Sea level rise has slowed... temporarily

Over the past 10 years at least, sea levels have been rising relatively steadily. This is mostly due to melting glaciers and ice sheets, and is a natural -- if detrimental -- consequence of global warming. The rate of ocean level rise has been a little over 3 millimeters per year (about 1/8th of an inch per year)... until last year. The rate of increase suddenly reversed itself in 2010, and the sea levels actually dropped a bit, by about 6 mm. What happened?