Anomalies in the Norwegian Sea

Asbjørnsen, Helene; Årthun, Marius; Skagseth, Øystein; Eldevik, Tor

doi:10.1029/2018jc014649

Cited by 53 publications

(56 citation statements)

References 73 publications

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“…Concerning local forcing, the stronger winds lead to stronger heat loss by increasing the turbulent fluxes of sensible and latent heat. Asbjørnsen et al () have recently shown that 50 % of the variability in the Nordic Seas ocean heat content can be attributed to local surface forcing, and although we have not investigated this in depth, we speculate that the changes in heat content arise due to a combination of advection and local forcing. Note that the accelerated Norwegian Current (and resulting greater heat transport from the south) is mainly excluded from the Nordic Seas box shown in Figure .…”

Section: Discussionsupporting

confidence: 92%

Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations

et al. 2019

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Multimodel Arctic Ocean “climate response function” experiments are analyzed in order to explore the effects of anomalous wind forcing over the Greenland Sea (GS) on poleward ocean heat transport, Atlantic Water (AW) pathways, and the extent of Arctic sea ice. Particular emphasis is placed on the sensitivity of the AW circulation to anomalously strong or weak GS winds in relation to natural variability, the latter manifested as part of the North Atlantic Oscillation. We find that anomalously strong (weak) GS wind forcing, comparable in strength to a strong positive (negative) North Atlantic Oscillation index, results in an intensification (weakening) of the poleward AW flow, extending from south of the North Atlantic Subpolar Gyre, through the Nordic Seas, and all the way into the Canadian Basin. Reconstructions made utilizing the calculated climate response functions explain ∼50% of the simulated AW flow variance; this is the proportion of variability that can be explained by GS wind forcing. In the Barents and Kara Seas, there is a clear relationship between the wind‐driven anomalous AW inflow and the sea ice extent. Most of the anomalous AW heat is lost to the atmosphere, and loss of sea ice in the Barents Sea results in even more heat loss to the atmosphere, and thus effective ocean cooling. Release of passive tracers in a subset of the suite of models reveals differences in circulation patterns and shows that the flow of AW in the Arctic Ocean is highly dependent on the wind stress in the Nordic Seas.

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Section: Discussionsupporting

confidence: 92%

Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations

et al. 2019

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“…However, this does not rule out that atmospheric circulation anomalies may also have helped to maintain warm ocean temperatures in the Nordic Seas since mid-2000s, resulting in the stagnant period instead of the cooling seen in the SPNA. This may be consistent with conclusions from a recent study by Asbjørnsen et al (2018), which reported that local forcing from air-sea heat fluxes are important for modulating the anomalies on their northward path. Although we have only speculated on the cause for this stagnant period, our simple model of heat convergence reproduced the decadal heat content variability in the eastern Nordic Seas reasonably well, despite the observed disconnection from the SPNA.…”

Section: Connection To the Upstream Subpolar North Atlanticsupporting

confidence: 93%

“…Several observational studies have found that the surface heat flux can only explain a smaller part of the low-frequency variations of the AW heat content in the Nordic Seas (Carton et al, 2011;Skagseth and Mork, 2012;Shi et al, 2017). A study of a physically consistent ocean state estimate also show that surface heat flux is not the main source of AW heat content interannual variability (Asbjørnsen et al, 2018). Although the surface heat flux data is not conclusive, we argue that the surface heat flux is not the main source of the change in decadal trends.…”

Section: Simple Heat Budgetmentioning

confidence: 98%

“…Our considerations show that AW temperature variations can be more important for the ocean heat convergence than variations in AW volume transport. However, the ocean heat transport variations in sections across the AW, such as the Svinøy Section, tend to be dominated by variations in the volume transport (Asbjørnsen et al, 2018). The reason is that there is a net volume transport across the sections, which requires the heat transport to be defined relative to a reference temperature.…”

Section: Conceptual Model Of Ocean Heat Convergencementioning

confidence: 99%

“…This reference temperature, characterising a return flow, is usually taken to be 0 • C for AW heat transport in the Nordic Seas (Asbjørnsen et al, 2018). Using a reference temperature of 0 • C to estimate the heat transport anomaly in Eq.…”

Section: Conceptual Model Of Ocean Heat Convergencementioning

confidence: 99%

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Mechanisms of the time-varying sea surface height and heat content trends in the eastern Nordic Seas

Broomé

Chafik

Nilsson

2019

Preprint

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Abstract. The Nordic Seas is the main ocean conveyor of heat between the North Atlantic Ocean and the Arctic Ocean. Although the decadal variability of the Subpolar North Atlantic has been given significant attention lately, especially regarding the cooling trend since mid-2000s, less is known about the potential connection downstream in the northern basins. Using sea surface heights from satellite altimetry over the past 25 years (1993–2017), we find significant variability on multiyear-to-decadal time scales in the Nordic Seas. In particular, the regional trends in sea surface height show signs of a slowdown since mid-2000s as compared to the rapid increase in the preceding decade since early 1990s. This change is most prominent in the Atlantic origin waters in the eastern Nordic Seas and is closely linked, as estimated from hydrography, to heat content. Furthermore, we formulate a simple heat budget for the eastern Nordic Seas to discuss the relative importance of local and remote sources of variability; advection of temperature anomalies in the Atlantic inflow is found to be the main mechanism. A conceptual model of ocean heat convergence, with only upstream temperature measurements at the inflow to the Nordic Seas as input, is able to reproduce key aspects of the decadal variability of the Nordic Seas' heat content. Based on these results, we argue that there is a strong connection with the upstream Subpolar North Atlantic. However, although the shift in trends in the mid-2000s is coincident in the Nordic Seas and the Subpolar North Atlantic, the eastern Nordic Seas has not seen a reversal of trends but instead maintain elevated sea surface heights and heat content in the recent decade considered here.

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Intensification of the Atlantic Water supply to the Arctic Ocean through Fram Strait induced by Arctic sea ice decline

Wang

Wekerle

Wang

et al. 2019

Preprint

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Substantial changes have occurred in the Arctic Ocean in the last decades. Not only sea ice has retreated significantly, but also the ocean at middepth showed a warming tendency. By using simulations we identified a mechanism that intensifies the upward trend in ocean heat supply to the Arctic Ocean through Fram Strait. The reduction in sea ice export through Fram Strait induced by Arctic sea ice decline increases the salinity in the Greenland Sea, which lowers the sea surface height and strengthens the cyclonic gyre circulation in the Nordic Seas. The Atlantic Water volume transport to the Nordic Seas and Arctic Ocean is consequently strengthened. This enhances the warming trend of the Arctic Atlantic Water layer, potentially contributing to the Arctic "Atlantification." Our study suggests that the Nordic Seas can play the role of a switchyard to influence the heat budget of the Arctic Ocean. Plain Language SummaryThe Arctic sea ice decline is among the key indications of climate change, which has strong impacts on the environment, human beings, and biodiversity. In this paper we found that the Arctic sea ice decline at the surface can even cause Arctic Ocean warming at middepth by intensifying the upward trend of ocean heat supply to the Arctic Ocean through Fram Strait. The Nordic Seas play the role of a switchyard for the involved processes: The sea ice decline reduces the sea ice export through Fram Strait, which further increases the salinity in the Greenland Sea. Consequently, in the Nordic Seas the sea surface height decreases and the gyre circulation strengthens. These changes then increase the Atlantic Water inflow to the Nordic Seas and the Arctic Ocean, causing significant warming in the Atlantic Water layer of the Arctic Ocean. The changes in the ocean heat budget have strong implications on potential feedbacks to sea ice decline through basal melting in a future warming climate. The intensification of the Atlantic Water volume transport through Fram Strait can impact not only the Arctic heat budget but also potentially the nutrient budget and the primary production.

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Mechanisms of Ocean Heat Anomalies in the Norwegian Sea

Cited by 53 publications

References 73 publications

Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations

Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations

Mechanisms of the time-varying sea surface height and heat content trends in the eastern Nordic Seas

Intensification of the Atlantic Water supply to the Arctic Ocean through Fram Strait induced by Arctic sea ice decline

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