Skillful prediction of northern climate provided by the ocean

Årthun, Marius; Eldevik, Tor; Viste, Ellen; Drange, Helge; Furevik, Tore; Johnson, H. L.; Keenlyside, Noel

doi:10.1038/ncomms15875

Cited by 107 publications

(89 citation statements)

References 72 publications

(164 reference statements)

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“…Variability on decadal time scales of temperature and salinity associated with the warm Atlantic water pathway is of great scientific interest, as anomalies of such properties can have profound impact on the ocean climate along the pathway, and potentially on northwestern European climate (e.g., Collins and Sinha 2003;Årthun et al 2017). In this study, our main purpose is to investigate to what extent a forced global ocean-sea ice model is able to represent known characteristics of the Atlantic water pathway.…”

Section: Discussionmentioning

confidence: 99%

“…The poleward propagation of thermohaline anomalies is considered to be a main source of climate predictability (Årthun and Eldevik 2016;Årthun et al 2017;Yeager and Robson 2017). The purpose of this study is twofold: (1) We investigate how properties associated with the warm Atlantic water is expressed along its pathway, using observational data and a forced global ocean-sea ice model.…”

Section: Discussionmentioning

confidence: 99%

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Variability along the Atlantic water pathway in the forced Norwegian Earth System Model

et al. 2018

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The growing attention on mechanisms that can provide predictability on interannual-to-decadal time scales, makes it necessary to identify how well climate models represent such mechanisms. In this study we use a high (0.25° horizontal grid) and a medium (1°) resolution version of a forced global ocean-sea ice model, utilising the Norwegian Earth System Model, to assess the impact of increased ocean resolution. Our target is the simulation of temperature and salinity anomalies along the pathway of warm Atlantic water in the subpolar North Atlantic and the Nordic Seas. Although the high resolution version has larger biases in general at the ocean surface, the poleward propagation of thermohaline anomalies is better resolved in this version, i.e., the time for an anomaly to travel northward is more similar to observation based estimates. The extent of these anomalies can be rather large in both model versions, as also seen in observations, e.g., stretching from Scotland to northern Norway. The easternmost branch into the Nordic and Barents Seas, carrying warm Atlantic water, is also improved by higher resolution, both in terms of mean heat transport and variability in thermohaline properties. A more detailed assessment of the link between the North Atlantic Ocean circulation and the thermohaline anomalies at the entrance of the Nordic Seas reveals that the high resolution is more consistent with mechanisms that are previously published. This suggests better dynamics and variability in the subpolar region and the Nordic Seas in the high resolution compared to the medium resolution. This is most likely due a better representation of the mean circulation in the studied region when using higher resolution. As the poleward propagation of ocean heat anomalies is considered to be a key source of climate predictability, we recommend that similar methodology presented herein should be performed on coupled climate models that are used for climate prediction.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Variability along the Atlantic water pathway in the forced Norwegian Earth System Model

et al. 2018

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“…Atmospheric forcing may be the biggest contributor to the sea ice loss (Serreze et al, ), but ocean heat storage and transport play an important role in certain regions (Carmack et al, ; Perovich & Richter‐Menge, ; Polyakov et al, ). For example, the decline and variability in winter sea ice cover north of Svalbard and in the Barents and Kara Seas is linked to an increased and warmer inflow of Atlantic Water (AW; Årthun et al, , ; Barton et al, ; Li et al, ; Onarheim et al, , , ). The Barents Sea experiences the fastest surface warming in the Arctic (Screen & Simmonds, ), and a recent study by Lind et al () found that the northern Barents Sea has transitioned from a cold Arctic to a warm Atlantic‐dominated regime.…”

Section: Introductionmentioning

confidence: 99%

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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“…Ocean heat content variability plays an important role in our climate system. In the Arctic‐Atlantic region, ocean heat anomalies have been shown to affect sea ice (e.g., Årthun et al, ; Yeager et al, ), marine ecosystems (Hátún et al, ), and potentially also continental climate (Årthun et al, ). There is, however, at present neither consensus nor any complete understanding of the mechanisms causing and maintaining such heat anomalies.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Ocean Heat Anomalies in the Norwegian Sea

et al. 2019

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Ocean heat content in the Norwegian Sea exhibits pronounced variability on interannual to decadal time scales. These ocean heat anomalies are known to influence Arctic sea ice extent, marine ecosystems, and continental climate. It nevertheless remains unknown to what extent such heat anomalies are produced locally within the Norwegian Sea, and to what extent the region is more of a passive receiver of anomalies formed elsewhere. A main practical challenge has been the lack of closed heat budget diagnostics. In order to address this issue, a regional heat budget is calculated for the Norwegian Sea using the ECCOv4 ocean state estimate—a dynamically and kinematically consistent model framework fitted to ocean observations for the period 1992–2015. The depth‐integrated Norwegian Sea heat budget shows that both ocean advection and air‐sea heat fluxes play an active role in the formation of interannual heat content anomalies. A spatial analysis of the individual heat budget terms shows that ocean advection is the primary contributor to heat content variability in the Atlantic domain of the Norwegian Sea. Anomalous heat advection furthermore depends on the strength of the Atlantic water inflow, which is related to large‐scale circulation changes in the subpolar North Atlantic. This result suggests a potential for predicting Norwegian Sea heat content based on upstream conditions. However, local surface forcing (air‐sea heat fluxes and Ekman forcing) within the Norwegian Sea substantially modifies the phase and amplitude of ocean heat anomalies along their poleward pathway, and, hence, acts to limit predictability.

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Skillful prediction of northern climate provided by the ocean

Cited by 107 publications

References 72 publications

Variability along the Atlantic water pathway in the forced Norwegian Earth System Model

Variability along the Atlantic water pathway in the forced Norwegian Earth System Model

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

Mechanisms of Ocean Heat Anomalies in the Norwegian Sea

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