Winter convection in the North Atlantic and male sperm whales' slow clicks show matter and sound traveling along different routes through the ocean.
Science··Midday
From the surface to below a thousand metres
In the research reported by Phys.org, Argo floats in the Labrador and Irminger seas measured chlorophyll near a thousand metres between 2014 and 2017. This pigment belongs to the sunlit surface layer and was expected to break down before reaching such depth. According to the paper published by Science Advances on 31 July, cold, strong winter winds cool surface water; the denser water sinks rapidly while carrying living microalgae and organic debris below 1,000 metres. This route operates faster than the slow gravitational settling of particles. During strong winters, the mechanism reportedly supplies 30 percent to 50 percent of the organic particles found between 500 m and 2,000 m, with its contribution roughly doubling in the harshest winters. A comparison of satellite observations at the surface with particle properties at 1,000 metres found the transported material rich in energy. The findings describe a seasonal passage between the surface and deep ocean that can transfer living material faster than expected.[1]
Long-range clicks in deep water
In the second report, an international team measured slow clicks with suction-cup sound recording tags attached to male sperm whales off the Seychelles, Sri Lanka, Norway and Scotland. These low-frequency communication sounds differ from the echolocation clicks used to find prey. According to the paper published in the Annals of the New York Academy of Sciences on 18 May, source levels exceed 200 decibels referenced to 1 micropascal; the report describes this as the loudest communication sound measured in any mammal. Under typical deep-water conditions, the estimated active space is about 70 km. The team proposes that a larger male's larger nose may produce a lower frequency, allowing the sound to carry information about body size. Researchers stress that the clicks' behavioural function and other whales' responses remain unknown. Temperature, salinity, depth and shipping noise narrow their reach; amid heavy shipping noise, the signal may be limited to a few kilometres.[2]
Two movements within ocean conditions
The reports follow two ocean transfers along different directions. In the North Atlantic work, surface water cooled and made denser during winter moves microalgae and organic particles vertically into depth; Argo floats detect chlorophyll associated with the surface near a thousand metres. In the whale work, low-frequency clicks can spread horizontally for tens of kilometres through deep water; tags attached to whales directly follow the sound source and rhythm. Each range is presented together with surrounding conditions. Convective transfer grows during strong winter mixing, while sound reach varies with temperature, salinity, depth and human shipping noise. One report describes organic material passing from the surface ecosystem into deep layers; the other describes the reach of male sperm whales' communication sounds through water. Taken together, the deep ocean appears as an active setting in which moving water and a changing acoustic environment form part of the route and range of what travels through it.[1], [2]
