Air-Sea Latent Heat Flux Anomalies Induced by Oceanic Submesoscale Processes: An Observational Case Study

The classical theory predicts that a geostrophically balanced mesoscale eddy can cause a sea surface temperature (SST) anomaly related to Ekman pumping. Previous studies show that an eddy-induced SST anomaly can result in a sea surface latent heat flux (LH) anomaly at a maximum magnitude of ∼O(10) Wm–2, decaying radially outward from the center to the margin. In this study, we investigate the LH anomalies associated with submesoscale processes within a cyclonic eddy for the first time using recent satellite-ship-coordinated air-sea observations in the South China Sea. Unbalanced submesoscale features can be identified as submesoscale SST fronts. Along the ship track, the SST strikingly decreases by 0.5°C within a horizontal distance of ∼1.5 km and increases quickly by 0.9°C with a spatial interval of ∼3.6 km. The along-track SST is decomposed into three parts: large-scale south-north fronts and anomalies induced by mesoscale and submesoscale motions. Our analysis shows that the amplitude of the LH anomaly induced by the mesoscale SST anomaly is 12.3 Wm–2, while it is 14.3 Wm–2 by unbalanced submesoscale motions. The mean (maximum) spatial gradient of the submesoscale LH anomalies is 1.7 (75.7) Wm–2km–1, which is approximately 1.5 times those (1.2 and 59.9 Wm–2km–1) in association with mesoscale eddies. The spectra of LH and SST anomalies show similar peaks at ∼15 km before sloping down with a power law between k–2 and k–3, indicating the underlying relationship between the LH variance and submesoscale processes.

[1]  Guihua Wang,et al.  Diurnal variation in surface latent heat flux and the effect of diurnal variability on the climatological latent heat flux over the tropical oceans , 2021, Journal of Physical Oceanography.

[2]  Weidong Yu,et al.  Observed Extreme Air–Sea Heat Flux Variations during Three Tropical Cyclones in the Tropical Southeastern Indian Ocean , 2021, Journal of Climate.

[3]  Xiangzhou Song.  The Importance of Including Sea Surface Current when Estimating Air–Sea Turbulent Heat Fluxes and Wind Stress in the Gulf Stream Region , 2020 .

[4]  D. Menemenlis,et al.  High‐Frequency Submesoscale Motions Enhance the Upward Vertical Heat Transport in the Global Ocean , 2020, Journal of Geophysical Research: Oceans.

[5]  Ge Chen,et al.  Characterization of Sea Surface Temperature and Air‐Sea Heat Flux Anomalies Associated With Mesoscale Eddies in the South China Sea , 2020 .

[6]  D. Menemenlis,et al.  Enhanced upward heat transport at deep submesoscale ocean fronts , 2019, Nature Geoscience.

[7]  Adrian P. Martin,et al.  Wind‐Forced Symmetric Instability at a Transient Mid‐Ocean Front , 2019, Geophysical Research Letters.

[8]  C. A. Clayson,et al.  Diurnal Surface Flux Variability Over Western Boundary Currents , 2019, Geophysical Research Letters.

[9]  Lisan Yu.  Global Air-Sea Fluxes of Heat, Fresh Water, and Momentum: Energy Budget Closure and Unanswered Questions. , 2019, Annual review of marine science.

[10]  Dimitris Menemenlis,et al.  Ocean submesoscales as a key component of the global heat budget , 2018, Nature Communications.

[11]  D. Marshall,et al.  Submesoscale Instabilities in Mesoscale Eddies , 2017 .

[12]  J. McWilliams,et al.  Stimulated Imbalance and the Enhancement of Eddy Kinetic Energy Dissipation by Internal Waves , 2017 .

[13]  James C. McWilliams,et al.  Submesoscale currents in the ocean , 2016, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[14]  Christian E. Buckingham,et al.  Open-Ocean Submesoscale Motions: A Full Seasonal Cycle of Mixed Layer Instabilities from Gliders , 2016 .

[15]  Jonathan Gula,et al.  Seasonality in submesoscale turbulence , 2015, Nature Communications.

[16]  Guilherme P. Castelão,et al.  The signature of mesoscale eddies on the air‐sea turbulent heat fluxes in the South Atlantic Ocean , 2015 .

[17]  Larry W. O'Neill,et al.  Satellite Observations of Mesoscale Eddy-Induced Ekman Pumping , 2015 .

[18]  Bo Qiu,et al.  Impact of oceanic-scale interactions on the seasonal modulation of ocean dynamics by the atmosphere , 2014, Nature Communications.

[19]  Y. Sasai,et al.  Seasonal Mesoscale and Submesoscale Eddy Variability along the North Pacific Subtropical Countercurrent , 2014 .

[20]  H. Hersbach,et al.  On the exchange of momentum over the open ocean , 2013 .

[21]  Reto Knutti,et al.  Imprint of Southern Ocean eddies on winds, clouds and rainfall , 2013 .

[22]  T. Özgökmen,et al.  Seasonality of the submesoscale dynamics in the Gulf Stream region , 2013, Ocean Dynamics.

[23]  E. Chassignet,et al.  The ocean's response to North Atlantic Oscillation variability , 2013 .

[24]  A. Czaja,et al.  The observed signature of mesoscale eddies in sea surface temperature and the associated heat transport , 2012 .

[25]  Lisan Yu,et al.  High-latitude contribution to global variability of air–sea sensible heat flux , 2012 .

[26]  D. Chelton,et al.  Global observations of nonlinear mesoscale eddies , 2011 .

[27]  Dudley B. Chelton,et al.  Coupled ocean-atmosphere interaction at oceanic mesoscales , 2010 .

[28]  Taka Ito,et al.  Anthropogenic carbon dioxide transport in the Southern Ocean driven by Ekman flow , 2010, Nature.

[29]  James W. Hurrell,et al.  North Atlantic climate variability: The role of the North Atlantic Oscillation , 2009 .

[30]  K. Trenberth,et al.  Earth's Global Energy Budget , 2009 .

[31]  W. Liu,et al.  Warm ocean anomaly, air sea fluxes, and the rapid intensification of tropical cyclone Nargis (2008) , 2009 .

[32]  Lisan Yu,et al.  Global Variations in Oceanic Evaporation (1958–2005): The Role of the Changing Wind Speed , 2007 .

[33]  Dongxiao Wang,et al.  Interannual variability of the South China Sea associated with El Niño , 2006 .

[34]  M. Mcphaden,et al.  Mixed Layer Heat Balance on Intraseasonal Time Scales in the Northwestern Tropical Atlantic Ocean , 2005 .

[35]  P. Oke,et al.  Oceanic Response to Changes in the Latitude of the Southern Hemisphere Subpolar Westerly Winds , 2004 .

[36]  E. F. Bradley,et al.  Bulk Parameterization of Air–Sea Fluxes: Updates and Verification for the COARE Algorithm , 2003 .

[37]  M. Visbeck,et al.  Synchronous Variability in the Southern Hemisphere Atmosphere, Sea Ice, and Ocean Resulting from the Annular Mode* , 2002 .

[38]  James W. Hurrell,et al.  North Atlantic climate variability: phenomena, impacts and mechanisms , 2001 .

[39]  T. Qu.  Role of ocean dynamics in determining the mean seasonal cycle of the South China Sea surface temperature , 2001 .

[40]  D. Chelton,et al.  Geographical Variability of the First Baroclinic Rossby Radius of Deformation , 1998 .

[41]  J. Carton,et al.  Annual cycle of sea surface temperature in the tropical Atlantic Ocean , 1997 .

[42]  Daniel R. Cayan,et al.  Latent and sensible heat flux anomalies over the northern oceans : driving the sea surface temperature , 1992 .

[43]  P. Falkowski,et al.  Role of eddy pumping in enhancing primary production in the ocean , 1991, Nature.

[44]  Stuart D. Smith.  Coefficients for sea surface wind stress, heat flux, and wind profiles as a function of wind speed and temperature , 1988 .

[45]  W. Large,et al.  Open Ocean Momentum Flux Measurements in Moderate to Strong Winds , 1981 .

[46]  W. Liu,et al.  Bulk Parameterization of Air-Sea Exchanges of Heat and Water Vapor Including the Molecular Constraints at the Interface , 1979 .

[47]  F. W. Murray,et al.  On the Computation of Saturation Vapor Pressure , 1967 .

[48]  Craig M. Lee,et al.  Symmetric Instability, Inertial Oscillations, and Turbulence at the Gulf Stream Front , 2016 .

[49]  Benguela Ninos,et al.  Interannual Variability in the , 2010 .

[50]  C. Wunsch,et al.  Ocean Circulation Kinetic Energy: Reservoirs, Sources, and Sinks , 2009 .