Abstract
To better understand global mean sea level (GMSL) as an indicator of climate variability and change, contributions to its interannual variation are quantified in the Community Earth System Model (CESM) Large Ensemble and Last Millennium Ensemble. Consistent with expectations, the El Niño/Southern Oscillation (ENSO) is found to exert a strong influence due to variability in rainfall over land (PL) and terrestrial water storage (TWS). Other important contributors include changes in ocean heat content (OHC) and precipitable water (PW). The temporal evolution of individual contributing terms is documented. The magnitude of peak GMSL anomalies associated with ENSO generally are of the order of 0.5 mm·K−1 with significant inter-event variability, with a standard deviation (σ) that is about half as large The results underscore the exceptional rarity of the 2010/2011 La Niña-related GMSL drop and estimate the frequency of such an event to be about only once in every 75 years. In addition to ENSO, major volcanic eruptions are found to be a key driver of interannual variability. Associated GMSL variability contrasts with that of ENSO as TWS and PW anomalies initially offset the drop due to OHC reductions but short-lived relative to them. Responses up to 25 mm are estimated for the largest eruptions of the Last Millennium.
Highlights
Global mean sea level (GMSL) is a key indicator of the Earth’s energy and water cycles
The contributions to interannual variability in GMSL have been quantified using the multi-member ensembles provided by the Community Earth System Model (CESM) Large and Last Millennium Ensemble projects
The analysis provides a means for quantifying and understanding variability to a degree that is not currently possible using observations, yet is critical for interpreting associated variability and related issues such as sea level rise acceleration [26,45] in modern data records
Summary
Global mean sea level (GMSL) is a key indicator of the Earth’s energy and water cycles It has been precisely and accurately estimated from satellite altimetry for over two decades and reconstructions from tide gauges extend into the early 19th century [1,2], with individual gauge records extending back to the early 18th century. A detailed understanding of variability in global mean sea level has been made possible by advances in observing systems These include the ARGO array of in-situ ocean observing sensors, providing ocean temperature data of unprecedented sampling density, accuracy, and stability [7], and the GRACE satellites, which provide surface mass variability estimates [8].
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