Wind forced oceanic responses near ice edges revisited

Fennel, Wolfgang; Johannessen, Ola M.

doi:10.1016/s0924-7963(97)00018-3

Cited by 16 publications

(22 citation statements)

References 17 publications

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“…Therefore, this mechanism cannot explain the bottom-intensified undercurrent. Similarly, Núñez-Riboni and Fahrbach [2009] suggest that the undercurrent they observed on the continental slope could be driven by the intensification of wind momentum transfer to the ocean by sea-ice [Fennel and Johannessen, 1998]. Again, the resulting currents should be surface-intensified, contrary to the observed undercurrents.…”

Section: Discussionmentioning

confidence: 95%

Observations of the Antarctic Slope Undercurrent in the southeastern Weddell Sea

Chavanne

Heywood

Nicholls

et al. 2010

Geophysical Research Letters

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The Antarctic Slope Front presents a dynamical barrier between the cold Antarctic shelf waters in contact with ice shelves and the warmer subsurface waters offshore. Two hydrographic sections with full‐depth current measurements were undertaken in January and February 2009 across the slope and shelf in the southeastern Weddell Sea. Southwestward surface‐intensified currents of ∼30 cm s−1, and northeastward undercurrents of 6–9 cm s−1, were in thermal‐wind balance with the sloping isopycnals across the front, which migrated offshore by 30 km in the time interval between the two sections. A mid‐depth undercurrent on February 23 was associated with a 130‐m uplift of the main pycnocline, bringing Warm Deep Water closer to the shelf break. This vertical displacement, comparable to that caused by seasonal variations in wind speed, implies that undercurrents may affect the exchanges between coastal and deep waters near the Antarctic continental margins.

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Section: Discussionmentioning

confidence: 95%

Observations of the Antarctic Slope Undercurrent in the southeastern Weddell Sea

Chavanne

Heywood

Nicholls

et al. 2010

Geophysical Research Letters

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“…Under these conditions, wind forcing has been shown to lead to along‐ice‐edge jets with upwelling and downwelling at the seaward and iceward side of the ice edge, respectively. This type of upwelling occurs on scales of a few kilometers, dependent on the wind velocity, ice drift, and the baroclinic Rossby Radius in the upper water column [ Fennel and Johannessen , ]. The deepened mixed layer at this station (Figure ) may have resulted from an earlier downwelling event and subsequent advection of surface waters and sea ice.…”

Section: Discussionmentioning

confidence: 99%

The influence of sea ice cover on air-sea gas exchange estimated with radon-222 profiles

Loeff

Cassar

Nicolaus

et al. 2014

J. Geophys. Res. Oceans

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Air-sea gas exchange plays a key role in the cycling of greenhouse and other biogeochemically important gases. Although air-sea gas transfer is expected to change as a consequence of the rapid decline in summer Arctic sea ice cover, little is known about the effect of sea ice cover on gas exchange fluxes, especially in the marginal ice zone. During the Polarstern expedition ARK-XXVI/3 (TransArc, August/September 2011) to the central Arctic Ocean, we compared 222 Rn/ 226 Ra ratios in the upper 50 m of 14 ice-covered and 4 ice-free stations. At three of the ice-free stations, we find 222 Rn-based gas transfer coefficients in good agreement with expectation based on published relationships between gas transfer and wind speed over open water when accounting for wind history from wind reanalysis data. We hypothesize that the low gas transfer rate at the fourth station results from reduced fetch due to the proximity of the ice edge, or lateral exchange across the front at the ice edge by restratification. No significant radon deficit could be observed at the ice-covered stations. At these stations, the average gas transfer velocity was less than 0.1 m/d (97.5% confidence), compared to 0.5-2.2 m/d expected for open water. Our results show that air-sea gas exchange in an ice-covered ocean is reduced by at least an order of magnitude compared to open water. In contrast to previous studies, we show that in partially ice-covered regions, gas exchange is lower than expected based on a linear scaling to percent ice cover.

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“…The simplified ALW vorticity equation retains enough complexity to illustrate the relation between the under‐ice sea level response, upwelling favorable winds and under‐ice friction while still allowing for the insight provided by an analytical solution. While ice edge processes have been considered before, previous studies [e.g., Gammelsrod et al , 1975; Clarke , 1978; Fennel and Johannessen , 1998] concentrated on wind‐forced motions near the ice edge rather than the circulation beneath the ice. In addition, they assumed a constant bottom depth, that the ice edge was far from any coastal boundaries, and they ignored along‐ and cross‐shore variations in ice properties, including under‐ice friction.…”

Section: Introductionmentioning

confidence: 99%

Modeling winter circulation under landfast ice: The interaction of winds with landfast ice

Kasper

Weingartner

2012

J. Geophys. Res.

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[1] Idealized models and a simple vertically averaged vorticity equation illustrate the effects of an upwelling favorable wind and a spatially variable landfast ice cover on the circulation beneath landfast ice. For the case of no along-shore variations in ice, upwelling favorable winds seaward of the ice edge result in vortex squashing beneath the landfast ice leading to (1) large decreases in coastal and ice edge sea levels, (2) cross-shore sea level slopes and weak (<$.05 m s À1) under-ice currents flowing upwind, (3) strong downwind ice edge jets, and (4) offshore transport in the under-ice and bottom boundary layers of the landfast ice zone. The upwind under-ice current accelerates quickly within 2-4 days and then slows as cross-shore transport gradually decreases the cross-shore sea level slope. Near the ice edge, bottom boundary layer convergence produces ice edge upwelling. Cross-ice edge exchanges occur in the surface and above the bottom boundary layer and reduce the under-ice shelf volume by 15% in 10 days. Under-ice along-shore pressure gradients established by along-and cross-shore variations in ice width and/or under-ice friction alter this basic circulation pattern. For a landfast ice zone of finite width and length, upwelling-favorable winds blowing seaward of and transverse to the ice boundaries induce downwind flow beneath the ice and generate vorticity waves that propagate along-shore in the Kelvin wave direction. Our results imply that landfast ice dynamics, not included explicitly herein, can effectively convert the long-wavelength forcing of the wind into shorter-scale ocean motions beneath the landfast ice.

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Wind forced oceanic responses near ice edges revisited

Cited by 16 publications

References 17 publications

Observations of the Antarctic Slope Undercurrent in the southeastern Weddell Sea

Observations of the Antarctic Slope Undercurrent in the southeastern Weddell Sea

The influence of sea ice cover on air-sea gas exchange estimated with radon-222 profiles

Modeling winter circulation under landfast ice: The interaction of winds with landfast ice

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