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  • 1
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    High-Frequency Variability in the Circulation and Hydrography of the Denmark Strait Overflow from a High-Resolution Numerical Model (2017)
    American Meteorological Society
    Details
    Publication Date: 2017-12-01
    Description: Initial results are presented from a yearlong, high-resolution (~2 km) numerical simulation covering the east Greenland shelf and the Iceland and Irminger Seas. The model hydrography and circulation in the vicinity of Denmark Strait show good agreement with available observational datasets. This study focuses on the variability of the Denmark Strait overflow (DSO) by detecting and characterizing boluses and pulses, which are the two dominant mesoscale features in the strait. The authors estimate that the yearly mean southward volume flux of the DSO is about 30% greater in the presence of boluses and pulses. On average, boluses (pulses) are 57.1 (27.5) h long, occur every 3.2 (5.5) days, and are more frequent during the summer (winter). Boluses (pulses) increase (decrease) the overflow cross-sectional area, and temperatures around the overflow interface are colder (warmer) by about 2.6°C (1.8°C). The lateral extent of the boluses is much greater than that of the pulses. In both cases the along-strait equatorward flow of dense water is enhanced but more so for pulses. The sea surface height (SSH) rises by 4–10 cm during boluses and by up to 5 cm during pulses. The SSH anomaly contours form a bowl (dome) during boluses (pulses), and the two features cross the strait with a slightly different orientation. The cross streamflow changes direction; boluses (pulses) are associated with veering (backing) of the horizontal current. The model indicates that boluses and pulses play a major role in controlling the variability of the DSO transport into the Irminger Sea.
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
    Published by American Meteorological Society
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  • 2
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    On the Nature of the Mesoscale Variability in Denmark Strait (2017)
    American Meteorological Society
    Details
    Publication Date: 2017-03-01
    Description: Time series data from a mooring in the center of Denmark Strait and a collection of shipboard hydrographic sections occupied across the sill are used to elucidate the mesoscale variability of the dense overflow water in the strait. Two dominant, reoccurring features are identified that are referred to as a bolus and a pulse. A bolus is a large, weakly stratified lens of overflow water associated with cyclonic rotation and a modest increase in along-stream speed of 0.1 m s−1. When a bolus passes through the strait the interface height of the overflow layer increases by 60 m, and the bottom temperature decreases by 0.4°C. By contrast, a pulse is characterized by anticyclonic rotation, a strong increase in along-stream speed of 〉0.25 m s−1, a decrease in interface height of 90 m, and no significant bottom temperature signal. It is estimated that, on average, boluses (pulses) pass through the strait every 3.4 (5.4) days with no seasonal signal to their frequency. Both features have the strongest along-stream signal in the overflow layer, while the strongest cross-stream velocities occur above the Denmark Strait overflow water (DSOW). In this sense neither feature can be characterized as a simple propagating eddy. Their dynamics appear to be similar to that ascribed to the mesoscale variability observed downstream in the deep western boundary current. Strong correlation of bottom temperatures between the mooring in Denmark Strait and a downstream array, together with a match in the frequency of occurrence of features at both locations, suggests a causal relationship between the mesoscale variability at the sill and that farther downstream.
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
    Published by American Meteorological Society
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  • 3
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    Frontogenesis and Variability in Denmark Strait and Its Influence on Overflow Water (2019)
    American Meteorological Society
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    Publication Date: 2019-07-01
    Description: A high-resolution numerical model, together with in situ and satellite observations, is used to explore the nature and dynamics of the dominant high-frequency (from one day to one week) variability in Denmark Strait. Mooring measurements in the center of the strait reveal that warm water “flooding events” occur, whereby the North Icelandic Irminger Current (NIIC) propagates offshore and advects subtropical-origin water northward through the deepest part of the sill. Two other types of mesoscale processes in Denmark Strait have been described previously in the literature, known as “boluses” and “pulses,” associated with a raising and lowering of the overflow water interface. Our measurements reveal that flooding events occur in conjunction with especially pronounced pulses. The model indicates that the NIIC hydrographic front is maintained by a balance between frontogenesis by the large-scale flow and frontolysis by baroclinic instability. Specifically, the temperature and salinity tendency equations demonstrate that the eddies act to relax the front, while the mean flow acts to sharpen it. Furthermore, the model reveals that the two dense water processes—boluses and pulses (and hence flooding events)—are dynamically related to each other and tied to the meandering of the hydrographic front in the strait. Our study thus provides a general framework for interpreting the short-time-scale variability of Denmark Strait Overflow Water entering the Irminger Sea.
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
    Published by American Meteorological Society
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  • 4
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    On the hydrography of Denmark Strait (2017)
    American Geophysical Union
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    Publication Date: 2017-01-01
    Print ISSN: 2169-9275
    Electronic ISSN: 2169-9291
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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  • 5
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    The East Greenland Spill Jet as an important component of the Atlantic Meridional Overturning Circulation (2014)
    Elsevier
    Details
    Publication Date: 2014-10-01
    Print ISSN: 0967-0637
    Electronic ISSN: 1879-0119
    Topics: Biology , Geosciences , Physics
    Published by Elsevier
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  • 6
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    The East Greenland Spill Jet as an important component of the Atlantic Meridional Overturning Circulation (2014)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 92 . pp. 75-84.
    Details
    Publication Date: 2019-07-10
    Description: Highlights: • Mooring observations show the East Greenland Spill Jet to be ubiquitous. • It is fed by classical DSOW in Denmark Strait, shelf water, and Irminger Sea water. • Its transport is similar to the classical DSOW plume. • It is the origin of a large fraction of the water in the Labrador Sea Water density range. Abstract: The recently discovered East Greenland Spill Jet is a bottom-intensified current on the upper continental slope south of Denmark Strait, transporting intermediate density water equatorward. Until now the Spill Jet has only been observed with limited summertime measurements from ships. Here we present the first year-round mooring observations demonstrating that the current is a ubiquitous feature with a volume transport similar to the well-known plume of Denmark Strait overflow water farther downslope. Using reverse particle tracking in a high-resolution numerical model, we investigate the upstream sources feeding the Spill Jet. Three main pathways are identified: particles flowing directly into the Spill Jet from the Denmark Strait sill; particles progressing southward on the East Greenland shelf that subsequently spill over the shelfbreak into the current; and ambient water from the Irminger Sea that gets entrained into the flow. The two Spill Jet pathways emanating from Denmark Strait are newly resolved, and long-term hydrographic data from the strait verifies that dense water is present far onto the Greenland shelf. Additional measurements near the southern tip of Greenland suggest that the Spill Jet ultimately merges with the deep portion of the shelfbreak current, originally thought to be a lateral circulation associated with the sub-polar gyre. Our study thus reveals a previously unrecognized significant component of the Atlantic Meridional Overturning Circulation that needs to be considered to understand fully the ocean׳s role in climate.
    Type: Article , PeerReviewed
    Format: text
    Format: video
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  • 7
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    On the Nature of the Mesoscale Variability in Denmark Strait (2017)
    In:  EPIC3Journal of Physical Oceanography, 47(3), pp. 567-582, ISSN: 0022-3670
    Details
    Publication Date: 2017-03-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
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    The East Greenland Spill Jet as an important component of the Atlantic Meridional Overturning Circulation (2014)
    PERGAMON-ELSEVIER SCIENCE LTD
    In:  EPIC3Deep-Sea Research Part I-Oceanographic Research Papers, PERGAMON-ELSEVIER SCIENCE LTD, 92, pp. 75-84, ISSN: 0967-0637
    Details
    Publication Date: 2014-08-18
    Description: The recently discovered East Greenland Spill Jet is a bottom-intensified current on the upper continental slope south of Denmark Strait, transporting intermediate density water equatorward. Until now the Spill Jet has only been observed with limited summertime measurements from ships. Here we present the first year-round mooring observations demonstrating that the current is a ubiquitous feature with a volume transport similar to the well-known plume of Denmark Strait overflow water farther downslope. Using reverse particle tracking in a high-resolution numerical model, we investigate the upstream sources feeding the Spill Jet. Three main pathways are identified: particles flowing directly into the Spill Jet from the Denmark Strait sill; particles progressing southward on the East Greenland shelf that subsequently spill over the shelfbreak into the current; and ambient water from the Irminger Sea that gets entrained into the flow. The two Spill Jet pathways emanating from Denmark Strait are newly resolved, and long-term hydrographic data from the strait verifies that dense water is present far onto the Greenland shelf. Additional measurements near the southern tip of Greenland suggest that the Spill Jet ultimately merges with the deep portion of the shelfbreak current, originally thought to be a lateral circulation associated with the sub-polar gyre. Our study thus reveals a previously unrecognized significant component of the Atlantic Meridional Overturning Circulation that needs to be considered to understand fully the ocean's role in climate.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Hydrographic structure of overflow water passing through the Denmark Strait (2015)
    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2015
    Description: Denmark Strait Overflow Water (DSOW) constitutes the densest portion of North Atlantic Deep Water, which feeds the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). As such, it is critical to understand how DSOW is transferred from the upstream basins in the Nordic Seas, across the Greenland-Scotland Ridge, and to the North Atlantic Ocean. The goal of this study is to characterize the hydrographic structure of the different DSOW constituents at the sill before the water descends into the Irminger Sea using temperature and salinity (T/S) data from 111 shipboard crossings in the vicinity of the sill, collected between 1990 and 2012. The individual realizations indicate that weakly stratified "boluses" of DSOW frequent the sill and contribute the densest water to the overflow. This study also characterizes the structure, size, and location of the boluses and relates them to the T/S modes found at the sill. Lastly, historical hydrographic data from the Nordic Seas are used to make inferences regarding the origin of the boluses.
    Description: Financial support for this work was provided by the National Science Foundation grant OCE-0959381.
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
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  • 10
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    The East Greenland Spill Jet as an important component of the Atlantic Meridional Overturning Circulation (2014)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 92 (2014): 75-84, doi:10.1016/j.dsr.2014.06.002.
    Description: The recently discovered East Greenland Spill Jet is a bottom-intensified current on the upper continental slope south of Denmark Strait, transporting intermediate density water equatorward. Until now the Spill Jet has only been observed with limited summertime measurements from ships. Here we present the first year-round mooring observations demonstrating that the current is a ubiquitous feature with a volume transport similar to the well-known plume of Denmark Strait overflow water farther downslope. Using reverse particle tracking in a high-resolution numerical model, we investigate the upstream sources feeding the Spill Jet. Three main pathways are identified: particles flowing directly into the Spill Jet from the Denmark Strait sill; particles progressing southward on the East Greenland shelf that subsequently spill over the shelfbreak into the current; and ambient water from the Irminger Sea that gets entrained into the flow. The two Spill Jet pathways emanating from Denmark Strait are newly resolved, and long-term hydrographic data from the strait verifies that dense water is present far onto the Greenland shelf. Additional measurements near the southern tip of Greenland suggest that the Spill Jet ultimately merges with the deep portion of the shelfbreak current, originally thought to be a lateral circulation associated with the sub-polar gyre. Our study thus reveals a previously unrecognized significant component of the Atlantic Meridional Overturning Circulation that needs to be considered to understand fully the ocean’s role in climate.
    Description: Support for this study was provided by the U.S. National Science Foundation (OCE-0726640, OCI-1088849, OCI-0904338), the German Federal Ministry of Education and Research (0F0651 D), and the Italian Ministry of University and Research through the RITMARE Flagship Project.
    Keywords: East Greenland Spill Jet ; Denmark Strait Overflow Water ; Atlantic meridional overturning circulation ; Shelf basin interaction
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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