A Climatology of Wintertime Barrier Winds off Southeast Greenland

Harden, Benjamin E.; Renfrew, Ian A.; Petersen, Guðrún Nína

doi:10.1175/2011jcli4113.1

Cited by 93 publications

(136 citation statements)

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“…Especially the pressure is in excellent agreement with the observations [Harden et al, 2011]. During high wind speed conditions the 10m-winds are underrepresented by ∼1 m s −1 and the 2m-air temperature has a cold bias of ∼2°C.…”

Section: Datasupporting

confidence: 86%

“…Greenland itself likely plays a crucial role in forcing the cross-coastal flows, as previous studies have found that the interaction of the large-scale atmosphere with the high topography (shown in Figure 1-1a) creates strong wind events, particularly near the east coast [Moore, 2003]. These include tip jets around the southern tip of Greenland [Doyle and Shapiro, 1999, Våge et al, 2009, Moore and Renfrew, 2005, Renfrew et al, 2009a, Outten et al, 2009 and barrier winds at different locations along the east coast [Moore and Renfrew, 2005, Harden et al, 2011, Harden and Renfrew, 2012, Moore, 2012, and it was found that both types of wind events are associated with deep cyclones. In fact, the regions off the southwest, southeast and east Greenland coast are characterized by a particularly high cyclone frequency and large deepening rates [Zhang et al, 2004, Tsukernik et al, 2007.…”

Section: Introductionmentioning

confidence: 84%

“…The first could be attributed to a stronger pressure gradient build-up when the flow is dammed against the barrier, similar to barrier winds at the coast [Moore and Renfrew, 2005, Harden et al, 2011, but here the barrier is represented by the southwestern side of the valley and rotation is likely less important due to the smaller scale. There is a sharp turning of the isobars inside the valley (Figure 4-1).…”

Section: Mountain Wave -Gravity Current Interactionmentioning

confidence: 94%

“…During high wind speed conditions the 10m-winds are underrepresented by ∼1 m s −1 and the 2m-air temperature has a cold bias of ∼2°C. Dropsonde measurements have been compared to the vertical structure of the ERA-I output [Harden et al, 2011, Renfrew et al, 2008 and it was found that even though the basic structure of the wind and the temperature field is captured, ERA-I tends to underestimate the strength of gradients during high wind speed conditions. Over the Greenland ice sheet, the 10m-wind field was compared to observations from automated weather stations [Moore et al, 2013] and it was found that the data agree with root mean square errors of ∼1 m s −1 and correlations of ∼0.65.…”

Section: Datamentioning

confidence: 99%

“…The interaction of synoptic weather systems with the high topography can result in intense wind events, particularly around southern Greenland, which is one of the windiest regions in the World Ocean [Sampe and Xie, 2007]. Among these wind events are tip jets around the southern tip of Greenland [Doyle and Shapiro, 1999, Våge et al, 2009, Moore and Renfrew, 2005, Renfrew et al, 2009a, Outten et al, 2009, barrier winds at different locations along the east coast [Moore and Renfrew, 2005, Harden et al, 2011, Harden and Renfrew, 2012, Moore, 2012 and plateau jets along the eastern and western margin of the ice sheet [Moore et al, 2013]. Observations indicate the existence of another type of wind event associated with a strong downslope flow across Greenland's southeast coast Heinemann, 2002, Mills andAnderson, 2003], but to date there has been no comprehensive study about this type of wind event, and winds across Greenland's coast, either onshore or offshore, have generally received very limited attention.…”

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confidence: 99%

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Strong wind events across Greenland�s coast and their influence on the ice sheet, sea ice and ocean

Oltmanns¹

2015

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In winter, Greenland's coastline adjacent to the subpolar North Atlantic and Nordic Seas is characterized by a large land-sea temperature contrast. Therefore, winds across the coast advect air across a horizontal temperature gradient and can result in significant surface heat fluxes both over the ice sheet (during onshore winds) and over the ocean (during offshore winds). Despite their importance, these winds have not been investigated in detail, and this thesis includes the first comprehensive study of their characteristics, dynamics and impacts. Using an atmospheric reanalysis, observations from local weather stations, and remote sensing data, it is suggested that high-speed wind events across the coast are triggered by the superposition of an upper level potential vorticity anomaly on a stationary topographic Rossby wave over Greenland, and that they intensify through baroclinic instability. Onshore winds across Greenland's coast can result in increased melting, and offshore winds drive large heat losses over major ocean convection sites.Strong offshore winds across the southeast coast are unique over Greenland, because the flow is funneled from the vast ice sheet inland into the narrow valley of Ammassalik at the coast, where it can reach hurricane intensity. In this region, the cold air, which formed over the northern ice sheet, is suddenly released during intense downslope wind events and spills over the Irminger Sea where the cold and strong winds can drive heat fluxes of up to 1000 W m −2 , with potential implications for deep water formation. Moreover, the winds advect sea ice away from the coast and out of a major glacial fjord.Simulations of these wind events in Ammassalik with the atmospheric Weather Research and Forecast Model show that mountain wave dynamics contribute to the acceleration of the downslope flow. In order to capture these dynamics, a high model 3 resolution with a detailed topography is needed. The effects of using a different resolution locally in the valley extend far downstream over the Irminger Sea, which has implications for the evolution and distribution of the heat fluxes.

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Section: Datasupporting

confidence: 86%

Section: Introductionmentioning

confidence: 84%

Section: Mountain Wave -Gravity Current Interactionmentioning

confidence: 94%

Section: Datamentioning

confidence: 99%

mentioning

confidence: 99%

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Strong wind events across Greenland�s coast and their influence on the ice sheet, sea ice and ocean

Oltmanns¹

2015

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The oceanic response to mesoscale atmospheric forcing

Jung

Serrar

Wang

2014

Geophysical Research Letters

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The response of the oceanic circulation to mesoscale atmospheric forcing is studied by comparing integrations of a global sea ice-ocean model with high-resolution European Centre for Medium-Range Weather Forecasts analysis data (0.4 • ) to those with the same forcing coarse grained to a resolution typically employed in climate models and atmospheric reanalyses (1.8 • ). It is shown that the representation of mesoscale features in atmospheric forcing fields leads to an increase in the strength of the wind-driven gyres in the North Atlantic and North Pacific regions of about 5-10% of its mean value. An increase of similar magnitude is found for the Atlantic meridional overturning circulation. From the results of this study it is argued that small-scale atmospheric phenomena such as fronts, mesoscale cyclones, and topographic jets play an important role in driving the mean oceanic circulation.

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Characteristics and dynamics of two major Greenland glacial fjords

2014

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The circulation regimes of two major outlet glacial fjords in southeastern Greenland, Sermilik Fjord (SF) and Kangerdlugssuaq Fjord (KF), are investigated using data collected in summer 2009. The two fjords show similar flow patterns, with a time-dependent, vertically sheared flow structure dominating over the background estuarine flow driven by buoyancy input. We show that this time-dependent flow is consistent with circulation induced by density interface fluctuations at the fjord mouth, often referred to as intermediary circulation. One difference between the fjords is that the hydrographic and velocity structure below a surface modified layer is found to be three layer in KF in summer, compared to two layer in SF. Outside each fjord, large-scale geostrophic currents dictate the stratification at the mouth, although the way in which these large-scale flows impinge on each fjord is distinct. Combining the observations with estimates from existing theories, we find the magnitudes of the estuarine (Q e ) and intermediary (Q i ) circulation and show that Q i >> Q e , although along-fjord winds can also be significant. We expect that the critical parameter determining Q i /Q e is the sill depth compared to the fjord depth, with shallower sills corresponding to weaker intermediary circulation. Finally, we discuss the implications of strong intermediary circulation on calculating heat transport to the glacier face and its potential feedbacks on the background circulation in these highly stratified estuaries.

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A Climatology of Wintertime Barrier Winds off Southeast Greenland

Cited by 93 publications

References 50 publications

Strong wind events across Greenland�s coast and their influence on the ice sheet, sea ice and ocean

Strong wind events across Greenland�s coast and their influence on the ice sheet, sea ice and ocean

The oceanic response to mesoscale atmospheric forcing

Characteristics and dynamics of two major Greenland glacial fjords

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