Mesoscale Subduction at the Antarctic Polar Front Driven by Baroclinic Instability

Garabato, Alberto C. Naveira; Leach, Harry; Allen, John T.; Pollard, Raymond T; Strass, Volker

doi:10.1175/1520-0485(2001)031<2087:msatap>2.0.co;2

Cited by 49 publications

(24 citation statements)

References 63 publications

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“…Another way to estimate the vertical velocity is to solve the ω equation (Rudnick, ). However, the resulting patterns are highly sensitive to the precise numerical initial conditions (e.g., Garabato et al, ) and the survey took too long to synoptically resolve the velocity and density in 3‐D. (Ship‐powered towed profiling systems can complete a similar survey in ≈8 hr that might be sufficiently synoptic.)…”

Section: Resultsmentioning

confidence: 99%

Observations of a Submesoscale Cyclonic Filament in the Marginal Ice Zone

Appen

Wekerle

Hehemann

et al. 2018

Geophysical Research Letters

104

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Submesoscale flows are energetic motions on scales of several kilometers that may lead to substantial vertical motions. Here we present satellite and ship radar as well as underway conductivity-temperature-depth and Acoustic Doppler Current Profiler observations of a cyclonic submesoscale filament in the marginal ice zone of Fram Strait. The filament created a 500-m thin and 50-km long sea ice streak and extends to >250-m depth with a negative/positive density anomaly within/below the halocline. The frontal jets of 0.5 m/s are in turbulent thermal wind balance while the ageostrophic secondary circulation in places appears to subduct Atlantic Water at >50 m/day. Our study reveals the submesoscale dynamics related to sea ice shapes that can be sensed remotely and shows how submesoscale dynamics contribute to shaping the marginal ice zone. It also demonstrates the co-occurrence and mixing of water masses over short horizontal scales, which has implications for ocean and sea ice models and understanding of patch formation of planktonic organisms.Plain Language Summary A sea ice streak in the marginal ice zone was observed with radar measurements. Below this streak in situ shipboard measurements of the temperature, salinity, and velocity field revealed a cyclonic submesoscale filament. This is a line of denser water of a few kilometers width bounded by strong counteracting velocities. This denser water is also associated with a different water mass and thus a change in biological properties and communities. This provides in situ confirmation for previous theoretical conclusions of how oceanic flows on kilometer scales structure the sea ice and biology in the marginal ice zone. The understanding of such small-scale processes helps improve computer models of the ocean and sea ice dynamics. It also makes it possible to interpret oceanic flows from remote sensing of sea ice. Furthermore, it gives indication over which horizontal scales biological processes vary in the ocean.

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Section: Resultsmentioning

confidence: 99%

Observations of a Submesoscale Cyclonic Filament in the Marginal Ice Zone

Appen

Wekerle

Hehemann

et al. 2018

Geophysical Research Letters

104

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“…[32] The input of nutrients along fronts, for example in the Southern Ocean due to meanders of the Polar Front [Naveiro Garabato et al, 2001], or in the equatorial Pacific by upwelling at the trailing edge of TIWs [Friedrichs and Hoffmann, 2001] may also contribute to the increase in diatom biomass. However, conventional blooms, such as those characterized in the equatorial Pacific, equatorial Atlantic and Southern Ocean by Pseudo-nitschia and other lightly silicified species are rarely found in the sediment due to dissolution effects [Lange et al, 1994;Abrantes and Moita, 1999;C.…”

Section: Giant Diatoms and Fronts: A Summarymentioning

confidence: 99%

Production of giant marine diatoms and their export at oceanic frontal zones: Implications for Si and C flux from stratified oceans

Kemp

Pearce

Grigorov³

et al. 2006

Global Biogeochemical Cycles

110

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From a synthesis of recent oceanic observations and paleo‐data it is evident that certain species of giant diatoms including Rhizosolenia spp. Thalassiothrix spp. and Ethmodiscus rex may become concentrated at oceanic frontal zones and subsequently form episodes of mass flux to the sediment. Within the nutrient bearing waters advecting towards frontal boundaries, these species are generally not dominant, but they appear selectively segregated at fronts, and thus may dominate the export flux. Ancient Thalassiothrix diatom mat deposits in the eastern equatorial Pacific and beneath the Polar Front in the Southern Ocean record the highest open ocean sedimentation rates ever documented and represent vast sinks of silica and carbon. Several of the species involved are adapted to a stratified water column and may thrive in Deep Chlorophyll Maxima. Thus in oceanic regions and/or at times prone to enhanced surface water stratification (e.g., during meltwater pulses) they provide a mechanism for generating substantial biomass at depth and its subsequent export with concomitant implications for Si export and C drawdown. This ecology has important implications for ocean biogeochemical models suggesting that more than one diatom “functional type” should be used. In spite of the importance of these giant diatoms for biogeochemical cycling, their large size coupled with the constraints of conventional oceanographic survey schemes and techniques means that they are undersampled. An improved insight into these key species will be an important prerequisite for enhancing our understanding of marine biogeochemical cycling and for assessing the impacts of climate change on ocean export production.

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“…The SeaSoar towed, undulating vehicle (Allen et al 2002;Pollard 1986) is well proven for surveying mesoscale fronts and eddies (Allen and Smeed 1996;Allen et al 2005;Garabato et al 2001;Legal et al 2007;Martin et al 1998;Pollard and Regier 1992;Rudnick 1996). Undulating between the surface and ;500-m depth, carrying a variety of sensors, SeaSoar provides highfrequency (1 Hz) near-instantaneous mapping of upperocean properties: typically temperature, salinity, pressure, chlorophyll-a fluorescence, and photosynthetically active radiation (PAR).…”

Section: Introductionmentioning

confidence: 99%

A Novel Integration of an Ultraviolet Nitrate Sensor On Board a Towed Vehicle for Mapping Open-Ocean Submesoscale Nitrate Variability

Pidcock

Srokosz

Allen

et al. 2010

Journal of Atmospheric and Oceanic Technology

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Initial results from a deployment of the SUV-6 ultraviolet spectrophotometer, integrated with the SeaSoar towed vehicle, are presented. The innovative, combined system measures nitrate concentration at high spatial resolution (4 m vertically, 5 km horizontally), high sensitivity (0.2 mM), and concomitantly with temperature, salinity, and dissolved oxygen. The authors demonstrate that this approach constitutes a powerful new tool for quantifying the role of mesoscale and submesoscale vertical nutrient fluxes to the euphotic zone, using measurements from a high-resolution survey of an eddy dipole in the Iceland Basin during the summer of 2007.

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Mesoscale Subduction at the Antarctic Polar Front Driven by Baroclinic Instability

Cited by 49 publications

References 63 publications

Observations of a Submesoscale Cyclonic Filament in the Marginal Ice Zone

Observations of a Submesoscale Cyclonic Filament in the Marginal Ice Zone

Production of giant marine diatoms and their export at oceanic frontal zones: Implications for Si and C flux from stratified oceans

A Novel Integration of an Ultraviolet Nitrate Sensor On Board a Towed Vehicle for Mapping Open-Ocean Submesoscale Nitrate Variability

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