Abstract Shortwave radiation penetrating through the bottom of the mixed layer (ML) (Qpen) significantly modulates sea surface temperature (SST) variability. Here, we show that summertime Qpen is projected to increase by 3.9 (3.7) ± 1.9 (1.6) W m−2 in the northern (southern) mid‐latitude oceans under the high emission scenario (SSP5‐8.5) during 2051–2100 compared to the historical simulation during 1951–2000. This increase is driven primarily by a ML shoaling, and secondarily by a reduction of chlorophyll in summer. The latter exerts a pronounced impact on Qpen, resulting from higher sensitivity of Qpen to seasonal chlorophyll reduction in mid‐latitude oceans due to the shoaling of the summertime ML. Furthermore, the enhanced Qpen reduces the magnitude of SST tendency by 25.3% in summer, thereby weakening summertime month‐to‐month SST tendency in these regions. These results highlight the critical role played by Qpen in ocean warming, requiring a better representation of radiation penetration in climate models.
Observations from the Little Bunker
Last updated: October 16, 2025 02:57 AM
Atmospheric CO₂
424.4 ppm
+18.2
ppm/year
Atmospheric CH₄
1933.54 ppb
+12.29
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
World Population
8.1 billion
+67
million/year