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.
Plain Language Summary
Tropical cyclones (TCs) associated with strong wind can produce mixing in the upper ocean, bringing cold and nutrient‐rich water in the subsurface to the surface and trigger photosynthesis. Therefore, they often leave trails on the surface of cold water and high Chlorophyll‐a concentration, which can be observed from satellites. It is unknown how these interactions between TCs and the upper ocean change under global warming. In this study, based on satellite observations of sea surface temperature and Chlorophyll‐a concentration over the past 20–35 years, we discover that ocean surface cooling and Chlorophyll‐a concentration associated with TC activities have been increasing steadily. These changes are mainly attributed to the increasing intensity of strong (cat. 1–5) TCs. The increasing trend in primary production associated with TC activities can partially mitigate the declining trend of ocean productivity under global warming.
Key Points
Global tropical cyclone induced surface cooling and primary production has been increasing over the past 35 years
The increasing trends of surface cooling and primary production are mainly attributed to increasing tropical cyclone intensity
The decline in primary production induced by global warming has been partially negated by tropical cyclones in oligotrophic waters
