A NEW PROBABILISTIC ESTIMATE OF GLOBAL AND LOCAL SEA LEVELS OVER THE 20TH CENTURY

Our understanding of sea level over the 20^th century, both globally and locally, is limited to the information derived from spatially sparse and temporally incomplete tide gauge records. An additional complicating factor arises because local sea level can deviate from the global mean value due to a variety of processes including ongoing sea-level changes due to the last ice age, ocean circulation and ocean-atmosphere interactions, and rapid melting of present day land-based ice. Using two probabilistic techniques that make use of the physics-based and model-derived geometries of the underlying sea-level processes responsible for the observed changes, we have estimated a rate of global mean sea level (GMSL) rise of 1.2 +/- 0.2 mm/yr over the time period 1901-1990. In addition to estimating GMSL rise, we also reconstruct sea-level time histories at both a suite of specific tide gauge sites and on a global grid. Our reconstructed sea-level time series, which agree well with the observations, allow us to examine sea level along data-sparse coastlines where a significant portion of the global population is situated. Understanding past changes in coastal sea level is a critical precondition for robustly assessing future hazards.