Developing a Paleo-proxy of Submarine Groundwater Discharge


OCCI Funded Project: 2009


Submarine groundwater discharge is the flow of water from land to the sea, but unlike rivers, this flow occurs underground. This component of the hydrologic cycle is proving to be volumetrically as important as river flow with respect to chemical fluxes to the coastal zone. In many coastal areas, groundwater is the dominant source of nutrients, trace metals and pollutants.

Given that marine sciences interest in submarine groundwater discharge is quite new, there exists only a very limited understanding of the temporal variability of this process on decadal time scales. The temporal dynamics of this process are necessary to understand how groundwater discharge will respond to climate change, and thus how coastal systems sensitive to groundwater discharge will react to climate shifts such as changing rainfall patterns. What is required to fill this knowledge gap is a high-resolution historical record of submarine groundwater discharge. 

This proposal, Developing a Paleo-Proxy of Submarine Groundwater Discharge, outlines the concept behind a novel set of paleo-proxies for quantifying this important component of the hydrologic cycle.  We seek to utilize coral records from the tropical Pacific (Guam) to evaluate the temporal variability in groundwater discharge on seasonal, yearly and decadal time-scales. Here, corals are uniquely positioned to record changes in coastal ocean chemistry at the interface between land and sea, and thus are ideally situated to record a temporal SGD signal. The tropical Pacific region actively responds to El Niño/La Niña climate shifts and experiences periodic cyclones that impact groundwater stores via extreme precipitation events. While coral paleo-proxies for sea surface temperature are widely used, a groundwater discharge proxy will rely on separating the temperature signal from the groundwater chemical signal and the development of new analytical techniques for some of the elements of interest. With these uncertainties and lack of any preliminary data, this work is unlikely to be funded at present by traditional means. We hope to develop further evidence for the utility of this paleo-proxy by creating a credible historical record with which to pursue further funding.