Bryan Killett is a physicist working on the Gravity Recovery And
Climate Experiment (GRACE) for NASA's Jet Propulsion Laboratory.
GRACE is a joint mission of NASA and the German Aerospace Center
which collects satellite data to learn about Earth's changing
gravity field, specifically the high frequency changes
associated with ocean tides. As the high tide comes in, more
water is present, so gravity in that location is temporarily
strengthened. These changes are detected with GRACE and used to
improve ocean tide models. Dr. Killett provides the open source
(GPLv3) code used to process GRACE data on his home page. Bryan
has agreed to take a break from measuring gravity fields and
answer your questions about GRACE and the climate changes it has
revealed. Feel free to ask as many as you like but please
confine your questions to one per post.