Early Spring Oceanic Heat Fluxes and Mixing Observed from Drift Stations North of Svalbard*

Sirevaag, Anders; Fer, Ilker

doi:10.1175/2009jpo4172.1

Cited by 51 publications

(59 citation statements)

References 39 publications

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“…In the pycnocline above the Atlantic Water layer, Padman and Dillon (1991) observed an upward heat flux of 25 W m −2 , which decreased to 6 W m −2 below the surface mixed layer. These mixing rates and heat fluxes are strong and comparable to those observed over the shelves north of Svalbard and in proximity to the West Spitsbergen Current branches (Fer and Sundfjord, 2007;Sirevaag and Fer, 2009). Here, we hypothesize that spatially varying tides and their baroclinic response over topography are responsible for the observed variability and mixing near the YP.…”

Section: Introductionsupporting

confidence: 69%

Tidal forcing, energetics, and mixing near the Yermak Plateau

2015

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Abstract. The Yermak Plateau (YP), located northwest of Svalbard in Fram Strait, is the final passage for the inflow of warm Atlantic Water into the Arctic Ocean. The region is characterized by the largest barotropic tidal velocities in the Arctic Ocean. Internal response to the tidal flow over this topographic feature locally contributes to mixing that removes heat from the Atlantic Water. Here, we investigate the tidal forcing, barotropic-to-baroclinic energy conversion rates, and dissipation rates in the region using observations of oceanic currents, hydrography, and microstructure collected on the southern flanks of the plateau in summer 2007, together with results from a global high-resolution ocean circulation and tide model simulation. The energetics (depthintegrated conversion rates, baroclinic energy fluxes and dissipation rates) show large spatial variability over the plateau and are dominated by the luni-solar diurnal (K 1 ) and the principal lunar semidiurnal (M 2 ) constituents. The volumeintegrated conversion rate over the region enclosing the topographic feature is approximately 1 GW and accounts for about 50 % of the M 2 and approximately all of the K 1 conversion in a larger domain covering the entire Fram Strait extended to the North Pole. Despite the substantial energy conversion, internal tides are trapped along the topography, implying large local dissipation rates. An approximate local conversion-dissipation balance is found over shallows and also in the deep part of the sloping flanks. The baroclinic energy radiated away from the upper slope is dissipated over the deeper isobaths. From the microstructure observations, we inferred lower and upper bounds on the total dissipation rate of about 0.5 and 1.1 GW, respectively, where about 0.4-0.6 GW can be attributed to the contribution of hot spots of energetic turbulence. The domain-integrated dissipation from the model is close to the upper bound of the observed dissipation, and implies that almost the entire dissipation in the region can be attributed to the dissipation of baroclinic tidal energy.

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Section: Introductionsupporting

confidence: 69%

Tidal forcing, energetics, and mixing near the Yermak Plateau

2015

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“…The peak in total heat transport in 2004 seems to lead that of the temperature maximum occurring in 2006 (Schauer and Beszczynska-Mo¨ller, 2009). For ocean mixing in the Arctic, only snapshots in temporal and spatial coverage are available (Rainville and Winsor, 2008;Sirevaag and Fer, 2009). Any long-term changes, as well as a reasonable climatic annual mean for the region north of Svalbard, are not available.…”

Section: Discussionmentioning

confidence: 99%

Loss of sea ice during winter north of Svalbard

Onarheim

Smedsrud

Ingvaldsen

et al. 2014

Tellus A: Dynamic Meteorology and Oceanography

222

240

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A B S T R A C T Sea ice loss in the Arctic Ocean has up to now been strongest during summer. In contrast, the sea ice concentration north of Svalbard has experienced a larger decline during winter since 1979. The trend in winter ice area loss is close to 10% per decade, and concurrent with a 0.38C per decade warming of the Atlantic Water entering the Arctic Ocean in this region. Simultaneously, there has been a 28C per decade warming of winter mean surface air temperature north of Svalbard, which is 20Á45% higher than observations on the west coast. Generally, the ice edge north of Svalbard has retreated towards the northeast, along the Atlantic Water pathway. By making reasonable assumptions about the Atlantic Water volume and associated heat transport, we show that the extra oceanic heat brought into the region is likely to have caused the sea ice loss. The reduced sea ice cover leads to more oceanic heat transferred to the atmosphere, suggesting that part of the atmospheric warming is driven by larger open water area. In contrast to significant trends in sea ice concentration, Atlantic Water temperature and air temperature, there is no significant temporal trend in the local winds. Thus, winds have not caused the long-term warming or sea ice loss. However, the dominant winds transport sea ice from the Arctic Ocean into the region north of Svalbard, and the local wind has influence on the year-to-year variability of the ice concentration, which correlates with surface air temperatures, ocean temperatures, as well as the local wind.

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“…Microstructure measurements conducted during the IPY show that the Arctic Ocean is a quiescent environment with background mixing rates close to molecular levels (Rainville and Winsor, 2008;Fer, 2009). Efficient vertical mixing and upward oceanic heat fluxes occur, however, along the continental rise and over topographic features where the warm boundary current is guided (Sirevaag and Fer, 2009;Fer et al, 2010). An illustration of the main forcing mechanisms and physical processes leading to diapycnal mixing are summarized in Fig.…”

Section: Diapycnal Mixing In the Arctic Oceanmentioning

confidence: 99%

Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

et al. 2014

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Abstract. The Arctic climate system includes numerous highly interactive small-scale physical processes in the atmosphere, sea ice, and ocean. During and since the International Polar Year 2007-2009, significant advances have been made in understanding these processes. Here, these recent advances are reviewed, synthesized, and discussed. In atmospheric physics, the primary advances have been in cloud physics, radiative transfer, mesoscale cyclones, coastal, and fjordic processes as well as in boundary layer processes and surface fluxes. In sea ice and its snow cover, advances have been made in understanding of the surface albedo and its relationships with snow properties, the internal structure of sea ice, the heat and salt transfer in ice, the formation of superimposed ice and snow ice, and the small-scale dynamics of sea ice. For the ocean, significant advances have been related to exchange processes at the ice-ocean interface, diapycnal mixing, double-diffusive convection, tidal currents and diurnal resonance. Despite this recent progress, some of these small-scale physical processes are still not sufficiently understood: these include wave-turbulence interactions in the atmosphere and ocean, the exchange of heat and salt at the ice-ocean interface, and the mechanical weakening of sea ice. Many other processes are reasonably well understood as stand-alone processes but the challenge is to understand their interactions with and impacts and feedbacks on other processes. Uncertainty in the parameterization of small-scale processes continues to be among the greatest challenges facing climate modelling, particularly in high latitudes. Further improvements in parameterization require new year-round field campaigns on the Arctic sea ice, closely combined with satellite remote sensing studies and numerical model experiments.

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Early Spring Oceanic Heat Fluxes and Mixing Observed from Drift Stations North of Svalbard*

Cited by 51 publications

References 39 publications

Tidal forcing, energetics, and mixing near the Yermak Plateau

Tidal forcing, energetics, and mixing near the Yermak Plateau

Loss of sea ice during winter north of Svalbard

Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

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