Sea level and climate: measurements and causes of changes

We review present‐day observations of sea level change and variability at global and regional scales, focusing on the altimetry era starting in the early 1990s. Over the past ∼18‐years, the rate of global mean sea level rise has reached 3.3 ± 0.4 mm/year, nearly twice that of the previous decades, although the observed larger sea level rise rate may be influenced by decadal or longer variations in the ocean. Moreover, sea level rates are not geographically uniform; in some regions like the tropical western Pacific, rates are up to 3–4 times higher than the global mean rate. We next discuss the climate‐related components of the global mean sea level rise. Over the last ∼18‐years, ocean thermal expansion contributes about one third to the observed rise while total land ice (glacier melting plus ice sheet mass loss) contribute the other two third. The spatial trend patterns evidenced over the altimetry period mostly result from nonuniform steric sea level changes (effects of ocean temperature and salinity), largely caused by wind‐driven ocean circulation changes. Such patterns are not stationary but oscillate through time on decadal/multidecadal time scale, in response to natural modes of the coupled ocean‐atmosphere system. We close up this review by briefly discussing future (21st century) sea level rise. Current limited knowledge of the future evolution of the mass balance of the Greenland and Antarctica ice sheets leads to high uncertainty on the global mean sea level rise expected for the next 50–100 years. WIREs Clim Change 2011 2 647–662 DOI: 10.1002/wcc.139 This article is categorized under: Paleoclimates and Current Trends > Earth System Behavior