When it rains over the ocean, does it make the floor water extra buoyant? Scientists have lengthy assumed so as a result of rainwater is contemporary and freshwater is lighter than seawater. However, a brand new study by researchers on the University of Washington in Seattle, US, has discovered that the reply is definitely extra sophisticated. The study was printed in July.
Rain within the tropics typically comes with giant clouds and chilly, dry air known as chilly swimming pools. These chilly swimming pools can really cool the ocean’s floor by blocking daylight and growing the switch of warmth from the water to the air. So as a substitute of creating the floor lighter, which might assist combine waters within the ocean, rain generally makes the floor heavier and extra secure.
The researchers used knowledge from 22 buoys throughout the equatorial oceans that measure rainfall, sea floor temperature, wind velocity, and warmth switch. The duo analysed greater than 31,000 hours of rainfall occasions from this knowledge, specializing in the buoyancy flux, which mixes the consequences of warmth and freshwater. If the buoyancy flux is optimistic, the ocean floor is much less secure and promotes mixing.
They discovered that in gentle rain (0.2-4 mm/hr), buoyancy flux was typically optimistic, which means it tends to destabilise the ocean and promote mixing. But throughout heavier rain, the buoyancy flux was nearly at all times adverse, which means the ocean floor was extra secure. This is as a result of heavy rain is normally accompanied by stronger chilly swimming pools that pull warmth out of the ocean extra successfully.
The study additionally discovered that at night time, rainfall was extra more likely to trigger instability than throughout the day. Geography additionally mattered: the researchers recognized a ‘cold rain zone’, primarily within the western Pacific and Indian Oceans, the place rain was related to extra warmth loss, and a ‘hot rain zone’ within the central Pacific the place warmth loss was much less intense.
These variations had been tied to sea floor temperatures and the energy of the accompanying atmospheric downdrafts.
“The sky doesn’t just water the sea, it alters its balance,” Dipanjan Chaudhuri, a postdoc on the Applied Physics Laboratory on the University of Washington and the study’s first writer, mentioned. “This matters because ocean mixing plays a key role in regulating the climate by transporting heat, carbon, and nutrients. Any gaps in understanding how rainfall affects the ocean can lead to inaccuracies in weather and climate predictions.”
