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  • 1
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    PANGAEA
    In:  Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven
    Publication Date: 2023-03-16
    Keywords: ARK-XXVIII/2; AWI_PhyOce; BG2-1; Current direction; Current velocity, east-west; Current velocity, horizontal; Current velocity, north-south; DATE/TIME; DEPTH, water; Gear identification number; Mooring (long time); MOORY; North Greenland Sea; Physical Oceanography @ AWI; Polarstern; Pressure, water; PS85; Salinity; see comment for gear; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 1295784 data points
    Location Call Number Limitation Availability
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  • 2
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    PANGAEA
    In:  Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven
    Publication Date: 2023-03-16
    Keywords: AWI_PhyOce; BG2-2; Current direction; Current velocity, east-west; Current velocity, horizontal; Current velocity, north-south; DATE/TIME; DEPTH, water; Framstredet; Gear identification number; LA1508; Lance; Mooring (long time); MOORY; North Greenland Sea; Physical Oceanography @ AWI; Pressure, water; Salinity; see comment for gear; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 1114012 data points
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  • 3
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    PANGAEA
    In:  Supplement to: Tsubouchi, Takamasa; Bacon, Sheldon; Aksenov, Yevgeny; Naveira Garabato, Alberto C; Beszczynska-Möller, Agnieszka; Hansen, Edmond H; de Steur, Laura; Curry, Beth; Lee, Craig M (2018): The Arctic Ocean seasonal cycles of heat and freshwater fluxes: observation-based inverse estimates. Journal of Physical Oceanography, https://doi.org/10.1175/JPO-D-17-0239.1
    Publication Date: 2024-03-02
    Description: This paper presents the first estimate of the seasonal cycle of ocean and sea ice heat and freshwater (FW) fluxes around the Arctic Ocean boundary. The ocean transports are estimated primarily using 138 moored instruments deployed in September 2005 – August 2006 across the four main Arctic gateways: Davis, Fram and Bering Straits, and the Barents Sea Opening (BSO). Sea ice transports are estimated from a sea ice assimilation product. Monthly velocity fields are calculated with a box inverse model that enforces mass and salt conservation. The volume transports in the four gateways in the period (annual mean ± 1 standard deviation) are -2.1±0.7 Sv in Davis Strait, -1.1±1.2 Sv in Fram Strait, 2.3±1.2 Sv in BSO and 0.7±0.7 Sv Bering Strait (1 Sv = 10^{6} m^ {3} s^{-1}). The resulting ocean and sea ice heat and FW fluxes are 175±48 TW and 204±85 mSv, respectively. These boundary fluxes accurately represent the annual means of the relevant surface fluxes. The ocean heat transport variability derives from velocity variability in the Atlantic Water layer and temperature variability in the upper part of the water column. The ocean FW transport variability is dominated by Bering Strait velocity variability. The net water mass transformation in the Arctic entails a freshening and cooling of inflowing waters by 0.62±0.23 in salinity and 3.74±0.76°C in temperature, respectively, and a reduction in density by 0.23±0.20 kg m^{-3}. The boundary heat and FW fluxes provide a benchmark data set for the validation of numerical models and atmospheric re-analysis products.
    Keywords: Arctic; AWI_PhyOce; pan-Arctic; Physical Oceanography @ AWI
    Type: Dataset
    Format: application/zip, 102 MBytes
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  • 4
    Publication Date: 2024-03-02
    Description: This dataset provides 68 months time series of the Arctic ocean heat and FW transports from October 2004 to May 2010. They are estimated based on large amount of mooring data (around 1,000 moored instrument records) in the Arctic main gateways (Davis Strait, Fram Strait, Barents Sea Opening and Bering Strait) using box inverse model method as described in Tsubouchi et al. (2018). Thus, this dataset quantifies inter-annual variability of ocean volume, heat and FW transports. In the heat transport, we find maxima (169 TW) in 2004-2005 and minima (136 TW) in 2007-2008. The size of inter-annual variabilities accounts to 11% in total ocean transport. In the FW transport, we find maxima (127 mSv) in 2005-2006 and minima (67 mSv) in 2007-2008. The size of inter-annual variability accounts to 30% in total ocean FW transport. The quantified ocean transports and associated water mass transformation served as a bench mark dataset to validate various general ocean circulation models.
    Keywords: Arctic Ocean heat transports; Comment; Comment 2 (continued); File content; File format; File name; File size; freshwater transports; Uniform resource locator/link to file
    Type: Dataset
    Format: text/tab-separated-values, 418 data points
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  • 5
    Publication Date: 2021-02-08
    Description: Deep convection is a key process in the Atlantic Meridional Overturning Circulation, but because it acts at small scales, it remains poorly resolved by climate models. The occurrence of deep convection depends on weak initial stratification and strong surface buoyancy forcing, conditions that are satisfied in only a few ocean basins. In 2014, one of the Ocean Observatories Initiative (OOI) global arrays was installed close to the Central Irminger Sea (CIS) and the Long-term Ocean Circulation Observations (LOCO) moorings in the central Irminger Sea. These programs’ six moorings are located in the center of an area of deep convection and are distributed within a 50 km radius, thus offering detailed insight into spatial differences during the strong convection events that occurred during the winters of 2014/2015 and 2015/2016. Deep mixed layers, down to approximately 1,600 m, formed during both winters. The properties of the convectively renewed water mass at each mooring converge to a common temperature and salinity before restratification sets in at the end of winter. The largest differences in onset (or timing) of convection and restratification are seen between the northernmost and southernmost moorings. High-resolution atmospheric reanalysis data show there is higher atmospheric forcing at the northernmost mooring due to a more favorable position with respect to the Greenland tip jet. Nevertheless, earlier onset, and more continuous cooling and deepening of mixed layers, occurs at the southernmost mooring, while convection at the northern mooring is frequently interrupted by warm events. We propose that these warm events are associated with eddies and filaments originating from the Irminger Current off the coast of Greenland and that convection further south benefits from cold inflow from the southwest.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 6
  • 7
    Publication Date: 2024-04-08
    Description: For decades oceanographers have understood the Atlantic meridional overturning circulation (AMOC) to be primarily driven by changes in the production of deep-water formation in the subpolar and subarctic North Atlantic. Indeed, current Intergovernmental Panel on Climate Change (IPCC) projections of an AMOC slowdown in the twenty-first century based on climate models are attributed to the inhibition of deep convection in the North Atlantic. However, observational evidence for this linkage has been elusive: there has been no clear demonstration of AMOC variability in response to changes in deep-water formation. The motivation for understanding this linkage is compelling, since the overturning circulation has been shown to sequester heat and anthropogenic carbon in the deep ocean. Furthermore, AMOC variability is expected to impact this sequestration as well as have consequences for regional and global climates through its effect on the poleward transport of warm water. Motivated by the need for a mechanistic understanding of the AMOC, an international community has assembled an observing system, Overturning in the Subpolar North Atlantic Program (OSNAP), to provide a continuous record of the transbasin fluxes of heat, mass, and freshwater, and to link that record to convective activity and water mass transformation at high latitudes. OSNAP, in conjunction with the Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array (RAPID–MOCHA) at 26°N and other observational elements, will provide a comprehensive measure of the three-dimensional AMOC and an understanding of what drives its variability. The OSNAP observing system was fully deployed in the summer of 2014, and the first OSNAP data products are expected in the fall of 2017.
    Type: Article , PeerReviewed
    Format: text
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  • 8
    Publication Date: 2016-11-29
    Description: Large freshwater anomalies clearly exist in the Arctic Ocean. For example, liquid freshwater has accumulated in the Beaufort Gyre in the decade of the 2000s compared to 1980-2000, with an extra ≈ 5000 km3 — about 25% — being stored. The sources of freshwater to the Arctic from precipitation and runoff have increased between these periods (most of the evidence comes from models). Despite flux increases from 2001 to 2011, it is uncertain if the marine freshwater source through Bering Strait for the 2000s has changed, as observations in the 1980s and 1990s are incomplete. The marine freshwater fluxes draining the Arctic through Fram and Davis straits are also insignificantly different. In this way, the balance of sources and sinks of freshwater to the Arctic, Canadian Arctic Archipelago (CAA), and Baffin Bay shifted to about 1200 ± 730 km3 yr− 1 freshening the region, on average, during the 2000s. The observed accumulation of liquid freshwater is consistent with this increased supply and the loss of freshwater from sea ice. Coupled climate models project continued freshening of the Arctic during the 21st century, with a total gain of about 50,000 km3 for the Arctic, CAA, and Baffin Bay (an increase of about 50%) by 2100. Understanding of the mechanisms controlling freshwater emphasizes the importance of Arctic surface winds, in addition to the sources of freshwater. The wind can modify the storage, release, and pathways of freshwater on timescales of O(1-10) months. Discharges of excess freshwater through Fram or Davis straits appear possible, triggered by changes in the wind, but are hard to predict. Continued measurement of the fluxes and storage of freshwater is needed to observe changes such as these.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Wiley
    In:  EPIC3Journal of Geophysical Research-Oceans, Wiley, 122(5), pp. 4004-4020, ISSN: 0148-0227
    Publication Date: 2018-01-02
    Description: Nioghalvfjerdsfjorden Glacier (79NG) is the largest of three marine-terminating outlet glaciers draining the Northeast Greenland Ice Stream. To understand how Atlantic waters supply waters in the cavity beneath the floating 79NG, we analyze historic and recent bathymetric, hydrographic, and velocity observations obtained on the Northeast Greenland continental shelf. The bathymetry is characterized by a trough system, consisting of the Westwind Trough and the Norske Trough in the northern and southern part of the continental shelf, respectively. Atlantic waters recirculating in Fram Strait cross the shelf break and enter the trough system at its southeastern inlet toward the inner shelf. Warm Atlantic Intermediate Water (AIW) present below 200 m in the Norske Trough shows large contributions of the recirculating Atlantic water. We found that the bathymetry is sufficiently deep to provide a direct subsurface pathway for warm AIW between the shelf break and the 79NG cavity via the Norske Trough. Likewise, based on the hydrographic data, we show that the Norske Trough supplies AIW warmer than 1°C to the 79NG, which is not present in the Westwind Trough. Our moored and lowered velocity measurements indicate that a boundary current carries warm AIW along the northeastern slope of Norske Trough toward the 79NG. We suggest that anomalies in Atlantic water temperatures in Fram Strait could reach 79NG within less than 1.5 years, thereby modifying the glacier's basal melt rates.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 93-109, doi:10.1002/2016JC012106.
    Description: Liquid freshwater transports of the shelfbreak East Greenland Current (EGC) and the separated EGC are determined from mooring records from the Kögur section north of Denmark Strait between August 2011 and July 2012. The 11 month mean freshwater transport (FWT), relative to a salinity of 34.8, was 65 ± 11 mSv to the south. Approximately 70% of this was associated with the shelfbreak EGC and the remaining 30% with the separated EGC. Very large southward FWT ranging from 160 mSv to 120 mSv was observed from September to mid-October 2011 and was foremost due to anomalously low upper-layer salinities. The FWT may, however, be underestimated by approximately 5 mSv due to sampling biases in the upper ocean. The FWT on the Greenland shelf was estimated using additional inshore moorings deployed from 2012 to 2014. While the annual mean ranged from nearly zero during the first year to 18 mSv to the south during the second year, synoptically the FWT on the shelf can be significant. Furthermore, an anomalous event in autumn 2011 caused the shelfbreak EGC to reverse, leading to a large reduction in FWT. This reversed circulation was due to the passage of a large, 100 km wide anticyclone originating upstream from the shelfbreak. The late summer FWT of −131 mSv is 150% larger than earlier estimates based on sections in the late-1990s and early-2000s. This increase is likely the result of enhanced freshwater flux from the Arctic Ocean to the Nordic Seas during the early 2010s.
    Description: European Union Seventh Framework Programme Grant Numbers: (FP7 2007–2013), 308299; US National Science Foundation Grant Number: OCE-0959381
    Description: 2017-07-10
    Keywords: Freshwater ; East Greenland Current ; Mooring observations ; Time series
    Repository Name: Woods Hole Open Access Server
    Type: Article
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