Reassessment of 20th century global mean sea level rise

Abstract

The rate at which global mean sea level (GMSL) rose during the 20th century is uncertain, with little consensus between various reconstructions that indicate rates of rise ranging from 1.3 to 2 mm·y −1 . Here we present a 20th-century GMSL reconstruction computed using an area-weighting technique for averaging tide gauge records that both incorporates up-to-date observations of vertical land motion (VLM) and corrections for local geoid changes resulting from ice melting and terrestrial freshwater storage and allows for the identification of possible differences compared with earlier attempts. Our reconstructed GMSL trend of 1.1 ± 0.3 mm·y −1 (1σ) before 1990 falls below previous estimates, whereas our estimate of 3.1 ± 1.4 mm·y −1 from 1993 to 2012 is consistent with independent estimates from satellite altimetry, leading to overall acceleration larger than previously suggested. This feature is geographically dominated by the Indian Ocean-Southern Pacific region, marking a transition from lower-than-average rates before 1990 toward unprecedented high rates in recent decades. We demonstrate that VLM corrections, area weighting, and our use of a common reference datum for tide gauges may explain the lower rates compared with earlier GMSL estimates in approximately equal proportion. The trends and multidecadal variability of our GMSL curve also compare well to the sum of individual

Observed Sea-Level Changes along the Norwegian Coast

“…For 1960 to 2010, we calculate the weighted average sea-level rise along the Norwegian coast as 2.0 ± 0.6 mm/year. This rate of rise is similar to the rate of 20th century GMSL rise given in the fifth assessment report of the Intergovernmental Panel on Climate Change [33], but almost two times recent global estimates reported in [34] and [2].…”

“…The coastline is complex with fjords, islands, reefs, ocean currents, and significant variations in the tidal regime. Relative sea-level (RSL) rates vary along the coast and differ considerably from the rate of global mean sea-level rise (see, e.g., [2] for an overview of rates estimated from global mean sea level (GMSL) reconstructions). The Norwegian Mapping Authority (NMA) operates an array of 23 tide gauges over the region that continuously record water level heights (e.g., the tides, extreme sea levels, and changes to mean sea level) (see Figure 1 and Table 1).…”

Impact of North Atlantic Teleconnection Patterns on Northern European Sea Level

“…Therefore, even a future small shift in the position of the North Atlantic meridional pressure dipole may lead to large effects on European sea levels and hence enhanced flood risk, further underlining that a correct representation of these atmospheric teleconnections in climate models is a prerequisite for projecting sea level change, in particular, on the regional scale. Not least since the variability caused by the interaction of the teleconnection patterns demonstrated herein are on the order of magnitude as the centennial global mean sea level change [1]. Furthermore, on a national level these combinations may act as a guideline of which atmospheric patterns and concomitant teleconnection states are important.…”

“…Global mean sea level has been accelerating from rates of 1.1 to 2 mm/year before 1990 [1] towards unprecedented high rates of 3.3 ± 0.4 mm/year afterwards [2] and is expected to continue its acceleration in a warming climate primarily as a result of melting ice and ocean thermal expansion [3,4] giving rise to significant socioeconomic and environmental consequences on the coastal zones [5]. Rising seas can, however, deviate immensely on regional scale relative to the global mean owing to several processes acting at different locations on a range of timescales [6][7][8].…”

Effective inundation of continental United States communities with 21st century sea level rise

“…The East and Gulf Coasts of the US experienced some of the world's fastest rates of sea level rise during the 20th century (National Oceanic and Atmospheric Administration 2013a; Dangendorf et al 2017). These rising seas have caused tidal floodingcoastal flooding that is driven in large part by routine tidal fluctuations rather than precipitation or storm surge-to become an increasingly frequent occurrence in US coastal communities.…”