Global mapping of 10-day differences of temperature and salinity in the intermediate layer observed with Argo floats

The authors examine small-scale spatiotemporal variability of the layer nearly 2000-m depth, which is the “bottom” of the present Argo observation system, using all of available Argo float data. The 10-day change, Δ T 10 , is defined as the difference of temperature between two successive observations with an interval of nearly 10 days for each individual float at an isobaric surface. |Δ T 10 | is large along the western boundary currents at 1000 dbar, and becomes less remarkable with depth. At 1950 dbar, mean |Δ T 10 | is noticeable in the northeastern Atlantic Ocean (NEAO), the Argentine basin, and the northwestern Indian Ocean. In the Southern Ocean, large |Δ T 10 | is localized in some areas located over the ridges or leeward of the plateau. Basically, Δ T 10 at isobaric surfaces is accounted for by the heave component, but the spiciness component is dominant or comparable to the other in the NEAO and the Argentine basin. Δ T 10 decreases with depth monotonically most of the world, suggesting that wind energy input is attenuated with depth. In some areas in the Southern Ocean, however, the vertical profile of |Δ T 10 | implies enhanced bottom-induced turbulence. |Δ T 10 | peaks at 1300 dbar in the NEAO, corresponding to the spread of the Mediterranean Outflow Water. |Δ T 10 | is smaller in the Pacific Ocean compared with the other oceans, but is enhanced along the equator, the Kuroshio and its Extension, the Kuril, Aleutian, Hawaii, and Mariana Islands, and the Emperor Seamount Chain.