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

Abstract

Abstract. Previous studies show that nonseasonal variations in global-mean sea level (GMSL) are significantly correlated with El Niño-Southern Oscillation (ENSO). However, it has remained unclear to what extent these ENSO-related GMSL fluctuations correspond to steric (i.e., density) or barystatic (mass) effects. Here we diagnose the GMSL budget for ENSO events observationally using data from profiling floats, satellite gravimetry, and radar altimetry during 2005–2015. Steric and barystatic effects make comparable contributions to the GMSL budget during ENSO, in contrast to previous interpretations based largely on hydrological models, which emphasize the barystatic component. The steric contributions reflect changes in global ocean heat content, centered on the Pacific. Distributions of ocean heat storage in the Pacific arise from a mix of diabatic and adiabatic effects. Results have implications for understanding the surface warming slowdown and demonstrate the usefulness of the Global Ocean Observing System for constraining Earth's hydrological cycle and radiation imbalance.

Sea-level change in the Dutch Wadden Sea

“…Several studies computed trends over the Argo period. The trends appeared to be unchanged with respect to the 1993-2010 period, with estimates of 0.8 ± 0.2 mm a −1 over 2004-2015.5 (Llovel et al, 2014), 1.0 ± 0.5 mm a −1 over 2005-2013(Leuliette, 2015, and 1.0 ± 0.2 mm a −1 over 2005-2016 (Piecuch & Quinn, 2016). Piecuch & Quinn (2016) also demonstrated that approximately half of the GMSL variability is explained by the steric water level variations.…”

On the “Cal‐Mode” Correction to TOPEX Satellite Altimetry and Its Effect on the Global Mean Sea Level Time Series

“…The sea level rate over the past few years has markedly increased to over 6 mm/yr. We should probably stress the obvious point that a fitted polynomial is not a physical model, so it reveals nothing about rates after 2016, nor does it shed light on causative mechanisms, which for the more recent few years may well be related to unusually strong La Niña and El Niño events (Fasullo et al, ; Piecuch & Quinn, ). The recent high sea level rates do correspond to an increasing rate of mass influx into the ocean, as revealed by GRACE gravity measurements—see, for example, Figure 2 of Leuliette ()—as well as an increasing rate of thermal expansion (Cheng et al, ).…”

The Dominant Global Modes of Recent Internal Sea Level Variability

“…In the context of understanding and preparing for future sea level change, internal climate variability plays two primary roles: (1) it serves to obscure the background anthropogenic trend in sea level, particularly in short data records, and (2) it causes an increase or decrease in regional and global sea level on short timescales that can temporarily ameliorate or exacerbate the effects of long‐term sea level rise. In recent years, many studies have investigated these two roles, seeking to separate and quantify the sea level variability associated with a variety of large‐scale modes of climate variability (e.g., Bromirski et al, ; Cazenave et al, ; Hamlington et al, , , ; Han et al, ; Moon et al, , ; Palanisamy et al, ; Piecuch & Quinn, ; Sreenivas et al, ; Zhang & Church, ). In doing so, there is the potential to both uncover the long‐term trend that may be expected to persist into the future and provide an assessment of the envelope of possible sea level change on shorter planning horizons.…”

“…In doing so, there is the potential to both uncover the long‐term trend that may be expected to persist into the future and provide an assessment of the envelope of possible sea level change on shorter planning horizons. An approach in these studies is to perform statistical analysis focusing on a particular timescale of interest, comparing the results to indices used to track large‐scale climate modes or even using these indices as part of the analysis (e.g., Bromirski et al, ; Piecuch & Quinn, ; Zhang & Church, ; broadly summarized in Han et al, ). Particular focus has been placed on intraseasonal to decadal timescales, over which regional mean sea level is dominated by basin‐scale ocean‐atmosphere modes of internal climate variability.…”

“…As a result, the focus here is on modern observational records, including those with relatively short record lengths and with trends that are potentially heavily impacted by variability on intraseasonal to decadal timescales. In doing so, insight can be gained on the role the water cycle plays in sea level variability (Cazenave et al, ; Hamlington et al, ; Reager et al, ), the extent to which terrestrial water storage (TWS) varies in response to large‐scale climate variability (e.g., Boening et al, ; Fasullo et al, ), and the relative roles of steric and mass‐driven variability to changes in regional and global sea level (Cazenave et al, ; Piecuch & Quinn, ). While not specifically relying on comparisons to climate indices, the general approach taken here does not preclude links or attribution to well‐known climate signals like ENSO or the PDO.…”