Supplementary material to "Seasonal and regional variations of sinking in the subpolar North Atlantic from a high-resolution ocean model"

Abstract The authors present the first quantitative comparison between new velocity datasets and high-resolution models in the North Atlantic subpolar gyre [1/10° Parallel Ocean Program model (POPNA10), Miami Isopycnic Coordinate Ocean Model (MICOM), ⅙° Atlantic model (ATL6), and Family of Linked Atlantic Ocean Model Experiments (FLAME)]. At the surface, the model velocities agree generally well with World Ocean Circulation Experiment (WOCE) drifter data. Two noticeable exceptions are the weakness of the East Greenland coastal current in models and the presence in the surface layers of a strong southwestward East Reykjanes Ridge Current. At depths, the most prominent feature of the circulation is the boundary current following the continental slope. In this narrow flow, it is found that gridded float datasets cannot be used for a quantitative comparison with models. The models have very different patterns of deep convection, and it is suggested that this could be related to the differences in their barotropic transport at Cape Farewell. Models show a large drift in watermass properties with a salinization of the Labrador Sea Water. The authors believe that the main cause is related to horizontal transports of salt because models with different forcing and vertical mixing share the same salinization problem. A remarkable feature of the model solutions is the large westward transport over Reykjanes Ridge [10 Sv (Sv ≡ 106 m3 s−1) or more].

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Dissecting the Barotropic Transport in a High-resolution ocean model

10.5194/egusphere-egu2020-18490 ◽

2020 ◽

Author(s):

Martin Claus ◽

Yuan Wang ◽

Richard Greatbatch ◽

Jinyu Sheng

Keyword(s):

High Resolution ◽

North Atlantic ◽

Spatial Scales ◽

Ocean Model ◽

Water Model ◽

North Atlantic Current ◽

The North ◽

Circulation Patterns ◽

Resolution Model ◽

High Resolution Model

We present a method to decompose the time mean vertically averaged transport, as simulated by an high-resolution ocean model, into its four dominant components. These components are driven by the gradient of potential energy per unit area (PE), the divergence of the flux of time mean momentum (MMF) and eddy momentum (EMF), and the wind stress. Since the local vorticity budget and the bathymetry are noisy and dominated by small spatial scales, a barotropic shallow water model is used as a filter to diagnose the respective transports instead of integrating along lines of constant f/H. Applying this method to the output of a high-resolution model of the North Atlantic we find that PE is the most important driver, including the northwest corner. MMF is an important driver of transport around the Labrador Sea continental slope and, together with the EMF, it drives significant transport along the path of the Gulf Stream and North Atlantic current. Additionally, the circulation patterns driven by the EMF compares well with an estimate based on a satellite product. Hence, the presented method provides insights into the relative importance of the different dynamical processes that may drive barotropic transport in an ocean model. But it may also be used to isolate potential issues if a model misrepresents the barotropic transport.

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Decomposing barotropic transport variability in a high-resolution ocean model of the North Atlantic Ocean

10.5194/egusphere-egu2020-8399 ◽

2020 ◽

Author(s):

Yuan Wang ◽

Richard Greatbatch ◽

Martin Claus ◽

Jinyu Sheng

Keyword(s):

High Resolution ◽

North Atlantic ◽

Gulf Stream ◽

North Atlantic Ocean ◽

Momentum Equation ◽

Ocean Model ◽

Recirculation Region ◽

Mean Flow ◽

The North ◽

Stream Transport

Temporal variability of the annual mean barotropic streamfunction in a high-resolution model configuration (VIKING20) for the northern North Atlantic is analyzed using a decomposition technique based on the vertically-averaged momentum equation. The method is illustrated by examining how the Gulf Stream transport in the recirculation region responds to the winter North Atlantic Oscillation (NAO). While no significant response is found in the year overlapping with the winter NAO index, a tendency is found for the Gulf Stream transport to increase as the NAO becomes more positive, starting in lead years 1 and 2 when the mean flow advection (MFA) and eddy momentum flux (EMF) terms associated with the nonlinear terms dominate in the momentum equations. Only after 2 years, the potential energy (PE) term, associated with the density field, starts to play a role and it is only after 5 years that the transport dependence on the NAO ceases to be significant. The PE contribution to the transport streamfunction has significant memory of up to 5 years in the Labrador and Irminger Seas. However, it is only around the northern rim of these seas that VIKING20 and the transport reconstruction exhibit similar memory. This is due to masking by the nonlinear MFA and EMF contributions.

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Seasonal and regional variations of sinking in the subpolar North Atlantic from a high-resolution ocean model

Ocean Science ◽

10.5194/os-15-1033-2019 ◽

2019 ◽

Vol 15 (4) ◽

pp. 1033-1053 ◽

Cited By ~ 2

Author(s):

Juan-Manuel Sayol ◽

Henk Dijkstra ◽

Caroline Katsman

Keyword(s):

High Resolution ◽

North Atlantic ◽

Seasonal Variability ◽

Ocean Model ◽

Meridional Overturning Circulation ◽

Boundary Current ◽

Meridional Transport ◽

Marginal Seas ◽

Complex Picture ◽

Mean Fields

Abstract. Previous studies have indicated that most of the net sinking associated with the downward branch of the Atlantic Meridional Overturning Circulation (AMOC) must occur near the subpolar North Atlantic boundaries. In this work we have used monthly mean fields of a high-resolution ocean model (0.1∘ at the Equator) to quantify this sinking. To this end we have calculated the Eulerian net vertical transport (W∑) from the modeled vertical velocities, its seasonal variability, and its spatial distribution under repeated climatological atmospheric forcing conditions. Based on this simulation, we find that for the whole subpolar North Atlantic W∑ peaks at about −14 Sv at a depth of 1139 m, matching both the mean depth and the magnitude of the meridional transport of the AMOC at 45∘ N. It displays a seasonal variability of around 10 Sv. Three sinking regimes are identified according to the characteristics of the accumulated W∑ with respect to the distance to the shelf: one within the first 90 km and onto the bathymetric slope at around the peak of the boundary current speed (regime I), the second between 90 and 250 km covering the remainder of the shelf where mesoscale eddies exchange properties (momentum, heat, mass) between the interior and the boundary (regime II), and the third at larger distances from the shelf where W∑ is mostly driven by the ocean's interior eddies (regime III). Regimes I and II accumulate ∼90 % of the total sinking and display smaller seasonal changes and spatial variability than regime III. We find that such a distinction in regimes is also useful to describe the characteristics of W∑ in marginal seas located far from the overflow areas, although the regime boundaries can shift a few tens of kilometers inshore or offshore depending on the bathymetric slope and shelf width of each marginal sea. The largest contributions to the sinking come from the Labrador Sea, the Newfoundland region, and the overflow regions. The magnitude, seasonal variability, and depth at which W∑ peaks vary for each region, thus revealing a complex picture of sinking in the subpolar North Atlantic.

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High-Resolution Ocean Model Captures Large-Scale Heat Transport

Eos ◽

10.1029/2016eo062103 ◽

2016 ◽

Cited By ~ 1

Author(s):

Sarah Stanley

Keyword(s):

High Resolution ◽

Heat Transport ◽

North Atlantic ◽

Large Scale ◽

Ocean Model ◽

Sea Surface ◽

The North ◽

Resolution Model ◽

High Resolution Model ◽

The North Atlantic

A lower-resolution model is sufficient to capture air-sea interactions, but a high-resolution model better simulates average sea surface temperatures in the North Atlantic.

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Seasonal and regional variations of sinking in the subpolar North Atlantic from a high-resolution ocean model

10.5194/os-2019-27 ◽

2019 ◽

Author(s):

Juan-Manuel Sayol ◽

Henk Dijkstra ◽

Caroline Katsman

Keyword(s):

High Resolution ◽

North Atlantic ◽

Seasonal Variability ◽

Ocean Model ◽

Meridional Overturning Circulation ◽

Boundary Current ◽

Meridional Transport ◽

Marginal Seas ◽

Complex Picture ◽

Mean Fields

Abstract. Previous studies have indicated that most of the net sinking associated with the downward branch of the Atlantic Meridional Overturning Circulation (AMOC) must occur near the subpolar North Atlantic boundaries. In this work we have used monthly mean fields of a high-resolution ocean model (0.1 deg at the equator) to quantify this sinking. To this end we have calculated the Eulerian net vertical transport (WΣ) from the modelled vertical velocities, its seasonal variability and its spatial distribution under repeated climatological atmospheric forcing conditions. Based on this simulation, we find that for the whole subpolar North Atlantic WΣ peaks at about −14 Sv at a depth of 1139 m, matching both the mean depth and the magnitude of the meridional transport of the AMOC at 45° N. It displays a seasonal variability of around 10 Sv. Three sinking regimes are identified according to the characteristics of the accumulated W with respect to the distance to the coast: one within the first 110 km and onto the bathymetric slope at around the peak of the boundary current speed (regime I), the second between 110 km and 290 km covering the remainder of the shelf where mesoscale eddies exchange properties (momentum, heat, mass) between the interior and the boundary (regime II), and the third sinking regime at larger distances from the coast where WΣ is mostly driven by the ocean's interior eddies (regime III). Regimes I and II accumulate ∼ 90 % of the total sinking and display smaller seasonal changes and spatial variability than regime III. We find that such a distinction in regimes is also useful to describe the characteristics of WΣ in marginal seas located far from the overflow areas, although the regime boundaries can shift a few tens of km inshore or offshore depending on the bathymetric slope and shelf width of each marginal sea. The largest contributions to the sinking come from the Labrador Sea, the Newfoundland region and the overflow regions. The magnitude, the seasonal variability and the depth at which WΣ peaks vary for each region, thus revealing a complex picture of sinking in the subpolar North Atlantic.

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Supplementary material to "Role of wind, mesoscale dynamics and coastal circulation in the interannual variability of South Vietnam Upwelling, South China Sea. Answers from a high resolution ocean model"

10.5194/os-2021-121-supplement ◽

2022 ◽

Author(s):

Thai To Duy ◽

Marine Herrmann ◽

Claude Estournel ◽

Patrick Marsaleix ◽

Thomas Duhaut ◽

...

Keyword(s):

High Resolution ◽

South China Sea ◽

Interannual Variability ◽

South China ◽

Ocean Model ◽

Coastal Circulation ◽

Mesoscale Dynamics ◽

South Vietnam ◽

Supplementary Material

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An analysis of extra-tropical storms in the North Atlantic region as simulated in a control and 2 × CO2time-slice experiment with a high-resolution atmospheric model

Tellus A Dynamic Meteorology and Oceanography ◽

10.3402/tellusa.v49i3.14674 ◽

1997 ◽

Vol 49 (3) ◽

pp. 347-361 ◽

Cited By ~ 14

Author(s):

J.J. Beersma ◽

K.M. Rider ◽

G.J. Komen ◽

E. Kaas ◽

V.V. Kharin

Keyword(s):

High Resolution ◽

North Atlantic ◽

Atmospheric Model ◽

Tropical Storms ◽

North Atlantic Region ◽

Atlantic Region ◽

The North ◽

The North Atlantic

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Matchup Characteristics of Sea Surface Salinity Using a High-Resolution Ocean Model

Remote Sensing ◽

10.3390/rs13152995 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2995

Author(s):

Frederick M. Bingham ◽

Severine Fournier ◽

Susannah Brodnitz ◽

Karly Ulfsax ◽

Hong Zhang

Keyword(s):

High Resolution ◽

Time Window ◽

Single Point ◽

Ocean Model ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Argo Floats ◽

Statistical Measures ◽

Salinity Difference

Sea surface salinity (SSS) satellite measurements are validated using in situ observations usually made by surfacing Argo floats. Validation statistics are computed using matched values of SSS from satellites and floats. This study explores how the matchup process is done using a high-resolution numerical ocean model, the MITgcm. One year of model output is sampled as if the Aquarius and Soil Moisture Active Passive (SMAP) satellites flew over it and Argo floats popped up into it. Statistical measures of mismatch between satellite and float are computed, RMS difference (RMSD) and bias. The bias is small, less than 0.002 in absolute value, but negative with float values being greater than satellites. RMSD is computed using an “all salinity difference” method that averages level 2 satellite observations within a given time and space window for comparison with Argo floats. RMSD values range from 0.08 to 0.18 depending on the space–time window and the satellite. This range gives an estimate of the representation error inherent in comparing single point Argo floats to area-average satellite values. The study has implications for future SSS satellite missions and the need to specify how errors are computed to gauge the total accuracy of retrieved SSS values.

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