Water column structure and statistics of Denmark Strait Overflow Water cyclones

Appen, Wilken-Jon von; Pickart, Robert S.; Brink, Kenneth H.; Haine, Thomas W. N.

doi:10.1016/j.dsr.2013.10.007

Cited by 33 publications

(75 citation statements)

References 34 publications

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“…9), two regions of enhanced EKE alt were revealed: along the shelf break south of 708N and just downstream of the sill. The latter maximum likely results from generation of cyclones or intensification of existing cyclones south of Denmark Strait as the overflow plume descends the continental slope (Bruce 1995;Spall and Price 1998;von Appen et al 2014). The average EKE alt for the 9 years of satellite data in the vicinity of the mooring array was similar to the values estimated from the Kögur observations during October 2011 (even though the mooring-based estimate was calculated from the time series at 100 m and the satellite measurements represent surface conditions).…”

Section: ) Estimate Of Eke From Satellite Altimetry Datasupporting

confidence: 65%

“…However, barotropic instability could also play a role during periods of strong horizontal velocity gradients, although our data are not conclusive in this regard. We further suggest that eddies formed by baroclinic instability in the shelfbreak EGC may be one of the sources of the variability observed at the Denmark Strait sill and that the substantial short-term variability previously documented at the sill von Appen et al 2017) and across the Kögur section (Harden et al 2016) is reflected by the high values of EKE.…”

Section: Summary and Discussionmentioning

confidence: 94%

“…A similar method for estimating EKE alt from satellite altimetry was used by von Appen et al (2016) comparable magnitude to our August to October values. Bulczak et al (2015) used sea surface height measurements from Envisat similar to our estimates to compare EKE alt from summer and winter across the entire Nordic Seas.…”

Section: ) Estimate Of Eke From Satellite Altimetry Datamentioning

confidence: 99%

“…Smith (1976) identified oscillations in the flow through Denmark Strait on time scales of 2 days in current meter data and attributed this variability to baroclinic instability of the overflow. Recently, two features have been identified as the dominant sources of mesoscale variability at the Denmark Strait sill: boluses and pulses von Appen et al 2017). The boluses are large lenses of weakly stratified overflow water associated with a modest strengthening of the flow.…”

Section: Introductionmentioning

confidence: 99%

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Structure and Variability of the Shelfbreak East Greenland Current North of Denmark Strait

Håvik

Våge

Pickart

et al. 2017

Journal of Physical Oceanography

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Data from a mooring array deployed north of Denmark Strait from September 2011 to August 2012 are used to investigate the structure and variability of the shelfbreak East Greenland Current (EGC). The shelfbreak EGC is a surface-intensified current situated just offshore of the east Greenland shelf break flowing southward through Denmark Strait. This study identified two dominant spatial modes of variability within the current: a pulsing mode and a meandering mode, both of which were most pronounced in fall and winter. A particularly energetic event in November 2011 was related to a reversal of the current for nearly a month. In addition to the seasonal signal, the current was associated with periods of enhanced eddy kinetic energy and increased variability on shorter time scales. The data indicate that the current is, for the most part, barotropically stable but subject to baroclinic instability from September to March. By contrast, in summer the current is mainly confined to the shelf break with decreased eddy kinetic energy and minimal baroclinic conversion. No other region of the Nordic Seas displays higher levels of eddy kinetic energy than the shelfbreak EGC north of Denmark Strait during fall. This appears to be due to the large velocity variability on mesoscale time scales generated by the instabilities. The mesoscale variability documented here may be a source of the variability observed at the Denmark Strait sill.

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Section: ) Estimate Of Eke From Satellite Altimetry Datasupporting

confidence: 65%

Section: Summary and Discussionmentioning

confidence: 94%

Section: ) Estimate Of Eke From Satellite Altimetry Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure and Variability of the Shelfbreak East Greenland Current North of Denmark Strait

Håvik

Våge

Pickart

et al. 2017

Journal of Physical Oceanography

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“…The cyclones may have diameters of 20–100 km and migrate downstream at speeds of 20–30 cm/s, remaining largely trapped within the EGIC, but with a slight downhill component (Bruce, ; Krauss, ; Krauss & Kase, ). At 65°N the separation time between cyclones is between 0 and 8 days (average of 2.1 days; von Appen et al, ). Further south at Cape Farewell, cyclonic eddies in water depths of 1,500–2,500 m have been observed (Krauss, ).…”

Section: Discussionmentioning

confidence: 99%

Transport Variability of the Irminger Sea Deep Western Boundary Current From a Mooring Array

et al. 2019

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The Deep Western Boundary Current in the subpolar North Atlantic is the lower limb of the Atlantic Meridional Overturning Circulation and a key component of the global climate system. Here, a mooring array deployed at 60°N in the Irminger Sea, between 2014 and 2016, provides the longest continuous record of total Deep Western Boundary Current volume transport at this latitude. The 1.8‐year averaged transport of water denser than σθ = 27.8 kg/m3 was −10.8 ± 4.9 Sv (mean ± 1 std; 1 Sv = 106 m3/s). Of this total, we find −4.1 ± 1.4 Sv within the densest layer (σθ > 27.88 kg/m3) that originated from the Denmark Strait Overflow. The lighter North East Atlantic Deep Water layer (σθ = 27.8–27.88 kg/m3) carries −6.5 ± 7.7 Sv. The variability in transport ranges between 2 and 65 days. There is a distinct shift from high to low frequency with distance from the East Greenland slope. High‐frequency fluctuations (2–8 days) close to the continental slope are likely associated with topographic Rossby waves and/or cyclonic eddies. Here, perturbations in layer thickness make a significant (20–60%) contribution to transport variability. In deeper water, toward the center of the Irminger Basin, transport variance at 55 days dominates. Our results suggest that there has been a 1.8 Sv increase in total transport since 2005–2006, but this difference can be accounted for by a range of methodological and data limitation biases.

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Extreme cooling and dense water formation estimates in open and coastal regions of the Adriatic Sea during the winter of 2012

Janeković

Mihanović

Vilibić

et al. 2014

J. Geophys. Res. Oceans

107

111

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Generation of dense waters in the Adriatic Sea during an extreme cooling event in the winter of 2012, including its preconditioning and spreading phases, have been investigated using the one-way coupled ROMS and the ALADIN/HR modeling system. Both climatological and real river fluxes are used in the simulations. Aside from the ''convenient'' dense water formation areas located at the northernmost Adriatic shelf, we found that a similar amount of dense water, with slightly lower density, was formed in the eastern and deeper Adriatic coastal area, which was subjected to extreme heat losses (up to 2000 W/m 2 ) during peak cooling periods. This part of the Adriatic has been known for extreme cooling during wintertime bora outbreaks; nevertheless, no ocean model study has previously reproduced dense water formation in this area. The most likely reason for that was an overestimate of river discharges introduced to ocean models. From newly available data, we estimated that the contribution of eastern Adriatic rivers between the Neretva River and Rijeka Bay is more than six times lower than what has been previously documented. Transport of dense water toward the middle Adriatic had a peak value of about 0.6 Sv, while the speed of initial bottom density current surpassed 40-50 cm/s, which is several times faster than past events. Different pathways of the dense water toward the middle and south Adriatic depressions have also been documented. The contribution of the eastern coastal Adriatic area to the overall north Adriatic dense water formation has been quantified and discussed for average and low freshwater load conditions, indicating that this part of the Adriatic is a common place for dense water generation.

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Water column structure and statistics of Denmark Strait Overflow Water cyclones

Cited by 33 publications

References 34 publications

Structure and Variability of the Shelfbreak East Greenland Current North of Denmark Strait

Structure and Variability of the Shelfbreak East Greenland Current North of Denmark Strait

Transport Variability of the Irminger Sea Deep Western Boundary Current From a Mooring Array

Extreme cooling and dense water formation estimates in open and coastal regions of the Adriatic Sea during the winter of 2012

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