Low‐frequency variations in global mean sea level: 1950–2000

Abstract

[1] Low-frequency variability in global mean sea level (GMSL) is studied for the period 1950 -2000 by interpolating sparse tide gauge data to a global grid using empirical orthogonal functions (EOFs) of sea level variability determined from TOPEX/Poseidon (T/P) altimeter data. Results are based on data with long-term trends removed. The fact that the results do not have secular trends is an artifact of the analysis and should not be interpreted as an indication that sea level is not rising. The EOF reconstruction technique is discussed, and the resulting GMSL time series is compared to GMSL time series from Geosat and T/P altimetry and proxy GMSL time series estimated from global sea surface temperature data. The error assessment suggests the accuracy of the GMSL time series reconstructed from the tide gauge data is 2 -4 mm RMS for a 1 year running mean smoothing and about 1 mm for a 5 year running mean smoothing. Several El Niño/La Niña events are evident in the GMSL, as well as significant low-frequency variability at a 10-12 year period. GMSL appears to have been generally lower than normal in the late 1960s, throughout the 1970s, and in the 1980s. GMSL appears to have been generally higher than normal in the late 1950s and early 1960s and in the early 1980s and has been rising throughout the 1990s, when T/P is observing. The implication of the low-frequency signals on the determination the secular rate of GMSL from satellite altimetry is discussed.

El Niño, La Niña, and the global sea level budget

“…In particular, it has long been reported that nonseasonal GMSL anomalies are significantly correlated with El Niño-Southern Oscillation (ENSO), such that the GMSL is anomalously positive during warm El Niño phases and anomalously negative during cool La Niña phases (Nerem et al, 1999(Nerem et al, , 2010Chambers et al, 2002;Ngo-Duc et al, 2005;Landerer et al, 2008;Merrifield et al, 2009;Llovel et al, 2010Llovel et al, , 2011Boening et al, 2012;Cazenave et al, 2012Cazenave et al, , 2014Meyssignac and Cazenave, 2012;Stammer et al, 2013;Fasullo et al, 2013;Haddad et al, 2013;Meyssignac et al, 2013;Calafat et al, 2014;Dieng et al, 2014Dieng et al, , 2015Pugh and Woodworth, 2014). Recent papers argue that ENSO-related GMSL changes are essentially of barystatic origin, related to changes in the hydrological cycle, and patterns of precipitation and evaporation (Llovel et al, 2011;Boening et al, 2012;Cazenave et al, 2012Cazenave et al, , 2014Fasullo et al, 2013).…”

Sea level trend and variability in the Singapore Strait

“…For the Singapore area, the earlier rate was similar, but the later trend is somewhat higher, centered at 5 mm yr −1 . The larger regional trend since 1993 in the tropical Pacific and Indian Oceans has been attributed to considerable interannual and decadal sea level variability associated, respectively, with the ENSO and the North Pacific Decadal Oscillation (Trenberth and Hurrell, 1994;Chambers et al, 2002;Church et al, 2004Church et al, , 2006and Becker et al, 2011).…”

Past terrestrial water storage (1980–2008) in the Amazon Basin reconstructed from GRACE and in situ river gauging data

“…The method is similar to that classically used to reconstruct past atmospheric or oceanic fields such as marine sea level pressure (Kaplan et al, 2000), sea surface temperature (Smith and Reynolds, 2003) and sea level (Chambers et al, 2002;Church et al, 2004;Llovel et al, 2009;Calafat and Gomis, 2009). The method developed in the present study combines spatial information on TWS from GRACE (over 2003-2008) with multi-decade-long (over 1980-2008) but sparse river level time series based on in situ gauges.…”