Stability of North Atlantic Deep Water Formation in a Global Ocean General Circulation Model

Power, Scott B.; Smith, Neville; Kleeman, Richard; Moore, A. M.; Post, D. A.

doi:10.1175/1520-0485(1994)024<0904:sonadw>2.0.co;2

Cited by 17 publications

(4 citation statements)

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“…The important factors in the ocean response are the amplitude, duration, and timing of the sea ice pulse: about 1000 km 3 of sea ice exits through the Denmark Strait within 6 months during fall and early winter. If this amount would have been distributed evenly throughout 1 yr, a very weak response would have resulted: less than 0.5 Sv change in overturning cell as discussed by Power et al (1994). The study is not pre-senting the GSA as a part of an interdecadal cycle, but as a process involving sea ice that can influence decadal to interdecadal variability in the subtropical and subpolar North Atlantic.…”

Section: Discussionmentioning

confidence: 92%

“…Although the observational evidence supports that the GSA was a major climatic event, a modeling study by Power et al (1994) suggests that a freshwater excess of one or two GSA, distributed evenly over 5 yr (north of the sills, into the Greenland Sea), causes hardly any changes in the overturning cell. Their results suggest that it takes seven to eight times the GSA freshwater anomaly to be added to the system before a collapse of the thermohaline cell occurs.…”

Section: Introductionmentioning

confidence: 97%

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A Simulation of Thermohaline Effects of a Great Salinity Anomaly

Häkkinen¹

1999

J. Climate

131

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Model simulations of an idealistic ''Great Salinity Anomaly'' (GSA) demonstrate that variability in the sea ice export from the Arctic when concentrated to short pulses can have a large influence on the meridional heat transport and can lead to an altered overturning state. One single freshwater disturbance resulting from excess ice export, as in 1968, can disrupt the deep mixing process. The critical condition for a large oceanic response is defined by the intensity, duration, and timing of the ice pulse, in particular, as it exits through the Denmark Strait. A recovery from this event takes several years for advection and diffusion to remove the salinity anomaly. Concurrently, the influence of the GSA propagates to the subtropics via the boundary currents and baroclinic adjustment. As a result of this adjustment, there are large (up to 20%) changes in the strength of the overturning cell and in the meridional heat transport in the subtropics and subpolar areas. Simulations show a temperaturesalinity shift toward colder and fresher subpolar deep waters after the GSA, which is also found in hydrographic data.

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Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 97%

A Simulation of Thermohaline Effects of a Great Salinity Anomaly

Häkkinen¹

1999

J. Climate

131

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“…For a mixed layer 50 m deep these correspond to values of of 97 W m Ϫ2 K Ϫ1 and 81 W m Ϫ2 K Ϫ1 , respectively. As pointed out by a number or authors (Zhang et al 1993;Power et al 1994;Santer et al 1995;Rahmstorf and Willibrand 1995;Pierce et al 1995;Cai and Chu 1996), change of values of has detrimental effects on the realism of a modeled thermohaline circulation. Thus, use of a proper value becomes an important issue.…”

Section: Timescale Dependence Of For the Gradient-type Conditionsmentioning

confidence: 99%

On Haney-Type Surface Thermal Boundary Conditions for Ocean Circulation Models

1998

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Haney-type surface thermal boundary conditions linearly connect net downward surface heat flux Q to air-sea temperature difference (gradient-type condition) T 1 or to climate/synoptic sea temperature difference (re-storing-type condition) T 2 by a coupling coefficient. In this study, the authors used the global reanalyzed data (6-h resolution) of Q, surface air temperature T A , and sea surface temperature T O from the National Centers for Environmental Prediction during 1 October 1994-31 December 1995 to verify the validity of Haney-type surface thermal boundary conditions. First, daily means of these variables were computed to get rid of diurnal variation. Second, the cross-correlation coefficients (CCC) between Q and (T 1 , T 2) were calculated. The ensemble mean CCC fields show (i) no correlation between Q and T 2 anywhere in the world oceans, (ii) no correlation between Q and T 1 in the equatorial regions, and (c) evident correlation (CCC 0.7) between Q and T 1 in the middle and high latitudes. Third, the variance analysis was conducted and a value of 70 W m 2 K 1 (65 W m 2 K 1) was suggested for the coupling coefficient in the northern (southern) middle and high latitude zone. Thus, the authors find that the restoring-type surface thermal conditions by no means represent the net air-ocean heat flux anywhere in the world oceans. However, the gradient-type surface thermal condition represents the net heat flux quite well for the middle and high latitudes. In addition, it is also found that, if the solar shortwave component is treated separately, the gradient-type condition will have more fidelity for the middle and high latitudes.

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“…Paleoclimate data [e.g., Keigwin et al, 1991] and climate models [e.g., Manabe and Stouffer, 1988;Power et al, 1994] suggest that it is the thermohaline circulation which maintains the import of warm surface waters to the high latitudes. The idea is that during glacial climates, the thermohaline overturning is greatly reduced.…”

Section: Relationship Of the Ocean Circulation To Climatementioning

confidence: 99%

Tracers, time scales, and the thermohaline circulation: The lower limb in the North Atlantic Ocean

Fine¹

1995

Reviews of Geophysics

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This paper reviews the contributions of transient tracer research to our understanding of the lower limb of the thermohaline circulation in the North Atlantic Ocean. The review is limited geographically to the North Atlantic because of its importance for decadal scale climate variability. The tracers reviewed are the transient tracers of anthropogenic origin that give decadal time scale information, the chlorofluorocarbons (CFCs) and tritium/3He. The emphasis is on work by United States (US) investigators from 1991–94. Also included are some non‐US and earlier contributions as they are linked to the recent work and have not been reviewed in this publication before.

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Stability of North Atlantic Deep Water Formation in a Global Ocean General Circulation Model

Cited by 17 publications

References 0 publications

A Simulation of Thermohaline Effects of a Great Salinity Anomaly

A Simulation of Thermohaline Effects of a Great Salinity Anomaly

On Haney-Type Surface Thermal Boundary Conditions for Ocean Circulation Models

Tracers, time scales, and the thermohaline circulation: The lower limb in the North Atlantic Ocean

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