Journal ArticleDOI
On the freshwater forcing and transport of the Atlantic thermohaline circulation
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In this article, it is argued that the freshwater loss to the atmosphere arises mainly in the subtropical South Atlantic and is balanced by northward freshwater transport in the wind-driven sub-tropical gyre, while the thermohaline circulation transports freshwater southward.Abstract:
The 'conveyor belt' circulation of the Atlantic Ocean transports large amounts of heat northward, acting as a heating system for the northern North Atlantic region. It is widely thought that this circulation is driven by atmospheric freshwater export from the Atlantic catchment region, and that it transports freshwater northward to balance the loss to the atmosphere. Using results from a simple conceptual model and a global circulation model, it is argued here that the freshwater loss to the atmosphere arises mainly in the subtropical South Atlantic and is balanced by northward freshwater transport in the wind-driven subtropical gyre, while the thermohaline circulation transports freshwater southward. It is further argued that the direction of freshwater transport is closely linked to the dynamical regime and stability of the 'conveyor belt': if its freshwater transport is indeed southward, then its flow is purely thermally driven and inhibited by the freshwater forcing. In this case the circulation is not far from Stommel's saddle-node bifurcation, and a circulation state without NADW formation would also be stable.read more
Citations
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Journal ArticleDOI
Constraints on future changes in climate and the hydrologic cycle
Myles R. Allen,William Ingram +1 more
TL;DR: It will be substantially harder to quantify the range of possible changes in the hydrologic cycle than in global-mean temperature, both because the observations are less complete and because the physical constraints are weaker.
Journal ArticleDOI
Increasing river discharge to the Arctic Ocean
Bruce J. Peterson,Robert M. Holmes,James W. McClelland,Charles J. Vörösmarty,Richard B. Lammers,Alexander I. Shiklomanov,Igor A. Shiklomanov,Stefan Rahmstorf +7 more
TL;DR: Synthesis of river-monitoring data reveals that the average annual discharge of fresh water from the six largest Eurasian rivers to the Arctic Ocean increased by 7% from 1936 to 1999, a large-scale change in freshwater flux.
Journal ArticleDOI
Forcing of the cold event of 8,200 years ago by catastrophic drainage of Laurentide lakes
Donald C. Barber,Arthur S. Dyke,Claude Hillaire-Marcel,Anne E. Jennings,John T. Andrews,M. W. Kerwin,G Bilodeau,Roger McNeely,John R. Southon,Mark D. Morehead,Jean-Marc Gagnon +10 more
TL;DR: In this article, the authors argue that this cooling event was forced by a massive outflow of fresh water from the Hudson Strait, based on the estimates of the marine 14C reservoir for Hudson Bay which, in combination with other regional data, indicate that the glacial lakes Agassiz and Ojibway (originally dammed by a remnant of the Laurentide ice sheet) drained catastrophically ∼8,470 calendar years ago; this would have released >1014 m3 of freshwater into the Labrador Sea.
Journal ArticleDOI
Rapid changes of glacial climate simulated in a coupled climate model.
TL;DR: It is found that only one mode of Atlantic Ocean circulation is stable: a cold mode with deep water formation in the Atlantic Ocean south of Iceland; this provides an explanation why glacial climate is much more variable than Holocene climate.
Journal ArticleDOI
Ocean circulation and climate during the past 120,000 years
TL;DR: Evidence implicates ocean circulation in abrupt and dramatic climate shifts, such as sudden temperature changes in Greenland on the order of 5–10 °C and massive surges of icebergs into the North Atlantic Ocean.
References
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Journal ArticleDOI
The influence of the Bering Strait on the circulation in a coarse resolution global ocean model
C J C Reason,Scott B. Power +1 more
Abstract: An ocean general circulation model of global domain, full continental geometry and bottom topography, is used to study the influence of the Bering Strait on the general circulation by comparing equilibrium solutions obtained with and without a land-bridge between Siberia and Alaska. The model is integrated with restoring boundary conditions (BC) on temperature and salinity, and later, with mixed BC in which a restoring BC on temperature is maintained but a specified flux condition on salinity is imposed. In both cases, the effect of the Bering Strait is to allow a flow of about 1.25–1.5 Sv from the North Pacific to the Arctic Ocean and, ultimately, back to the North Pacific along the western boundary current regions of the Atlantic and Indian Oceans. When a restoring BC on salinity is used, the overturning associated with North Atlantic Deep Water and Antarctic Intermediate Water formation are increased if the Bering Strait is present in the model geometry. The result of switching to a specified flux BC on salinity is to cause a transition in the THC in which the overturning associated with North Atlantic Deep Water formation increases from about 12 Sv to about 22 Sv. This transition occurs in an essentially smooth fashion with no significant variability and is about 12% smaller in magnitude if the Bering Strait is present in the model geometry. Because the Bering Strait appears to exert some influence on the general circulation and the formation of deep water masses, it is recommended that this Strait be included in the geometry of similar resolution models designed to study the deep ocean and potential changes in climate.
Journal ArticleDOI
The mean circulation of the Atlantic Ocean north of 30s determined with the adjoint method applied to an ocean general circulation model
TL;DR: In this article, the large-scale mean circulation of the Atlantic Ocean is examined using a general circulation model and its approximate adjoint, where a cost function is specified that requires the model inputs to be consistent with hydrographic observations and observed air-sea fluxes of heat and freshwater, whereas the velocity field has to adjust to modified thermohaline initial and boundary conditions.
Book ChapterDOI
Mass and Heat Transports in the South Atlantic Derived from Historical Hydrographie Data
TL;DR: In this article, mass and heat transports in the South Atlantic as well as exchange flows with the South Pacific and the Indian Ocean are determined by driving a conservative, steady box-model towards the historical temperature (θ) and salinity (s) observations.
Journal ArticleDOI
On Oceanic Heat and Freshwater Fluxes at 30°S
TL;DR: In this paper, a simple box model based on mass, heat and salinity conservation combined with existing estimates of ocean-atmosphere heat and freshwater exchanges is used to calculate the oceanic mean meridional volume fluxes of three water masses at 30°S.
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