On the hydrography of <scp>D</scp>enmark <scp>S</scp>trait

Mastropole, Dana; Pickart, Robert S.; Valdimarsson, Héðinn; Våge, Kjetil; Jochumsen, Kerstin; Girton, James B.

doi:10.1002/2016jc012007

Cited by 57 publications

(116 citation statements)

References 41 publications

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“…Finally, anticyclones coincide with an enhanced cross‐sectional flow toward Greenland within the overflow layer (Figure h). All of these anomalies in the composites of cyclones and anticyclones are consistent with the anomalies associated with boluses and pulses, respectively (Almansi et al, ; Mastropole et al, ; von Appen et al, ).…”

Section: Resultsmentioning

confidence: 99%

Evolution of Denmark Strait Overflow Cyclones and Their Relationship to Overflow Surges

Almansi

Haine

Gelderloos

et al. 2020

Geophysical Research Letters

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Mesoscale features present at the Denmark Strait sill regularly enhance the volume transport of the Denmark Strait overflow (DSO). They are important for the Atlantic Meridional Overturning Circulation and ultimately, for the global climate system. Using a realistic numerical model, we find new evidence of the causal relationship between overflow surges (i.e., mesoscale features associated with high‐transport events) and DSO cyclones observed downstream. Most of the cyclones form at the Denmark Strait sill during overflow surges and, because of potential vorticity conservation and stretching of the water column, grow as they move equatorward. A fraction of the cyclones form downstream of the sill, when anticyclonic vortices formed during high‐transport events start collapsing. Regardless of their formation mechanism, DSO cyclones weaken starting roughly 150 km downstream of the sill, and potential vorticity is only materially conserved during the growth phase.

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Section: Resultsmentioning

confidence: 99%

Evolution of Denmark Strait Overflow Cyclones and Their Relationship to Overflow Surges

Almansi

Haine

Gelderloos

et al. 2020

Geophysical Research Letters

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“…[] argue for 3.2 Sv as a long‐term average with no trend. While there is some very dense water (σ θ > 28.0) in the Denmark St. [ Mastropole et al ., ], is its supply great enough to increase the flux of water with σ θ > 27.8 by a factor 3 (from 3.2 to O(10) Sv)? Given this wide range of estimates and uncertainties on the one hand yet highly localized flow south both near the surface and at depth, it seems like a strong case could be made for a sustained monitoring program with a moored current array at depth with the Nuka Arctica ADCP covering the upper ocean using XCTDs in addition to Argo to fill in the upper ocean density field.…”

Section: Discussionmentioning

confidence: 98%

A direct estimate of poleward volume, heat, and freshwater fluxes at 59.5°N between Greenland and Scotland

et al. 2017

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The meridional overturning circulation (MOC) in the North Atlantic plays a major role in the transport of heat from low to high latitudes. In this study, we combine recent measurements of currents from the surface to >700 m from a shipboard acoustic Doppler current profiler with Argo profiles (to 2000 m) to estimate poleward volume, heat, and freshwater flux at 59.5°N between Greenland and Scotland. This is made possible thanks to the vessel Nuka Arctica that operates on a 3 week schedule between Greenland and Denmark. For the period late 2012 to early 2016, the deseasoned mean meridional overturning circulation reaches a 18.4 ± 3.4 Sv maximum at the σθ = 27.55 kg m−3 isopycnal, which varies in depth from near the surface in the western Irminger Sea to 1000 m in Rockall Trough. The total heat and freshwater fluxes across 59.5°N = 399 ± 74 TW and −0.20 ± 0.04 Sv, where the uncertainties are principally due to that of the MOC. Analysis of altimetric sea surface height variations along exactly the same route reveals a somewhat stronger geostrophic flow north during this period compared to the 23 year mean suggesting that for a long‐term mean the above flux estimates should be reduced slightly to 17.4 Sv, 377 TW, and −0.19 Sv, respectively, with the same estimate uncertainties. The ADCP program is ongoing.

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“…Eddies are one potential source of variability at the sill, and while cyclones and anticyclones are documented north and south of the sill from observations and models, they have not been clearly identified in the passage or at the sill (e.g., Bruce, 1995;Harden et al, 2016;Jungclaus et al, 2001;Krauss & Käse, 1998;Lundrigan & Demirov, 2019;Shi et al, 2001;Voet & Quadfasel, 2010). Recent observational and model studies describe the variability in terms of a background flow disturbed by boluses or pulses passing over the sill (Almansi et al, 2017;Mastropole et al, 2017;von Appen et al, 2017). Boluses are defined as cold, weakly stratified lenses that are accompanied by increased current speeds and a thickening of the plume.…”

Section: 1029/2019jc015273mentioning

confidence: 99%

“…Another important set of mesoscale features found at the DS sill are boluses and pulses (Almansi et al, 2017;Mastropole et al, 2017;von Appen et al, 2017). We use our data set to identify such phenomena and relate them to the occurrence of eddies.…”

Section: Boluses and Pulsesmentioning

confidence: 99%

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Mesoscale Eddies Observed at the Denmark Strait Sill

et al. 2019

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The Denmark Strait overflow is the major export route of dense water from the Arctic Mediterranean into the North Atlantic. At the Strait's shallow sill, the overflow is a bottom-intensified cold and dense plume, bound to the east by a thermal front formed with the warmer, northward flowing North Icelandic Irminger Current. More than two decades of observations at the sill show strong fluctuations of volume flux on daily time scales. To better understand the source of this variability, a five-mooring array was installed at the sill, capturing nearly 1 year of velocity and bottom temperature measurements at a high temporal and spatial resolution. Bottom temperature fluctuations that exceed 4 • C indicate a meandering of the front between the plume and the North Icelandic Irminger Current. Current vector rotation shows trains of alternating cyclones and anticyclones at the sill. An eddy crosses the sill every 3 to 6 days with a mean velocity of 0.4 m/s and a typical diameter of 30 to 40 km. The results suggest that anticyclones, with centers passing through the deepest part of the sill, may be responsible for periods of increased volume flux-also referred to as boluses and pulses in previous studies. Although the relationship between eddies, pulses, and boluses is still unclear, the results show that eddies are directly linked to fluctuations in the strength, thickness, and position of the overflow plume. Plain Language SummaryThe southward flow of dense water from the Arctic ocean plays a crucial role in global ocean circulation but is almost immediately constrained on its way south by a submarine ridge that connects Greenland, Iceland, the Faroe Islands, and Scotland. The southward flow is therefore forced to pass through several straits and up and over relatively shallow sills. Most of the flow passes over a sill in the Denmark Strait, located between Greenland and Iceland. In this study, we present observations from an array of instruments, which measure the southward flow as it passes over the Denmark Strait sill. The flow is characterised by trains of eddies (vortices), with an alternating sense of rotation; meaning a counterclockwise eddy is usually followed by a clockwise eddy. The eddies are 30 to 40 km wide and need about 1 day to pass over the sill. These eddies help to explain pronounced changes in the flow across the sill, as they can help either to speed up the flow or slow it down. The results of this study contribute to understanding mesoscale fluctuations, which influence local mixing processes and water mass transports.

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On the hydrography of Denmark Strait

Cited by 57 publications

References 41 publications

Evolution of Denmark Strait Overflow Cyclones and Their Relationship to Overflow Surges

Evolution of Denmark Strait Overflow Cyclones and Their Relationship to Overflow Surges

A direct estimate of poleward volume, heat, and freshwater fluxes at 59.5°N between Greenland and Scotland

Mesoscale Eddies Observed at the Denmark Strait Sill

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