Modulation of Wind Work by Oceanic Current Interaction with the Atmosphere

AbstractIn this study, uncoupled and coupled ocean–atmosphere simulations are carried out for the California Upwelling System to assess the dynamic ocean–atmosphere interactions, namely, the ocean surface current feedback to the atmosphere. The authors show the current feedback, by modulating the energy transfer from the atmosphere to the ocean, controls the oceanic eddy kinetic energy (EKE). For the first time, it is demonstrated that the current feedback has an effect on the surface stress and a counteracting effect on the wind itself. The current feedback acts as an oceanic eddy killer, reducing by half the surface EKE, and by 27% the depth-integrated EKE. On one hand, it reduces the coastal generation of eddies by weakening the surface stress and hence the nearshore supply of positive wind work (i.e., the work done by the wind on the ocean). On the other hand, by inducing a surface stress curl opposite to the current vorticity, it deflects energy from the geostrophic current into the atmosphere and dampens eddies. The wind response counteracts the surface stress response. It partly reenergizes the ocean in the coastal region and decreases the offshore return of energy to the atmosphere. Eddy statistics confirm the current feedback dampens the eddies and reduces their lifetime, improving the realism of the simulation. Finally, the authors propose an additional energy element in the Lorenz diagram of energy conversion: namely, the current-induced transfer of energy from the ocean to the atmosphere at the eddy scale.

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Modulation of the Agulhas Current Retroflection and Leakage by Oceanic Current Interaction with the Atmosphere in Coupled Simulations

Journal of Physical Oceanography ◽

10.1175/jpo-d-16-0168.1 ◽

2017 ◽

Vol 47 (8) ◽

pp. 2077-2100 ◽

Cited By ~ 26

Author(s):

Lionel Renault ◽

James C. McWilliams ◽

Pierrick Penven

Keyword(s):

Energy Transfer ◽

Marine Boundary Layer ◽

Current System ◽

Surface Current ◽

Current Feedback ◽

Agulhas Current ◽

Benguela Upwelling ◽

Oceanic Eddy ◽

Ocean Surface Current ◽

Mean Circulation

AbstractCoupled ocean–atmosphere simulations are carried out for the Mozambique Channel, the Agulhas Current system, and the Benguela upwelling system to assess the ocean surface current feedback to the atmosphere and its impact on the Agulhas Current (AC) retroflection and leakage. Consistent with previous studies, the authors show that the current feedback slows down the oceanic mean circulation and acts as an oceanic eddy killer by modulating the energy transfer between the atmosphere and the ocean, reducing by 25% the mesoscale energy and inducing a pathway of energy transfer from the ocean to the atmosphere. The current feedback, by dampening the eddy kinetic energy (EKE), shifts westward the distribution of the AC retroflection location, reducing the presence of eastern retroflections in the simulations and improving the realism of the AC simulation. By modulating the EKE, the AC retroflection and the Good Hope jet intensity, the current feedback allows a larger AC leakage (by 21%), altering the water masses of the Benguela system. Additionally, the eddy shedding is shifted northward and the Agulhas rings propagate less far north in the Atlantic. The current–wind coupling coefficient sw is not spatially constant: a deeper marine boundary layer induces a weaker sw. Finally the results indicate that the submesoscale currents may also be weakened by the current feedback.

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Control and Stabilization of the Gulf Stream by Oceanic Current Interaction with the Atmosphere

Journal of Physical Oceanography ◽

10.1175/jpo-d-16-0115.1 ◽

2016 ◽

Vol 46 (11) ◽

pp. 3439-3453 ◽

Cited By ~ 34

Author(s):

Lionel Renault ◽

M. Jeroen Molemaker ◽

Jonathan Gula ◽

Sebastien Masson ◽

James C. McWilliams

Keyword(s):

Gulf Stream ◽

Surface Stress ◽

Numerical Models ◽

Geostrophic Wind ◽

Current Feedback ◽

Ocean Surface Currents ◽

Oceanic Eddy ◽

Current Interaction ◽

The Mean ◽

The Tropics

AbstractThe Gulf Stream (GS) is known to have a strong influence on climate, for example, by transporting heat from the tropics to higher latitudes. Although the GS transport intensity presents a clear interannual variability, satellite observations reveal its mean path is stable. Numerical models can simulate some characteristics of the mean GS path, but persistent biases keep the GS separation and postseparation unstable and therefore unrealistic. This study investigates how the integration of ocean surface currents into the ocean–atmosphere coupling interface of numerical models impacts the GS. The authors show for the first time that the current feedback, through its eddy killing effect, stabilizes the GS separation and postseparation, resolving long-lasting biases in modeled GS path, at least for the Regional Oceanic Modeling System (ROMS). This key process should therefore be taken into account in oceanic numerical models. Using a set of oceanic and atmospheric coupled and uncoupled simulations, this study shows that the current feedback, by modulating the energy transfer from the atmosphere to the ocean, has two main effects on the ocean. On one hand, by reducing the mean surface stress and thus weakening the mean geostrophic wind work by 30%, the current feedback slows down the whole North Atlantic oceanic gyre, making the GS narrower and its transport weaker. Yet, on the other hand, the current feedback acts as an oceanic eddy killer, reducing the surface eddy kinetic energy by 27%. By inducing a surface stress curl opposite to the current vorticity, it deflects energy from the geostrophic current into the atmosphere and dampens eddies.

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Oceanic eddy signature on SAR-derived sea ice drift and vorticity

10.5194/egusphere-egu21-2233 ◽

2021 ◽

Author(s):

Angelina Cassianides ◽

Camillie Lique ◽

Anton Korosov

Keyword(s):

Sea Ice ◽

Surface Current ◽

Satellite Observation ◽

The Arctic ◽

Global Ocean ◽

Sar Images ◽

Surface Ocean ◽

Ice Drift ◽

Sea Ice Drift ◽

Oceanic Eddy

In the global ocean, mesoscale eddies are routinely observed from satellite observation. In the Arctic Ocean, however, their observation is impeded by the presence of sea ice, although there is a growing recognition that eddy may be important for the evolution of the sea ice cover. In this talk, we will present a new method of surface ocean eddy detection based on their signature in sea ice vorticity retrieved from Synthetic Aperture Radar (SAR) images. A combination of Feature Tracking and Pattern Matching algorithm is used to compute the sea ice drift from pairs of SAR images. We will mostly focus on the case of one eddy in October 2017 in the marginal ice zone of the Canadian Basin, which was sampled by mooring observations, allowing a detailed description of its characteristics. Although the eddy could not be identified by visual inspection of the SAR images, its signature is revealed as a dipole anomaly in sea ice vorticity, which suggests that the eddy is a dipole composed of a cyclone and an anticyclone, with a horizontal scale of 80-100 km and persisted over a week. We will also discuss the relative contributions of the wind and the surface current to the sea ice vorticity. We anticipate that the robustness of our method will allow us to detect more eddies as more SAR observations become available in the future.

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Enhancement of doppler centroid for ocean surface current retrieval from ERS-1/2 raw SAR

IEEE International IEEE International IEEE International Geoscience and Remote Sensing Symposium, 2004. IGARSS '04. Proceedings. 2004 ◽

10.1109/igarss.2004.1370359 ◽

2004 ◽

Author(s):

Ji-Eun Kim ◽

Duk-jin Kim ◽

Wooil M. Moon

Keyword(s):

Surface Current ◽

Ocean Surface ◽

Ocean Surface Current

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Wave-Dependent Directional Biases in Airborne Ocean Surface Current Estimation

IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium ◽

10.1109/igarss.2018.8518985 ◽

2018 ◽

Cited By ~ 1

Author(s):

Shadi Aslebagh ◽

Gordon Farquharson ◽

John D. Sahr ◽

Rol Romeiser

Keyword(s):

Surface Current ◽

Ocean Surface ◽

Current Estimation ◽

Ocean Surface Current

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Ocean surface current prediction based on HF radar observations using trajectory-oriented association rule mining

2017 IEEE International Conference on Big Data (Big Data) ◽

10.1109/bigdata.2017.8258457 ◽

2017 ◽

Author(s):

Kulsawasd Jitkajornwanich ◽

Peerapon Vateekul ◽

Upa Gupta ◽

Teeranai Kormongkolkul ◽

Arnon Jirakittayakorn ◽

...

Keyword(s):

Association Rule ◽

Association Rule Mining ◽

Surface Current ◽

Ocean Surface ◽

Hf Radar ◽

Rule Mining ◽

Radar Observations ◽

Ocean Surface Current

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Influence of coastal upwelling on the surface current in the Bay of Bengal using HF radar and satellite observations

10.5194/egusphere-egu21-15747 ◽

2021 ◽

Author(s):

Shouvik Dey ◽

Sourav Sil ◽

Samiran Mandal

Keyword(s):

Coastal Upwelling ◽

Surface Current ◽

Hf Radar ◽

Second Phase ◽

Biological Productivity ◽

Maximum Peak ◽

Current Observation ◽

Ekman Layers ◽

Ocean Surface Current ◽

Upwelling Index

Coastal Upwelling is a phenomenon in which cold and nutrient-enriched water from the Ekman layers reaches the surface enhancing the biological productivity of the upwelling region. In this work, an attempt is made to understand the influence of coastal upwelling on surface current variations during May 2018 to August 2018, when HF radar current observation (source: NIOT, India) is available. The wind-based Upwelling Index(UIwind) showed coastal upwelling throughout the study period. But the SST based upwelling index (UIsst) showed upwelling occurred only from May to the first week of June. Cross-shore components of HF radar-derived ocean surface current (CSSC)&#160; showed strong similarity with UIsst. The first phase of upwelling from UIsst is observed to start on 5th May and lasts till 14th May with a maximum peak on around 10th May and having a horizontal extension of ~40 km. Then, there is a break period for about three days and after that, the second phase of upwelling starts on 17th May and lasts till 25th May with a maximum peak on around 20th May, but this time the horizontal extension is ~100 km which is much larger than during the first phase. A strong positive (from coast to offshore) CSSC is observed to start on around 5th May and lasts till 13th May with a maximum peak on around 10th May and having a horizontal extension of ~40 km, as observed from UIsst. A reversal of CSSC (towards coast) is noted on 14th May when the break of coastal upwelling is evident from UIsst. The CSSC then again started intensifying 15th May onwards and continued for ten days till 25th May, similar to UIsst.&#160; The horizontal extension of the upwelling signature in the second phase of upwelling is ~70 km. Therefore, a 7-10 days of the coastal upwelling and its horizontal extension are identified in this study. This study suggests the use of high resolution (~6 km) HF radar current observation on the monitoring of coastal upwelling processes.

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