Microstructure Observations of Turbulent Heat Fluxes in a Warm-Core Canada Basin Eddy

Fine, Elizabeth C.; MacKinnon, Jennifer A.; Alford, Matthew H.; Mickett, John B.

doi:10.1175/jpo-d-18-0028.1

Cited by 40 publications

(102 citation statements)

References 97 publications

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“…Here, we present the analysis of observations collected during the first glider mission in an anticyclonic LCE (“Poseidon”; Meunier et al, 2018) in fall 2016. Double diffusion processes are common attributes of eddies in the ocean (Bebieva & Timmermans, 2016; Fine et al, 2018), and our findings indicate that LCEs are not an exception.…”

Section: Introductionsupporting

confidence: 64%

Turbulent Mixing in a Loop Current Eddy From Glider‐Based Microstructure Observations

Molodtsov

Anis

Amon

et al. 2020

Geophysical Research Letters

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Turbulence parameters have been estimated from microstructure velocity and temperature measurements in an anticyclonic Loop Current Eddy in the Gulf of Mexico for the very first time. Measurements were performed during a mission in October 2016, using a G2 Webb Research Slocum ocean glider instrumented with a microstructure sensors suite. Well‐defined turbulent kinetic energy dissipation rate patterns in the eddy and the surface mixed layer were clearly identified from both the velocity and temperature microstructure data. Higher dissipation rates were observed at the flanks and beneath the eddy core (up to 10−7 W/kg), while the core interior appeared to be very quiescent (~10−11 W/kg). Double diffusive thermohaline intrusions were detected on the side of the eddy, while the region below the eddy core was more conducive for salt fingering. Heat and salt fluxes associated with these processes suggest that a life span of such an eddy is ~1.5 years.

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Section: Introductionsupporting

confidence: 64%

Turbulent Mixing in a Loop Current Eddy From Glider‐Based Microstructure Observations

Molodtsov

Anis

Amon

et al. 2020

Geophysical Research Letters

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“…Mesoscale eddies are commonly observed in the Arctic Ocean via field campaigns (D'Asaro, ; Hunkins, ; Padman et al, ; Pickart, ), from drifting ice‐tethered profilers (Timmermans et al, ; Zhao et al, , ) and moorings (Zhao et al, ; Zhao & Timmermans, ), as well as in microstructure observations in Canada Basin (Fine et al, ). Depending on their geographic location and depth in the water column, there is a multitude of possible eddy formation mechanisms in the Arctic including baroclinic and barotropic instabilities of mean flows including boundary currents (D'Asaro, ; Johannessen et al, ; Manley & Hunkins, ; Spall et al, ); convection‐driven eddies in, for example, leads of polynyas (Muench et al, ); instabilities of outcropping surface fronts (Manucharyan & Timmermans, ); mixed layer instabilities of meltwater fronts (Lu, ; Manucharyan & Thompson, ); and wind‐driven eddy formation over ice‐edge boundaries (Johannessen et al, ).…”

Section: Introductionmentioning

confidence: 99%

Eddies in the Western Arctic Ocean From Spaceborne SAR Observations Over Open Ocean and Marginal Ice Zones

et al. 2019

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The Western Arctic Ocean is a host to major ocean circulation systems, many of which generate eddies that can transport water masses and corresponding tracers over long distances from their formation sites. However, comprehensive observations of critical eddy characteristics are currently not available and are limited to spatially and temporally sparse in situ observations. Here we use high-resolution spaceborne synthetic aperture radar measurements to detect eddies from their surface imprints in ice-free sea surface roughness, and in sea ice patterns throughout marginal ice zones. We provide the first estimate of eddy characteristics extending over the seasonally ice-free and marginal ice zone regions of the Western Arctic Ocean, including their locations, diameters, and monthly distribution. Using available synthetic aperture radar data, we identified over 4,000 open ocean eddies, as well as over 3,500 eddies in marginal ice zones from June to October in 2007, 2011, and 2016. Eddies range in size between 0.5 and 100 km and are frequently found over the shelf and near continental slopes but also present in the deep Canada Basin and over the Chukchi Plateau. We find that cyclonic eddies are twice more frequent compared to anticyclonic eddies at the surface, distinct from the dominating anticyclonic eddies observed at depth by in situ moorings and ice-tethered profilers. Our study supports the notion that eddies are ubiquitous in the Western Arctic Ocean even in the presence of sea ice and emphasizes the need for improved ocean observations and modeling at eddy scales. Plain Language SummaryOcean eddies play an important role in the transport of heat, salt, and pollutants over long distances from their formation sites. However, their observations in the Arctic Ocean are complex due to severe weather and sea ice cover. Here we present results of high-resolution satellite observations over the ice-free ocean and in the marginal ice zones. Detailed eddy characteristics are for the first time presented for the Western Arctic Ocean. These results provide observational evidence that eddies are ubiquitous in this Arctic region even in the presence of sea ice and emphasize the need for improved ocean observations and modeling at eddy scales. Key Points: • First account of eddies in the Western Arctic Ocean is presented based on satellite observations over open ocean and marginal ice zones • Eddies range in size between 0.5 and 100 km and are ubiquitous over deep and shelf regions of the Western Arctic Ocean • Cyclonic eddies are twice more frequent compared to anticyclones

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“…Using an inverse method and repeat hydrographic measurements between 2003 and 2015, Dosser and Timmermans () estimated along‐isopycnal diffusivity in the Canada Basin to be 300–600 m 2 s −1 . Using high‐resolution measurements from an intrahalocline eddy on the Chukchi slope, Fine et al () quantified contribution of different processes to the heat loss of the eddy. At the top edge of the eddy, double diffusion led to an upward heat flux of 5 W m −2 , at the bottom edge shear‐driven mixing generated a downward heat flux of 0.5 W m −2 , and along the sides density‐compensated thermohaline intrusions transported 2,000 W m −2 laterally out of the eddy.…”

Section: Introductionmentioning

confidence: 99%

Observations of Turbulence at a Near‐Surface Temperature Front in the Arctic Ocean

et al. 2020

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High-resolution ocean temperature, salinity, current, and turbulence data were collected at an Arctic thermohaline front in the Nansen Basin. The front was close to the sea ice edge and separated the cold and fresh surface melt water from the warm and saline mixed layer. Measurements were made on 18 September 2018, in the upper 100 m, from a research vessel and an autonomous underwater vehicle. Destabilizing surface buoyancy fluxes from a combination of heat loss to the atmosphere and cross-front Ekman transport by down-front winds reduced the potential vorticity in the upper ocean. Turbulence structure in the mixed layer was generally consistent with turbulence production through convection by heat loss to atmosphere and mechanical forcing by moderate winds. Conditions at the front were favorable for forced symmetric instability, a mechanism drawing energy from the frontal geostrophic current. A clear signature of increased dissipation from symmetric instability could not be identified; however, this instability could potentially account for the increased dissipation rates at the front location down to 40 m depth that could not be explained by the atmospheric forcing. This turbulence was associated with turbulent heat fluxes of up to 10 W m −2 , eroding the warm and cold intrusions observed between 30 and 60 m depth. A Seaglider sampled across a similar frontal structure in the same region 10 days after our survey. The submesoscale-to-turbulence-scale transitions and resulting mixing can be widespread and important in the Atlantic sector of the Arctic Ocean. Plain Language SummaryOn 18 September 2018, high-resolution temperature, salinity, current, and turbulence data were collected near a surface temperature and salinity front in the Nansen Basin north of Svalbard, within the framework of the Nansen Legacy Project. Measurements were performed from the research icebreaker Kronprins Haakon and using an autonomous underwater vehicle. The front separates warm and salty Atlantic-origin waters from cold and fresh Arctic-origin waters. Energetic turbulence in the upper 30 m was consistent with convection by heat loss to the atmosphere and mechanical forcing by moderate winds at the surface of the ocean. At the front, the conditions were favorable for forced symmetric instability, a mechanism drawing energy from the large-scale current. The contribution to turbulence from this instability could not be clearly identified but can be potentially important. Such observations linking 1-3 km scales to turbulence in the Arctic Ocean are rare. Turbulence at a front in the Arctic has consequences on the heat and nutrient transport from the slope to the deep Arctic Basin. A Seaglider sampled across a similar frontal structure in the same region end of September 2018. Observed frontal structure and mixing processes can be common in the Atlantic sector of the Arctic Ocean.

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Microstructure Observations of Turbulent Heat Fluxes in a Warm-Core Canada Basin Eddy

Cited by 40 publications

References 97 publications

Turbulent Mixing in a Loop Current Eddy From Glider‐Based Microstructure Observations

Turbulent Mixing in a Loop Current Eddy From Glider‐Based Microstructure Observations

Eddies in the Western Arctic Ocean From Spaceborne SAR Observations Over Open Ocean and Marginal Ice Zones

Observations of Turbulence at a Near‐Surface Temperature Front in the Arctic Ocean

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