Journal Article

Significant Local Sea Level Variations Caused by Continental Hydrology Signals

Purcell, Anthony, McQueen, Herb, McGirr, Rebecca, Tregoning, Paul

2024

Overview

Space gravity missions have enabled the quantification of the mass component of sea‐level rise over the past two decades. Barystatic sea‐level rise is predominantly driven by melting polar ice sheets and mountain glaciers. However, continental hydrological processes also contribute to global sea level change at significant magnitudes. We show that for most coastal areas in low‐to‐mid latitudes, up to half of manometric sea‐level rise is due to changes in water storage in ice‐free continental regions. At other locations the direct attraction effect of anthropogenic pumping of groundwater over the duration of the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow‐On (GRACE‐FO) mission offsets sea‐level rise from ice sheet and glacier melt. If these trends in continental hydrological storage were to slow or stop, these regions would experience greatly accelerated sea‐level rise, posing a risk to coastal settlements and infrastructure, however, for most coastal communities current rates of sea‐level rise would be significantly reduced. Plain Language Summary It is well understood that melting of polar ice sheets and mountain glaciers cause increases in ocean mass, leading to a corresponding rise in global sea level. What is not as obvious is that multi‐year changes in the storage of water on continents not covered by ice also contribute significantly to changes in global sea level. Over recent years and in some locations, the magnitude of these “continental hydrology” contributions to sea level changes have been comparable to the contributions of the ice‐covered regions. In some cases, the former have offset the ice sheet contributions, thus reducing regional sea‐level rise to substantially smaller magnitudes. Through an analysis of space gravity data, we have quantified the effects of continental hydrology on regional sea level and show that changes caused both naturally (e.g., through La Niña events) and through anthropogenic activities (e.g., extraction of groundwater) can increase or decrease regional sea level by significant amounts. Key Points Exchange of water between continents and oceans causes global sea level change at rates comparable to the contributions of ice sheets The direct gravitational attraction effect on local sea level is of a larger magnitude than the far‐field sea level changes Inter‐annual continental hydrology signal impacts on local sea level have negated the impacts of melting polar ice sheets in some locations

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Anthropogenic factors / Coastal zone / Continental hydrology / El Nino phenomena / Glaciation / Glacier melting / Glaciers / Global sea level / GRACE (experiment) / Gravity data / Groundwater / Hydrologic processes / Hydrology / Ice / Ice cover / Ice sheets / La Nina / La Nina events / Melting / Mountain glaciers / Mountains / Regions / Sea level / Sea level changes / Sea level rise / Sea level variations / Space missions / Water storage