Southern Ocean Mixed‐Layer Seasonal and Interannual Variations From Combined Satellite and In Situ Data

Nardelli, Bruno Buongiorno; Guinehut, S.; Verbrugge, Nathalie; Cotroneo, Yuri; Zambianchi, Enrico; Iudicone, Daniele

doi:10.1002/2017jc013314

Cited by 51 publications

(48 citation statements)

References 44 publications

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“…It is worth noting that the differences between water mass net subduction estimates obtained from mEOF‐r and ARMOR3D data are dominated by the discrepancies between MLD and geostrophic terms, rather than by the diagnosed vertical dynamics. As such, future analyses of long time series will have to be based on the products providing the most accurate retrieval of the mixed layer depth (such as version 4 of ARMOR3D reprocessed data set, Buongiorno Nardelli et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…These differences are clearly due to the different reconstruction of both horizontal gradients and vertical stratification in the two products. The version 3 of ARMOR3D, in particular, presents significantly lower variance at the mesoscale with respect to products ingesting multivariate high‐resolution sea surface salinity fields (Buongiorno Nardelli et al, ), while also generally displaying a significantly deeper MLD (Buongiorno Nardelli et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…The second data set is the experimental product ACCUA described in Buongiorno Nardelli et al (), which we briefly illustrate and further validate hereafter. The data set covers only the Southern Ocean (10°S–65°S) and is obtained through the mEOF‐r technique (Buongiorno Nardelli & Santoleri, ).…”

Section: Datamentioning

confidence: 99%

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Three‐Dimensional Ageostrophic Motion and Water Mass Subduction in the Southern Ocean

2018

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Vertical velocities at the ocean mesoscale are several orders of magnitude smaller than corresponding horizontal flows, making their direct monitoring a still unsolved challenge. Vertical motion is generally retrieved indirectly by applying diagnostic equations to observation‐based fields. The most common approach relies on the solution of an adiabatic version of the Omega equation, neglecting the ageostrophic secondary circulation driven by frictional effects and turbulent mixing in the boundary layers. Here we apply a diabatic semigeostrophic diagnostic model to two different 3‐D reconstructions covering the Southern Ocean during the period 2010–2012. We incorporate the effect of vertical mixing through a modified K‐profile parameterization and using ERA‐interim data, and perform an indirect validation of the ageostrophic circulation with independent drifter observations. Even if horizontal gradients and associated vertical flow are likely underestimated at 1/4° × 1/4° resolution, the exercise provides an unprecedented relative quantification of the contribution of vertical mixing and adiabatic internal dynamics on the vertical exchanges along the Antarctic Circumpolar Current. Kinematic estimates of subduction rates show the destruction of poleward flowing waters lighter than 26.6 kg/m3 (14 ÷ 15 Sv) and two main positive bands associated with the Antarctic Intermediate Water (7 ÷ 11 Sv) and Sub‐Antarctic Mode Waters (4 ÷ 7 Sv) formation, while Circumpolar Deep Water upwelling attains around 3 ÷ 6 Sv. Diabatic and adiabatic terms force distinct spatial responses and vertical velocity magnitudes along the water column and the restratifying effect of adiabatic internal dynamics due to mesoscale eddies is shown to at least partly compensate the contribution of wind‐driven vertical exchanges to net subduction.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Three‐Dimensional Ageostrophic Motion and Water Mass Subduction in the Southern Ocean

2018

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“…For more details about the density‐based MLD data set, see Buongiorno Nardelli et al . (). Among the experiments (MLD‐CONST, the MLD‐TEMP and MLD‐DENS), the present authors only changed the spatially varying MLDs while maintaining the same physics and domain configurations expected in the OML, and it was assumed that the simulated changes in track and intensity were primarily observed due to the combined effect of the initial MLD and the defined initial profile of temperature and density.…”

Section: Data Model Configuration and Experimental Detailsmentioning

confidence: 99%

Impact of ocean mixed‐layer depth initialization on the simulation of tropical cyclones over the Bay of Bengal using the WRF‐ARW model

Viswanadhapalli

Kattamanchi

Vissa

et al. 2019

Meteorological Applications

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The sensitivity of the simulated tropical cyclone (TC) intensity and tracks to the different ocean mixed‐layer depth (MLD) initializations is studied using coupled weather research and forecasting (WRF) and ocean mixed‐layer (OML) models. Four sets of numerical experiments are conducted for two TCs formed during the pre‐ and post‐monsoon. In the control run (CONTROL), the WRF model is initialized without coupling. In the second experiment, the WRF‐OML model is initialized by prescribing the MLD as a constant depth of 50 m (MLD‐CONST). In the third experiment, the spatial varying MLD obtained from the formulation of depth of the isothermal layer (MLD‐TEMP) is used. For the fourth experiment (MLD‐DENS), the model is initialized with the density‐based MLD obtained from ARMOR‐3D data. The results indicate that the CONTROL exhibits an early intensification phase with a faster translation movement, leading to early landfall and the production of large track deviations. The coupled OML simulations captured the deepening phase close to the observed estimates, resulting in the reduction of errors in both the vector and along the tracks of the storm. The initialization of the different estimates of the MLD in the WRF‐OML shows that the TC intensity and translation speed are sensitive to the initial representation of the MLD for the post‐monsoon storm. The gradual improvements in the intensity and translation speed of the storm with the realistic representation of the OML are mainly due to the storm‐induced cooling, which in turn alters the simulated enthalpy fluxes supplied to the TC, leading to the better representation of secondary circulation and the rapid intensification of the storm.

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“…The complex dynamics of Southern Ocean (SO) affects surface, intermediate and deep ocean circulation and characteristics over several temporal and spatial scales, e.g., [1][2][3][4][5][6][7]. The intense thermo-dynamical interactions between atmosphere and ocean have the potential to influence global climate, e.g., [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Different Behaviours of the Ross and Weddell Seas Surface Heat Fluxes in the Period 1972–2015

Fusco

Cotroneo

Aulicino

2018

Climate

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Abstract:Operational analyses and re-analyses, provided by ECMWF for the period 1972-2015, were used to investigate the behaviour of the surface heat fluxes between ocean and atmosphere, estimated via empirical formulae, over the Ross and Weddell Seas. The presence and thickness of sea ice cover, which strongly affects ocean-atmosphere interactions, was estimated through Special Sensor Microwave Imager and Special Sensor Microwave Imager Sounder brightness temperatures. Because of the lack of ice information before 1992, daily averaged ice and snow thickness obtained from the 1992-2012 dataset has been used as a 'climatological year' for the 1972-2015 period. The heat loss in the Ross Sea reached its maximum in 2008 (−98 W·m −2 ) and its minimum (−58 W·m −2 ) in 1980, while in the Weddell Sea, it ranged between −65 W·m −2 (1999) and −99 W·m −2 (2015). Results showed that the surface heat fluxes behaviour in the two seas moved from opposite to synchronous during the study period. The wavelet analysis was applied to evaluate if this result might be linked to the signature of global climate variability expressed by El Niño Southern Oscillation (ENSO) and Southern Annular Mode (SAM). The synchronous behaviour of the surface heat fluxes in the Ross and Weddell seas, observed since 2001, coincides with a change in the energy peak associated to the time scale of the SAM variability, which moved from 32 to 64 months during 1990s. This change generates a common energy peak for the SAM and ENSO with a lagged in phase relationship between the signals, possibly influencing the behaviour of the surface heat fluxes.

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Southern Ocean Mixed‐Layer Seasonal and Interannual Variations From Combined Satellite and In Situ Data

Cited by 51 publications

References 44 publications

Three‐Dimensional Ageostrophic Motion and Water Mass Subduction in the Southern Ocean

Three‐Dimensional Ageostrophic Motion and Water Mass Subduction in the Southern Ocean

Impact of ocean mixed‐layer depth initialization on the simulation of tropical cyclones over the Bay of Bengal using the WRF‐ARW model

Different Behaviours of the Ross and Weddell Seas Surface Heat Fluxes in the Period 1972–2015

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