Preconditioning the Greenland Sea for deep convection: Ice formation and ice drift

Visbeck, Martin; Fischer, Jürgen; Schott, Friedrich

doi:10.1029/95jc01611

Cited by 70 publications

(82 citation statements)

References 31 publications

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“…To reproduce the observed changes in the mixed layer they found that a net export of 0.005 m d\ of ice out of the area was required, about 1/3 of ice production estimated by Roach et al (1993). From model calculations Visbeck et al (1995) concluded that the entrainment from below became so strong that the ice started to melt before the mixed layer convected. After the ice cover was removed a deep thermal convection was established.…”

Section: The Greenland Seamentioning

confidence: 99%

“…Deep, thermal convection was established and continued for the rest of the winter. Visbeck (1993) and Visbeck et al (1995) studied the same area and period using observations from moored thermistor chains and ADCPs, and applied a one-dimensional mixed-layer model forced by real meteorological data. To reproduce the observed changes in the mixed layer they found that a net export of 0.005 m d\ of ice out of the area was required, about 1/3 of ice production estimated by Roach et al (1993).…”

Section: The Greenland Seamentioning

confidence: 99%

“…We therefore also discuss the e!ects of the convection events on the second layer. Based upon the results of the Greenland Sea Project (GSP group, 1990;Roach et al, 1993;Schott et al, 1993;Visbeck et al, 1995) it is assumed that the two upper layers together make up 600 m of the water column, and we follow the evolution of the second layer as well as the mixed layer. The mixed layer convects when it reaches marginal stability.…”

Section: The Greenland Seamentioning

confidence: 99%

“…The formulation of the buoyancy #ux used by Walin (1993) and Visbeck et al (1995) is di!erent from the one applied by Lemke (1987), Lemke et al (1990), Houssais (1988) and Houssais and Hibler (1993). Walin (1993) balances entrained heat with heat lost to the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

“…In the Weddell Sea, which was the focus of Walin's discussion, the duration of the freezemelting period has to be signi"cantly longer than the span of the winter to remove the ice, and the ice cover would normally remain and melt the following summer. Visbeck et al (1995) applied a similar model to the Greenland Sea. They derived a similar pattern of ice growth and melting and, assuming a partial export of the ice cover, a situation arose where the ice disappeared and the mixed layer deepened rapidly.…”

Section: Introductionmentioning

confidence: 99%

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On the parameterisation of oceanic sensible heat loss to the atmosphere and to ice in an ice-covered mixed layer in winter

Rudels¹,

Friedrich

Hainbucher

et al. 1999

Deep Sea Research Part II: Topical Studies in Oceanography

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In high-latitude oceans with seasonal ice cover, the ice and the low-salinity mixed layer form an interacting barrier for the heat #ux from the ocean to the atmosphere. The presence of a less dense surface layer allows ice to form, and the ice cover reduces the heat loss to the atmosphere. The ice formation weakens the stability at the base of the mixed layer, leading to stronger entrainment and larger heat #ux from below. This heat transport retards, and perhaps stops, the growth of the ice cover. As much heat is then entrained from below as is lost to the atmosphere. This heat loss further reduces the stability, and unless a net ice melt occurs, the mixed layer convects. Two possibilities exist: (1) A net ice melt, su$cient to retain the stability, will always occur and convection will not take place until all ice is removed. The deep convection will then be thermal, deepening the mixed layer. (2) The ice remains until the stability at the base of the mixed layer disappears. The mixed layer then convects, through haline convection, into the deep ocean. Warm water rises towards the surface and the ice starts to melt, and a new mixed layer is reformed. The present work discusses the interactions between ice cover and entrainment during winter, when heat loss to the atmosphere is present. One crucial hypothesis is introduced:`When ice is present and the ocean loses sensible heat to the atmosphere and to ice melt, the buoyancy input at the sea surface due to ice melt is at a minimuma. Using a onedimensional energy-balance model, applied to the arti"cial situation, where ice melts directly on warmer water, it is found that this corresponds to a constant fraction of the heat loss going to ice melt. It is postulated that this partitioning holds for the ice cover and the mixed layer in the high-latitude ocean. When a constant fraction of heat goes to ice melt, at least one deep 0967-0645/99/$ -see front matter 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 7 -0 6 4 5 ( 9 9 ) 0 0 0 2 8 -4 convection event occurs, before the ice cover can be removed by heat entrained from below. After one or several convection events the ice normally disappears and a deep-reaching thermal convection is established. Conditions appropriate for the Weddell Sea and the Greenland Sea are examined and compared with "eld observations. With realistic initial conditions no convection occurs in the warm regime of the Weddell Sea. A balance between entrained heat and atmospheric heat loss is established and the ice cover remains throughout the winter. At Maud Rise convection may occur, but late in winter and normally no polynya can form before the summer ice melt. In the central Greenland Sea the mixed layer generally convects early in winter and the ice is removed by melting from below as early as February or March. This is in agreement with existing observations.

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Section: The Greenland Seamentioning

confidence: 99%

Section: The Greenland Seamentioning

confidence: 99%

Section: The Greenland Seamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

On the parameterisation of oceanic sensible heat loss to the atmosphere and to ice in an ice-covered mixed layer in winter

Rudels¹,

Friedrich

Hainbucher

et al. 1999

Deep Sea Research Part II: Topical Studies in Oceanography

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Fram Strait and Greenland Sea transports, water masses, and water mass transformations 1999–2010 (and beyond)

et al. 2016

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The exchanges between the Nordic Seas and the Arctic Ocean are important for the ocean circulation and climate. Transports are here estimated using summer hydrographic data from the Greenland Sea and the Fram Strait. Geostrophic transports are computed from hydrographic sections at 75°N in the Greenland Sea and at about 79°N in the Fram Strait. Geostrophic velocities are adjusted with summer velocities derived from Argo floats, and four conservation constraints are applied to a box closed by the two sections. The estimated net volume transports are 0.8 ± 1.5 Sv southward. Net freshwater transports through the Greenland Sea section are estimated at 54 ± 20 mSv and through the Fram Strait section at 66 ± 9 mSv. Heat loss in the area between the two sections is estimated at 9 ± 12 TW. Convection depths in the Greenland Sea are estimated from observations and vary between about 200 and 2000 dbar showing no trend. Water mass properties in the Greenland Sea are affected both by convection and lateral mixing. Vertical mixing is estimated from hydrography and based on it about 1 Sv of diluted Arctic Ocean waters are estimated to enter the Greenland Sea. The properties of Atlantic, intermediate, and deep waters are studied. Deep water properties are defined using water mass triangles and are subject to decadal changes.

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Nordic Seas Heat Loss, Atlantic Inflow, and Arctic Sea Ice cover over the last century

Smedsrud

Brakstad

Madonna

et al. 2021

Preprint

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Poleward ocean heat transport is a key process in the earth system. We detail and review the northward Atlantic Water (AW) flow, Arctic Ocean heat transport, and heat loss to the atmosphere since 1900 in relation to sea ice cover. Our synthesis is largely based on a sea ice-ocean model forced by a reanalysis atmosphere corroborated by a comprehensive hydrographic database (1950-), AW inflow observations (1996-), and other long-term time series of sea ice extent (1900-), glacier retreat (1984-), and Barents Sea hydrography (1900-). The Arctic Ocean, including the Nordic and Barents Seas, has warmed since the 1970s. This warming is congruent with increased ocean heat transport and sea ice loss and has contributed to the retreat of marine-terminating glaciers on Greenland. Heat loss to the atmosphere is largest in the Nordic Seas (60% of total) with large variability linked to the frequency of Cold Air Outbreaks and cyclones in the region, but there is no long-term statistically significant trend. Heat loss from the Barents Sea (∼30%) and Arctic seas farther north (∼10%) is overall smaller, but exhibit large positive trends. The AW inflow, total heat loss to the atmosphere, and dense outflow have all increased since 1900. These are consistently related through theoretical scaling, but the AW inflow increase is also wind-driven. The Arctic Ocean CO 2 uptake has increased by ∼30% over the last century-consistent with Arctic sea ice loss allowing stronger air-sea interaction and is ∼8% of the global uptake. Plain Language SummaryThe major flow to and from the Arctic Ocean occurs across the Greenland-Scotland Ridge. The inflow is mostly warm Atlantic Water (AW) flowing northwards and cooling gradually. After completing different loops within the Arctic Ocean, portions of this water eventually flows south as cold freshened polar water at the surface and cold, dense overflow water at depth. We review and synthesize how the AW cooling evolved over the last century in relation to the Arctic sea ice cover. In the mean 60% of the heat loss occurred in the Nordic Seas, 30% in the Barents Sea, and only 10% in the Arctic seas further north. Arctic sea ice decrease the last century created more open water and permitted stronger ocean heat loss. The ocean volume and heat transport also increased, consistently with increased heat loss, and increased wind forcing. Ocean temperatures have generally increased in many areas during the last 50 years, and on Greenland this drove the retreat of marine-terminating glaciers. Variability in ocean heat loss to the atmosphere was primarily driven by Cold Air Outbreaks and cyclones in the Nordic and Barents Seas, and explain variability in Arctic Ocean CO 2 uptake, being ∼8% of the global uptake.

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Preconditioning the Greenland Sea for deep convection: Ice formation and ice drift

Cited by 70 publications

References 31 publications

On the parameterisation of oceanic sensible heat loss to the atmosphere and to ice in an ice-covered mixed layer in winter

On the parameterisation of oceanic sensible heat loss to the atmosphere and to ice in an ice-covered mixed layer in winter

Fram Strait and Greenland Sea transports, water masses, and water mass transformations 1999–2010 (and beyond)

Nordic Seas Heat Loss, Atlantic Inflow, and Arctic Sea Ice cover over the last century

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