Atlantic Ocean with steric effects

Lively Data : September 22, 2006

Steric effects are one of the most important contributation to sea surface height variability; they are due to the air differences in temperature between summer and winter. Let's have a look on ERS-2 satellite observations, in 2002 for example:

Monthly averages of sea level anomalies, North Atlantic: February 2002 (left), October 2002 (middle), and differences between the two maps (right).
Dataset: SSALTO/DUACS near-real time Maps of Sea Level Anomalies ; variable: MSLA Low Resolution ERS-2.
Choose "define variable" in the left menu, this option let you compute some statistics with data. Choose "average", define your temporal period (January 30 to February 27, 2002 then October 02 to October 30, 2002) and finally your area (20°E-80°W; 0-70°N).
You can modify color palettes in the output options. You can also compute and visualize the differences between the two maps by using the "compare two" menu, with the "comparison plot" option.

In October, MSLA are higher than in February: the second image is a signature of ocean expansion due to the rising temperatures during Summer, as the first one represent the decreasing sea level after winter (and lower temperatures). Differences can reach 30 cm.