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Global Spatial and Temporal Variability of the Oceanic Cool Skin Effect.

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Title:	Global Spatial and Temporal Variability of the Oceanic Cool Skin Effect.
Authors:	Jia, Chong¹ (AUTHOR) chong.jia@earth.miami.edu, Minnett, Peter J.¹ (AUTHOR)
Source:	Journal of Geophysical Research. Oceans. Apr2026, Vol. 131 Issue 4, p1-24. 24p.
Subject Terms:	Ocean temperature, Seasonal temperature variations, Spatial variation, Infrared radiometry, Sea surface microlayer
Abstract:	The oceanic cool skin effect is characterized by a temperature depression between the ocean's submillimeter thermal skin layer (SSTskin) and the underlying water (SSTdepth). This study evaluates the ability of the widely used Fairall et al. (1996), https://doi.org/10.1029/95jc03190 model (F96) to simulate the cool skin effect using surface forcing data from the Modern‐Era Retrospective analysis for Research and Applications, Version 2 (MERRA‐2), validated against high‐accuracy infrared radiometric measurements from the Marine‐Atmospheric Emitted Radiance Interferometer (M‐AERI) and the Infrared Sea Surface Temperature Autonomous Radiometer (ISAR) collected during research cruises spanning diverse oceanic regions. Results show that F96 model simulations driven by MERRA‐2 inputs generally match the observed skin effects, with mean biases of −0.03 to −0.04 K and standard deviations ∼0.1 K, attributed primarily to uncertainties in humidity, longwave radiative flux, and wind speed. A 24‐year global analysis (2000–2023) revealed a mean cool skin effect of approximately −0.2 K, with pronounced spatial and seasonal variability. Strongest cooling (−0.3 K or more) occurs in regions such as western boundary currents during colder months, while the Southern Ocean shows much weaker skin effects (−0.1 K) due to persistent high wind speeds and reduced net heat loss. These results suggest that the commonly applied constant correction of −0.17 K in satellite SSTskin retrievals does not accurately represent the true magnitude and variability of the cool skin effect. A more accurate correction scheme incorporating latitude and seasonal dependence is recommended to improve the accuracy of satellite‐derived SSTskin fields, and better support climate model applications. Plain Language Summary: The ocean's surface is usually slightly cooler than the water just beneath it, a difference known as the cool skin effect. This small but persistent temperature gradient affects how heat and gases are exchanged between the ocean and the atmosphere and influences satellite measurements of sea surface temperature (SST). Using a physics‐based model and global meteorological data from MERRA‐2, this study examined the global and seasonal variability of the cool skin effect from 2000 to 2023. Model results were evaluated against highly accurate infrared radiometer measurements collected from research vessels. The simulations show that the global average cool skin effect is about −0.2 K, slightly stronger than the −0.17 K correction commonly applied in satellite SST products. The strength of cooling varies with region and season, being strong in western boundary currents during winter and weak in the windy Southern Ocean, suggesting that spatially adaptive corrections are needed for greater accuracy. Key Points: F96 model driven by MERRA‐2 data reproduces the observed cool skin effect with small biases (−0.03 to −0.04 K) and 0.1 K standard deviationGlobal simulations of the cool skin are about −0.2 K, strong (−0.3 K) in western boundary currents and weak (−0.1 K) in the Southern OceanA constant correction of −0.17 K in satellite SSTskin retrievals is suboptimal; a latitude‐ and season‐dependent adjustment is recommended [ABSTRACT FROM AUTHOR]
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Database:	GreenFILE

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Abstract:	The oceanic cool skin effect is characterized by a temperature depression between the ocean's submillimeter thermal skin layer (SSTskin) and the underlying water (SSTdepth). This study evaluates the ability of the widely used Fairall et al. (1996), https://doi.org/10.1029/95jc03190 model (F96) to simulate the cool skin effect using surface forcing data from the Modern‐Era Retrospective analysis for Research and Applications, Version 2 (MERRA‐2), validated against high‐accuracy infrared radiometric measurements from the Marine‐Atmospheric Emitted Radiance Interferometer (M‐AERI) and the Infrared Sea Surface Temperature Autonomous Radiometer (ISAR) collected during research cruises spanning diverse oceanic regions. Results show that F96 model simulations driven by MERRA‐2 inputs generally match the observed skin effects, with mean biases of −0.03 to −0.04 K and standard deviations ∼0.1 K, attributed primarily to uncertainties in humidity, longwave radiative flux, and wind speed. A 24‐year global analysis (2000–2023) revealed a mean cool skin effect of approximately −0.2 K, with pronounced spatial and seasonal variability. Strongest cooling (−0.3 K or more) occurs in regions such as western boundary currents during colder months, while the Southern Ocean shows much weaker skin effects (−0.1 K) due to persistent high wind speeds and reduced net heat loss. These results suggest that the commonly applied constant correction of −0.17 K in satellite SSTskin retrievals does not accurately represent the true magnitude and variability of the cool skin effect. A more accurate correction scheme incorporating latitude and seasonal dependence is recommended to improve the accuracy of satellite‐derived SSTskin fields, and better support climate model applications. Plain Language Summary: The ocean's surface is usually slightly cooler than the water just beneath it, a difference known as the cool skin effect. This small but persistent temperature gradient affects how heat and gases are exchanged between the ocean and the atmosphere and influences satellite measurements of sea surface temperature (SST). Using a physics‐based model and global meteorological data from MERRA‐2, this study examined the global and seasonal variability of the cool skin effect from 2000 to 2023. Model results were evaluated against highly accurate infrared radiometer measurements collected from research vessels. The simulations show that the global average cool skin effect is about −0.2 K, slightly stronger than the −0.17 K correction commonly applied in satellite SST products. The strength of cooling varies with region and season, being strong in western boundary currents during winter and weak in the windy Southern Ocean, suggesting that spatially adaptive corrections are needed for greater accuracy. Key Points: F96 model driven by MERRA‐2 data reproduces the observed cool skin effect with small biases (−0.03 to −0.04 K) and 0.1 K standard deviationGlobal simulations of the cool skin are about −0.2 K, strong (−0.3 K) in western boundary currents and weak (−0.1 K) in the Southern OceanA constant correction of −0.17 K in satellite SSTskin retrievals is suboptimal; a latitude‐ and season‐dependent adjustment is recommended [ABSTRACT FROM AUTHOR]
ISSN:	21699275
DOI:	10.1029/2025JC023652