Topographic Influence on Baroclinic Instability and the Mesoscale Eddy Field in the Northern North Atlantic Ocean and the Nordic Seas

Trodahl, Marta; Isachsen, Pål Erik

doi:10.1175/jpo-d-17-0220.1

Cited by 37 publications

(52 citation statements)

References 49 publications

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“…Similar to other parts of the Atlantic (Fratantoni, 2001;McWilliams, 1985), dynamic instability of the mean flows is found to be one of the leading mechanisms of mesoscale eddy generation in the Nordic Seas (Ghaffari et al, 2018;Hattermann et al, 2016;Johannessen et al, 1987;Trodahl & Isachsen, 2018;von Appen et al, 2016). In particular, the above-mentioned eastward increase of the EKE in the Fram Strait goes well with a much higher probability for the development of baroclinic instability along the eastern margin (Trodahl & Isachsen, 2018). At the EGC, the baroclinic instability is inhibited down to the latitude of Jan Mayen.…”

Section: Introductionmentioning

confidence: 66%

“…In some studies, barotropic instability is also considered to add to the generation of eddies along the WSC and some sections of the Norwegian Atlantic Slope Current (NwASC) (Ghaffari et al, 2018;Trodahl & Isachsen, 2018). Along the ice edge, where baroclinic and barotropic instability is relatively inefficient (Trodahl & Isachsen, 2018), alternative mechanisms of eddy generation are an interaction of the EGC with rough bottom topography (Johannessen et al, 1987) and an instability of tidal-frequency shelf waves, trapped by the topographic slope (Nilsen et al, 2006). The observed relatively small dominant wavelengths of such waves along the WSC suggest this latter mechanism to generate only relatively small eddies, with radii of 5-10 km.…”

Section: Introductionmentioning

confidence: 99%

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Eddies in the North Greenland Sea and Fram Strait From Satellite Altimetry, SAR and High‐Resolution Model Data

et al. 2020

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In this study, we investigate eddy dynamics in the northern Greenland Sea and the Fram Strait using AVISO altimetry, spaceborne synthetic aperture radar (SAR), and Finite Element Sea ice‐Ocean Model (FESOM) high‐resolution numerical model data. In the region, eddies are thought to play an important role in the redistribution of the warmer and saltier Atlantic Water between the Arctic Ocean and the areas of deep convection in the central Greenland Sea. We found that eddies detected in AVISO and in SAR form two complementary data sets of large mesoscale eddies (with typical radii of 30–50 km) and of small mesoscale/submesoscale eddies (with typical radii of 1–5 km and not exceeding 30 km), respectively. For large mesoscale eddies, the number of cyclones and anticyclones is approximately the same, while for submesoscale eddies, cyclones are strongly dominating. The limitations and possible biases in each of the data sets are discussed and cross‐validated against FESOM results. It is noted that the most energetic eddies are concentrated along the major currents and in the northern part of the region. Eddy translations follow the mean currents in their overall cyclonic circulation around the northern Greenland Sea. A convergence of the eddies toward the Nordbukta area is detected. On seasonal time scale, a higher number of more intense mesoscale eddies is observed during winter, associated with a quasi‐simultaneous intensification of the mean currents. Model results also show an increase in the number of small eddies in spring‐early summer attributed to the decay of large eddies, while in late autumn, the opposite tendency suggests eddy merger.

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Section: Introductionmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Eddies in the North Greenland Sea and Fram Strait From Satellite Altimetry, SAR and High‐Resolution Model Data

et al. 2020

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“…Both models consist of 35 vertical layers and are stored as daily averages. This temporal resolution is sufficient to resolve the mesoscale and submesoscale processes (Isachsen, ; Trodahl & Isachsen, ). The models also span similar time periods.…”

Section: Methodsmentioning

confidence: 99%

“…Runoff from primary rivers are supplied by monthly climatologies. The 4-km model was validated and analyzed in Trodahl and Isachsen (2018).…”

Section: Eulerian Calculationsmentioning

confidence: 99%

Lateral Heat Transport in the Lofoten Basin: Near‐Surface Pathways and Subsurface Exchange

et al. 2019

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The Lofoten Basin in the Nordic Seas plays a central role in the Atlantic overturning circulation by acting as a reservoir for the warm and saline Atlantic Water flow toward the Arctic Ocean. The mass and heat exchange between Atlantic Water and the Lofoten Basin impacts the water mass transformations and the surface heat loss, but the processes governing this exchange are not well understood or quantified. Here we study the circulation in the Nordic Seas and the heat transport in the Lofoten Basin using a combination of Lagrangian and Eulerian methods. We analyze the trajectories of about 150 surface drifters, augmented with a set of about 47,000 surface trajectories calculated using the output from a regional numerical simulation, to investigate the drifter pathways and their exchange with the Lofoten Basin. The drifters reveal that water parcels with long residence time inside the basin contribute substantially to the heat loss and typically enter from south across the outer rim of the Vøring Plateau and, to some extent from east, from the eastern branch of the Norwegian Atlantic Current. The main contributors to the lateral heat transport to the Lofoten Basin are the near‐surface heat transport by the mean flow in the southern sector of the basin and the subsurface eddy fluxes from the Lofoten Escarpment in the east.

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“…Based on the numerical model topography, c 5 0.004 is used for the western basin, where the topographic slope is constant. The choice of c in the eastern basin is not straightforward, as the lower growth rate predicted by the modified Eady theory cannot explain the observed enhanced eddy activity near the steep topographic slope (see discussion in, e.g., Trodahl and Isachsen 2018). Here, we follow the study of Bracco et al (2008) who suggested that a very steep topographic slope can be seen as a vertical wall.…”

Section: B a Conceptual Model With One Basin And A Single Boundary Cmentioning

confidence: 96%

The Contrasting Dynamics of the Buoyancy-Forced Lofoten and Greenland Basins

Ypma

Spall

Lambert

et al. 2020

Journal of Physical Oceanography

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The Nordic seas are commonly described as a single basin to investigate their dynamics and sensitivity to environmental changes when using a theoretical framework. Here, we introduce a conceptual model for a two-basin marginal sea that better represents the Nordic seas geometry. In our conceptual model, the marginal sea is characterized by both a cyclonic boundary current and a front current as a result of different hydrographic properties east and west of the midocean ridge. The theory is compared to idealized model simulations and shows good agreement over a wide range of parameter settings, indicating that the physics in the two-basin marginal sea is well captured by the conceptual model. The balances between the atmospheric buoyancy forcing and the lateral eddy heat fluxes from the boundary current and the front current differ between the Lofoten and the Greenland Basins, since the Lofoten Basin is more strongly eddy dominated. Results show that this asymmetric sensitivity leads to opposing responses depending on the strength of the atmospheric buoyancy forcing. Additionally, the front current plays an essential role for the heat and volume budget of the two basins, by providing an additional pathway for heat toward the interior of both basins via lateral eddy heat fluxes. The variability of the temperature difference between east and west influences the strength of the different flow branches through the marginal sea and provides a dynamical explanation for the observed correlation between the front current and the slope current of the Norwegian Atlantic Current in the Nordic seas.

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Topographic Influence on Baroclinic Instability and the Mesoscale Eddy Field in the Northern North Atlantic Ocean and the Nordic Seas

Cited by 37 publications

References 49 publications

Eddies in the North Greenland Sea and Fram Strait From Satellite Altimetry, SAR and High‐Resolution Model Data

Eddies in the North Greenland Sea and Fram Strait From Satellite Altimetry, SAR and High‐Resolution Model Data

Lateral Heat Transport in the Lofoten Basin: Near‐Surface Pathways and Subsurface Exchange

The Contrasting Dynamics of the Buoyancy-Forced Lofoten and Greenland Basins

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