SummaryThe ocean is home to myriad small planktonic organisms that underpin the functioning of marine ecosystems. However, their spatial patterns of diversity and the underlying drivers remain poorly known, precluding projections of their responses to global changes. Here we investigate the latitudinal gradients and global predictors of plankton diversity across archaea, bacteria, eukaryotes, and major virus clades using both molecular and imaging data from Tara Oceans. We show a decline of diversity for most planktonic groups toward the poles, mainly driven by decreasing ocean temperatures. Projections into the future suggest that severe warming of the surface ocean by the end of the 21st century could lead to tropicalization of the diversity of most planktonic groups in temperate and polar regions. These changes may have multiple consequences for marine ecosystem functioning and services and are expected to be particularly significant in key areas for carbon sequestration, fisheries, and marine conservation.Video Abstract

Periodic features observed on the ocean surface from the Earth Resources Technology Satellite 1 have been interpreted as surface slicks due to internal wave packets. They appear to be generated at the edge of the continental shelf by semidiurnal and diurnal tidal actions and propagate shoreward. Nonlinear effects apparently distort the wave packets as they progress across the shelf. This observational technique constitutes a new tool for delineating two dimensions of the internal wave field under certain limited conditions.

Internal waves on the continental shelf off New York have been observed from ship and the ERTS‐1 spacecraft, and positive correlations made between surface and subsurface measurements of temperature, acoustic volume reflectivity, and surface slicks. The spacecraft imagery senses the quasi‐periodic variations in surface optical reflectivity induced by the internal waves. The waves appear to be tidally generated at the shelf edge and occur intermittently in packets, which propagate shoreward and disappear in water near 50‐m depth.

Preliminary analysis of radar altimeter data indicates that the instrument has met its specifications for measuring spacecraft height above the ocean surface (+/- 10 centimeters) and significant wave height (+/- 0.5 meter). There is ample evidence that the radar altimeter, having undergone development through three earth orbit missions [Skylab, Geodynamics Experimental Ocean Satellite 3 (GEOS-3), and Seasat], has reached a level of precision that now makes possible its use for important quantitative oceanographic investigations and practical applications.