Records of Paleo Sea Level

Going back ~3 million years to the middle Pliocene, there is robust evidence indicating that sea level was higher than today (but did not exceed 20 m higher; IPCC AR5 Chapter 5), but much uncertainty remains about the mechanism responsible.  During Marine Isotope Stage 11 (424,000 years BP), another warm interglacial period, sea level was as much as 15 m higher than present, corresponding to temperatures ~1.5-2.0°C warmer than pre-industrial.  This sea level increase requires a loss of all if not most of  both the Greenland Ice Sheet (GIS) and West Antarctic Ice Sheet (WAIS) and a significant reduction in the East Antarctic Ice Sheet (EAIS).  During the last interglacial period (~130,000 years BP) temperatures were 1-2°C warmer than pre-industrial, and GMSL was at least 6 m higher than modern.  The individual contributions from large ice masses are also better constrained for this most recent interglacial period.  During the late Holocene (~7000-3000 years BP) increasing global temperatures likely drove the 2-3 m increase in sea level to near modern values. 

 

Instrumental Period (~1700-2012 CE)

Our best records are from the Instrumental period (~1700-2012 CE), consisting mostly of tide gauge measurements and, since the 1990s, satellite altimetry.  From these records there is high confidence that the rate of sea level rise has increased over the last two centuries and it is likely that GMSL has accelerated since the 1900’s.  Current data reports the GMSL rise is ~1.7 mm/yr between 1901 and 2010 for a total sea level rise of ~0.19 m over the same time period.  However, more recent data suggest that GMSL is rising at ~3.2 mm/yr over the 1993-2012 period (Fig. 13.3)