Ángel Amores

Quantifying anthropogenic and natural contributions to thermosteric sea level rise

Changes in thermosteric sea level at decadal and longer time scales respond to anthropogenic forcing and natural variability of the climate system. Disentangling these contributions is essential to quantify the impact of human activity in the past and to anticipate thermosteric sea level rise under global warming. Climate models, fed with radiative forcing, display a large spread of outputs with limited correspondence with the observationally based estimates of thermosteric sea level during the last decades of the twentieth century. Here we extract the common signal of climate models from Coupled Model Intercomparison Project Phase 5 using a signal-to-noise maximizing empirical orthogonal function technique for the period 1950–2005. Our results match the observed trends, improving the widely used approach of multimodel ensemble averaging. We then compute the fraction of the observed thermosteric sea level rise of anthropogenic origin and conclude that 87% of the observed trend in the upper 700 m since 1970 is induced by human activity.

Signature of mesoscale eddies in satellite sea surface salinity data

A persistent signature of coherent mesoscale eddies in sea surface salinity (SSS) is revealed by analyzing the relationship between satellite SSS and sea surface height (SSH) variability in an eddy-following reference frame. Our analysis focuses on mid-ocean eddies in two representative regions, the southern Indian Ocean and the North Atlantic subtropical gyre. The resulting composite averages reveal a clear signature of mesoscale eddies in satellite SSS with typical SSS anomalies of 0.03-0.05 psu. The spatial structure of eddy-induced SSS perturbations can be characterized as a superposition of a dipole structure, arising from horizontal advection of the background SSS gradient by eddy velocity field, and a monopole structure related to the eddy core. The observed relationships between SSS and SSH anomalies are used to provide a regional assessment of the role of mesoscale eddies in the ocean freshwater transport in the North Atlantic subtropical gyre. This article is protected by copyright. All rights reserved.