Observed Global Increases in Tropical Cyclone‐Induced Ocean Cooling and Primary Production

Abstract

Tropical cyclones provide an important source of ocean mixing, bringing cold, nutrient‐rich water to the surface and triggering phytoplankton blooms. Here, we show significant increases in global tropical cyclone‐induced sea surface temperature cooling and surface chlorophyll‐a concentration of 0.05°C and 3.7 × 10−3 mg m−3 per decade over the past 20–35 years. The trends have been driven primarily by an increase in the intensity of strong tropical cyclones. The increase in chlorophyll‐a concentration has been, on average, 1.6% per decade in oligotrophic areas during the tropical cyclone season, in contrast to a decrease of 0.1% per decade during the other months. This tropical cyclone‐induced increase has partially mitigated the overall decline in primary production under climate change.

Recent tropical cyclone changes inferred from ocean surface temperature cold wakes

“…However, the observed sea surface cooling observation may also experience temporal heterogeneities due to the improvement of observational techniques, which is a similar issue as the best track has. Our finding of the enhance TC-induced sea surface cooling is in line with a recent study reporting a cooling trend of TC wakes by about 0.05 °C per decade 23 , which was also validated with the microwave satellite SST data set. This cooling trend is about half of what we find here, but all TC positions were considered, not just at the LMI as here.…”

“…As the cooling increases with TC intensity and the LMI trend is more than double the mean intensity trend, our larger cooling trends are understandable. This study makes the first attempt to infer the wind speed trend, but the previous study 23 did show a high spatial correlation of the cooling enhancement and TC intensity increase.…”

“…One example is TC-induced SST cooling or cold wake 19 , the amplitude of which is modulated primarily by three factors: the TC intensity 20 , translation speed 21 and upper ocean thermal structure 22 . A cooling of the ocean wakes caused by TCs has been recently reported 23 , which is found to be spatially correlated with TC intensity changes, but this observed change has not been used to infer the TC intensity trend. It has also been shown that the size of cold wakes and TC size can be related 24 .…”

Global Estimate of Tropical Cyclone‐Induced Diapycnal Mixing and Its Links to Climate Variability

“…The 5-day mean temperature and salinity data are obtained from the Simple Ocean Data Assimilation version 3.7.2 (SODA v3.7.2) with a horizontal resolution of 0.5° × 0.5° and with 50 levels. Several articles have also verified that the reanalysis data (SODA) can be used to calculate the TC-induced vertical diffusivity such as Da et al (2021). The initial mixed layer depth is calculated according to de Boyer Montégut et al (2007), and the potential density gradient below the mixed layer is calculated as the difference between mixed layer base and 50 m below mixed layer base in the pre-storm (Balaguru et al, 2015).…”

Physical and Biochemical Responses to Sequential Tropical Cyclones in the Arabian Sea

“…As global warming develops, the number of extremely severe TCs is likely to increase in the AS, meaning that the upper ocean has a more intense response to TCs [33]. The chl-a concentrations associated with TC activities have been increasing steadily over the past 20-35 years; this increase is mainly attributed to the increasing intensities of strong TCs [34]. The increasing trend in primary production associated with TC activities can partially mitigate the declining trend of ocean productivity under the background of global warming.…”