Freshwater Export from the Arctic Ocean and Its Downstream Effect on Labrador Sea Deep Convection in a High-resolution Numerical Model PDF Download
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Author: Timothy P. McGeehan
Publisher:
ISBN:
Category : Arctic Ocean
Languages : en
Pages : 185
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Book Description
The Labrador Sea is one of the only known locations of deep open ocean convection, a process determined to play a significant role in regulating global thermohaline circulation and climate. The main hypothesis of this study is that low salinity water from the Arctic Ocean, particularly outflow through the Canadian Arctic Archipelago (CAA), may affect Labrador Sea deep convection. To address it, output from a pan-Arctic high-resolution coupled ice-ocean model was examined. Volume and freshwater fluxes through the CAA for 1979-2004 were found in good agreement with the observations. Further analyses suggest that the flow through the major CAA channels depends on the sea surface height gradient between the Arctic Ocean and northern Baffin Bay. Freshwater flux anomalies entering the Labrador Sea through Davis Strait do not immediately affect deep convection. Instead, eddies and sea ice acting on shorter time scales can move freshwater to locations of active convection and halt the process, which underscores the importance of high-resolution. Also, changing ice conditions revealed the Northwest Passage was a possible shipping route in three summers. Finally, preliminary results from an eddyresolving model configuration suggest that many of the shortcomings in this model may be rectified with higher spatial resolution.
Author: Timothy P. McGeehan
Publisher:
ISBN:
Category : Arctic Ocean
Languages : en
Pages : 185
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Book Description
The Labrador Sea is one of the only known locations of deep open ocean convection, a process determined to play a significant role in regulating global thermohaline circulation and climate. The main hypothesis of this study is that low salinity water from the Arctic Ocean, particularly outflow through the Canadian Arctic Archipelago (CAA), may affect Labrador Sea deep convection. To address it, output from a pan-Arctic high-resolution coupled ice-ocean model was examined. Volume and freshwater fluxes through the CAA for 1979-2004 were found in good agreement with the observations. Further analyses suggest that the flow through the major CAA channels depends on the sea surface height gradient between the Arctic Ocean and northern Baffin Bay. Freshwater flux anomalies entering the Labrador Sea through Davis Strait do not immediately affect deep convection. Instead, eddies and sea ice acting on shorter time scales can move freshwater to locations of active convection and halt the process, which underscores the importance of high-resolution. Also, changing ice conditions revealed the Northwest Passage was a possible shipping route in three summers. Finally, preliminary results from an eddyresolving model configuration suggest that many of the shortcomings in this model may be rectified with higher spatial resolution.
Author: Marine Decuypère
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"A recent study links an increase in the horizontal resolution of ocean models to improved representations of Arctic sea-ice and Ocean Heat Transport (OHT, Docquier et al., 2019). Here, the impact of horizontal resolution on meridional OHT, sea-ice natural variability and response to climate change is investigated over a broader range of spatial resolutions, using the GFDL CM2-O climate model suite (1°, 1/4°, and 1/10°) in both preindustrial control and climate change simulations. Results show a direct link between OHT and sea-ice extent (SIE) in the Arctic. This link, however, is not monotonic with spatial resolution contrary to findings by Docquier et al. (2019). While OHT increases and SIE decreases from the Low to the Medium resolution models, the reverse is true from the Medium to the High resolution models. Differences in OHT and SIE between the three models mostly arise from the preindustrial state. As the spatial resolution increases, the Irminger Current - recirculating waters around the southern tip of Greenland - is favored at the expense of the North Atlantic Drift - bringing water in the Arctic through Fram Strait and the Barents Sea Opening (BSO). This rerouting of water to the Western side of Greenland results in less heat delivered to the Arctic in the High resolution model than in its Medium counterpart. As a result, the Medium resolution model is in best agreement with observed SIE and OHT in the BSO and Fram Strait - the Bering Strait OHT is smaller than observed in all models. Concurrent with the change in the partitioning in volume is a gradual change in deep convection centers from the Greenland-Irminger-Norwegian (GIN) Seas in the Low resolution model to the Labrador Sea in the High resolution model. Results strongly suggest a role for the deep convection in the North Atlantic on the OHT into the Arctic"--
Author: Robert R. Dickson
Publisher: Springer Science & Business Media
ISBN: 1402067747
Category : Science
Languages : en
Pages : 728
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Book Description
We are only now beginning to understand the climatic impact of the remarkable events that are now occurring in subarctic waters. Researchers, however, have yet to agree upon a predictive model that links change in our northern seas to climate. This volume brings together the body of evidence needed to develop climate models that quantify the ocean exchanges through subarctic seas, measure their variability, and gauge their impact on climate.
Author: David N. Thomas
Publisher: John Wiley & Sons
ISBN: 9781444317152
Category : Technology & Engineering
Languages : en
Pages : 641
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Book Description
As the Arctic perennial sea ice continues to disappear at an alarming rate, a full understanding of sea ice as a crucial global ecosystem, and the effects of its loss is vital for all those working with and studying global climate change. Building on the success of the previous edition, the second edition of Sea Ice, now much expanded and in full colour throughout, includes six completely new chapters with complete revisions of all the chapters included from the first edition. The Editors, Professor David Thomas and Dr Gerhard Dieckmann have once again drawn together an extremely impressive group of internationally respected contributing authors, ensuring a comprehensive worldwide coverage of this incredibly important topic. Sea Ice, second edition, is an essential purchase for oceanographers and marine scientists, environmental scientists, biologists, geochemists and geologists. All those involved in the study of global climate change will find this book to contain a wealth of important information. All libraries in universities and research establishments where these subjects are studied and taught will need multiple copies of this book on their shelves. truly multidisciplinary approach world leading authors and editors international in scope, covering both Arctic and Antarctic work of vital interest to all those involved in global warming and climate change research highly illustrated full colour book with colour images throughout
Author: Theresa Jayne Morrison
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The increased presence of warm Atlantic water on the Greenland continental shelf and within glacial fjords has been connected to the accelerated melting of the Greenland Ice Sheet, particularly in the southwest and southeast continental shelf regions. Meltwater is transported into the Labrador Sea where it may disrupt deep convection, a process that has been linked to the variability of the Atlantic Meridional Overturning Circulation (AMOC). To study the transport of heat onto the continental shelf and freshwater into the Labrador Sea, we use coupled ocean/sea-ice simulations with horizontal resolutions that permit or resolve mesoscale eddies. We compare the on shelf transport of heat in two mesoscale eddy-permitting simulations. In both simulations, the region of greatest heat flux onto the shelf is southeast Greenland and south of the Denmark strait, where there is a seasonally persistent pattern of multi-day variability in the cross-shelf heat flux. This high-frequency variability is associated with Denmark Strait Overflow eddies propagating along the shelfbreak. Using mesoscale eddy-resolving simulations to compare the off-shelf transport of meltwater and impacts on the West Greenland Current, we find that vertically distributed meltwater results in an increase in total freshwater flux into the Labrador Sea. Eddy kinetic energy and baroclinic conversion in the West Greenland Current along the continental shelf break also increase with the addition of vertically distributed meltwater. Finally, we derive and test a box model to represent the mixing within fjords. This Fjord Box Model merges buoyant plume theory with the estuarine mixing that occurs along fjords. The Fjord Box Model provides a more realistic boundary condition for meltwater forcing in ocean models that cannot resolve fjords.
Author:
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Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 2
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Book Description
Author: Kara L. Lavender
Publisher:
ISBN:
Category : Ocean currents
Languages : en
Pages : 302
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Book Description
Author: Ian Gouverneur Fenty
Publisher:
ISBN:
Category :
Languages : en
Pages : 277
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Book Description
Sea ice (SI) and ocean variability in marginal polar and subpolar seas are closely coupled. SI variability in the Labrador Sea is of climatic interest because of its relationship to deep convection/mode water formation, carbon sequestration, and Northern Hemisphere atmospheric patterns. Historically, quantifying the link between the region's observed SI and oceanic variability has been limited due to in situ observation paucity and technical challenges associated with synthesizing ocean and SI observations with a three-dimensional time-evolving dynamically consistent numerical model. To elaborate upon the relationship between SI and ocean variability, a one year (1996- 1997) state estimate of the ocean and sea ice state in Labrador Sea and Baffin Bay is constructed and analyzed. The estimate is a synthesis of a regional coupled 32 km ocean and sea ice model with a suite of contemporary in situ and satellite hydrographic and SI data. The synthesis of SI data is made possible with the (novel) adjoint of a thermodynamic SI model. Model and data are made consistent, in a least-squares sense, by iteratively adjusting several control variables, such as ocean initial and lateral open boundary conditions and the atmospheric state, to minimize an uncertainty-weighted model-data misfit cost function. It is shown that the SI pack attains a state of quasi-equilibrium in mid-March during which net SI growth/melt approaches zero; newly-formed SI diverges from coastal areas and converges, via wind/ocean forcing, in the marginal ice zone (MIZ). It is further shown that SI converging in the MIZ is primarily ablated by turbulent ocean-SI enthalpy fluxes. The primary source of energy required for sustained MIZ ice ablation is revealed to be the sensible heat reservoir of the subtropical-origin subsurface waters. Enthalpy from the heat reservoir is entrained into the mixed layer via buoyancy loss-driven convective deepening and brought to the SI via vertical mixing. An analysis of ocean surface buoyancy fluxes reveals a critical role of low-salinity upper ocean anomalies for the advancement of SI seaward of the Arctic Water/Irminger Water thermohaline front. Anomalous low-salinity waters slow the rate of buoyancy loss-driven mixed layer deepening, shielding an advancing SI pack from the subsurface heat reservoir, and are conducive to a positive surface stratification enhancement feedback from SI meltwater release, both of which extend SI lifetimes. Preliminary analysis of two additional one-year state estimates (1992-1993, 2003-2004) suggests that interannual hydrographic variability provides a first-order explanation for SI maximum extent anomalies. Additional research on the mechanisms controlling the origin and distribution of upper ocean salinity anomalies is required to further understand observed SI variability in the northwest North Atlantic.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309054494
Category : Science
Languages : en
Pages : 645
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Book Description
This volume reflects the current state of scientific knowledge about natural climate variability on decade-to-century time scales. It covers a wide range of relevant subjects, including the characteristics of the atmosphere and ocean environments as well as the methods used to describe and analyze them, such as proxy data and numerical models. They clearly demonstrate the range, persistence, and magnitude of climate variability as represented by many different indicators. Not only do natural climate variations have important socioeconomic effects, but they must be better understood before possible anthropogenic effects (from greenhouse gas emissions, for instance) can be evaluated. A topical essay introduces each of the disciplines represented, providing the nonscientist with a perspective on the field and linking the papers to the larger issues in climate research. In its conclusions section, the book evaluates progress in the different areas and makes recommendations for the direction and conduct of future climate research. This book, while consisting of technical papers, is also accessible to the interested layperson.
