Observed and simulated kinematic properties of Loop Current rings

Kirwan, A. D.; Lewis, James K.; Indest, A. W.; Reinersman, Phillip N.; Quintero, Irvin

doi:10.1029/jc093ic02p01189

Cited by 56 publications

(31 citation statements)

References 19 publications

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“…and concentrations ( Vukovich and Crissman. 1986;Kirwan et al, 1988] and the following composite (May 1979), but it is unclear if this simulated anticyclonic eddies in the Gulf represents a remnant of the eddy.…”

Section: Oct -Ov Dementioning

confidence: 99%

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Arctic carbon sinks: Present and future

Walsh¹

1989

Global Biogeochemical Cycles

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92-30570I 17With past ONR support from Grant N00014-87-J-1218, we had successfully coupled simple biological models of phytoplankton production (light and nutrient regulation of one size fraction) to time-dependent, 3-dimensional physical models of basin circulation at 25-30 km resolution in the Gulf of Mexico . While these coupled models mimicked seasonal cycles of phytoplankton abundance in basin waters, as estimated by changes in chlorophyll stocks, they failed to replicate fluctuations of biological populations within more complex slope and shelf regions.Accordingly, a more diverse biological model of particle decay within the aphotic zone (3 size classes of phytoplankton, macroaggregates, and zooplankton fecal pellets) was coupled to a static, 2-dimensional model of slope circulation at 0.5 km resolution in the Middle Atlantic Bight (Walsh et al., 1991). By specifying the influx of these particles, both at the shelf-break and from the overlying slope euphotic zone, with variable sinking velocities, the second set of coupled models reproduced seasonal time series of organic carbon caught by moored sediment traps on the slope and rise.A total of 8 publications were derived from this ONR grant: yr-1 , gases, C0 2 , N 2 0, CH4, and freons, to the tenfold that of other high Arctic shelves, atmosphere, is attributed to altered ice/ and may supply 50% of the carbon snow albedo at sea level, i.e., melting of respiration demands within the halocline sea ice.A 5% decline of sea ice extent of the deep Canadian and Eurasian basins in the Arctic and Antarctic from 1979 to via brine-mediated runoff. Continued 1987 may have resulted in increased light melting of ice in the Arctic could availability within previously ice-covered increase by an order of magnitude the polar regions.If such a short-term trend present CO 2 sink of 1-0.i x 109 t C yr'. were to continue, it might lead to a negative biogeochemical feedback, i.e., enhanced extraction of atmospheric CO 2 INTRODUCTION during marine photosynthesis.As a consequence of deep vertical mixing in the The global temperature of surface air Antarctic Ocean, however, primary producincreaseu by 0.4*-0.5*C from 1880 to 1980, tion during the austral summer may have while temperatures of Arctic regions actually declined in response to a reduc-(%64*-90N) instead rose by as much as tion in extent of meltwater regions, where 1.2*-1.5 0 C over this period [Hansen et stratified water columns allow carbon al., 1983]. After 1980, six of the fixation tenfold that of open water.In warmest years in the past century have contrast, within shallow adjacent seas of subsequently been observed , 1981, the Arctic Ocean, where shelf regions are 1983, reflecting tenfold larger than those of the possible early signs of a "greenhouse" warming of the Earth [Hansen and Lebedeff, Copyright 1989Copyright 1988. Initial one-dimensional [Hansen et by the American Geophysical Union. al., 19811 and then three-dimensional climate models of varying sophisticationPaper number 90GB00583. [Mitchell,...

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Section: Oct -Ov Dementioning

confidence: 99%

“…1984;Biggs et al, 1984, 19911, andonly one attempt to andPechmann et al, 1986;Kirwan et al, rings repeatedly shed by this current (Vukovich et al, 1979;19801. It took 30 days to complete the latter survey (FebruVukovich and Maul, 1985;Vukovich, 1986Vukovich, , 1988aElliott, ary 25 to March 27.…”

Section: Introductionmentioning

confidence: 99%

Arctic carbon sinks: Present and future

Walsh¹

1989

Global Biogeochemical Cycles

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“…5) show time-varying patterns of meanders and eddies. Material is translated and sheared by jets and wrapped around elliptic eddies (Okubo, 1970;Kirwan et al, 1988). The current field has many hyperbolic singularities where there is a split in the path along which C 1 -material is transported.…”

Section: Runoff-driven Circulationmentioning

confidence: 99%

Circulation and the nutrient budget in Myall Lakes

Sanderson

2008

Hydrobiologia

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A two-dimensional model is used to study transport of material within Myall Lakes and is coupled to the ocean using a one-dimensional model of Lower Myall River. Runoff from the catchment is calculated from water levels and compares favourably with rainfall assuming an average runoff yield of 28% and a runoff coefficient of 47% for events above the 90th percentile. Most of the runoff enters Bombah Broadwater which is also the only basin connected to the ocean. Intermittent runoff events rapidly displace water from Bombah Broadwater into Boolambayte Lake and from Boolambayte Lake into Myall Lake. Displaced water is mixed within basins by winddriven circulation within the time scale that levels fall as water drains from the lakes to the ocean. Only 7% of the nutrient load entering Bombah Broadwater becomes resident Myall Lake. About 40% of the nutrient load entering Boolambayte Lake becomes resident in Myall Lake. Median time scales for loss of conservative material entering each basin with the runoff are: 140 days for Bombah Broadwater, 118 days for Boolambayte Lake, and 535 days for Myall Lake. Salinity fluctuates greatly in Bombah Broadwater but is stable in Myall Lake. Material loss from Bombah Broadwater is characterized by many time scales associated with runoff from the catchment and low-frequency changes in ocean water level. Comparison of observed distributions of total nitrogen with simulations indicates that there are sources of total nitrogen in Boolambayte Lake and Myall Lake and sinks of total nitrogen in Bombah Broadwater. There appear to be sinks of total phosphorus throughout the Myall Lakes.

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“…The Loop Current is known to shed large anticyclonic (warm) eddies, having a mean diameter ranging from 300 to 400 km, at least once a year (Elliott, 1982;Vukovich and Crissman, 1986). After these eddies separate from the Loop Current, they migrate to the western Gulf following mainly a southwestward path with an average speed of 2-6 km day~' (Elliott, 1982;Vukovich and Crissman, 1986;Kirwan et al, 1988). As an eddy approaches the (Mexican) continental slope, its shape (originally near-circular) changes to elliptical because of the interaction between the eddy, the coastal circulation and the bottom topography (Kirwan et al, 1988).…”

Section: E Eddy Propagation and Bottom Topography Interactionmentioning

confidence: 99%

“…After these eddies separate from the Loop Current, they migrate to the western Gulf following mainly a southwestward path with an average speed of 2-6 km day~' (Elliott, 1982;Vukovich and Crissman, 1986;Kirwan et al, 1988). As an eddy approaches the (Mexican) continental slope, its shape (originally near-circular) changes to elliptical because of the interaction between the eddy, the coastal circulation and the bottom topography (Kirwan et al, 1988). Once on the continental shelf, anticyclonic eddies are observed to intensify cyclonic features, and then both as a pair migrate northward along the isobaths (Merrell and Morrison, 1981;Merrell and Vazquez, 1983;Brooks, 1984;Kirwan et al, 1988).…”

Section: E Eddy Propagation and Bottom Topography Interactionmentioning

confidence: 99%

A generalized reduced‐gravity ocean model

Arango

Reid

1991

Atmosphere-Ocean

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A major difficulty with two-layer ocean models, except in the linear approximation, is encountered in situations where the interface intersects the seabed. For the single mode, reduced-gravity version it is assumed that a passive deep lower layer exists everywhere, which in fact precludes any influence by bathymetry. These restrictions can be removed by employing a realistic continuous density stratification. Discussed here is a generalized, equivalent barotropic model in isopycnic coordinates that is based on the gravest vertical structure function E(σ) for current determined by the global, levelled-state density distribution. The eigenvalue problem employs a rigid-lid condition at the sea surface and requires E = 0 (a vanishing current) at the seabed for each local depth h. The gravest mode has monotonie E(σ) and an associated eigencelerity that is typical of a first baroclinic mode. Both the structure function and the celerity (hence the Rossby deformation radius) depend on the local depth h. The E(σ) based on realistic levelled-state density stratification closely resembles the dominant first empirical mode commonly found from observed current structure at mid-latitudes. The non-linear governing equations (admitting both gravity and Rossby waves) are developed using an energy-conserving, Galerkin projection of the primitive equations of motion onto the adopted vertical structure, taking into account the dependence on h. The resulting governing equations involve two important depth-dependent parameters: the celerity (C e ) and a Flierl-type advection parameter (µ.). The role of bottom topography in this generalized, reduced-gravity model is illustrated via an application to the Loop Current evolution and to the interaction of mesoscale circulation features with bathymetry in the western Gulf of Mexico. This illustration employs a non-linear, quasi-geostrophic voracity version of the model in boundary-fitted, orthogonal curvilinear coordinates, implemented numerically. RÉSUMÉ Sauf dans le cas d'une approximation linéaire, les modèles d'un océan à deux couches présentent une difficulté considérable dans les situations où l'interface intersecte le lit de la mer. La version mode unique à gravité réduite suppose l'omniprésence d'une couche profonde, passive et sous-jacente. Cela exclut d'avance toute influence bathymétrique. Les restrictions peuvent être levées par l'emploi d'une stratification de densité continue et réaliste. Le présent article examine un modèle barotropique équivalent, généralisé, en coordonnées isopyeniques, qui se base sur la fonction de la structure verticale la plus énergétique E(σ) pour un courant déterminé par la distribution globale d'un état de densité A Generalized Reduced-Gravity Ocean Model / 257 nivelée. Le problème de la valeur propre emploie la condition du couvercle rigide à la surface de la mer et exige que E = 0 (un courant qui s'atténue) au niveau du lit de la mer pour chaque profondeur locale h. Le mode le plus énergétique possède un E(σ) monotone et une eigencélérité associée ...

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Observed and simulated kinematic properties of Loop Current rings

Cited by 56 publications

References 19 publications

Arctic carbon sinks: Present and future

Arctic carbon sinks: Present and future

Circulation and the nutrient budget in Myall Lakes

A generalized reduced‐gravity ocean model

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