| Autor: |
Ganju, Neil K., Pohlman, John W., Suttles, Steven E., Brankovits, David |
| Předmět: |
|
| Zdroj: |
Geophysical Research Letters; Nov2024, Vol. 51 Issue 22, p1-10, 10p |
| Abstrakt: |
Karst subterranean estuaries within globally ubiquitous carbonate aquifers are coastal groundwater ecosystems that provide an essential water resource for human populations. To understand the drivers of salinization within a coastal aquifer in the Yucatan Peninsula (Mexico), we employed hydroacoustics in flooded caves to observe how oceanic and atmospheric events facilitate mixing between the meteoric lens (fresh‐brackish groundwater) and the saline groundwater on tidal and episodic timescales. Precipitation during Tropical Storm Carlotta increased the flow and salinity of the meteoric lens without evidence for vertical mixing across the halocline. We postulate that vertical migration of haloclines in the conduit relative to those within the rock matrix during precipitation creates lateral density gradients that drive mixing, and ultimately creates a brackish layer within the meteoric lens. These results provide a mechanistic explanation for vertical and lateral exchange in a coastal carbonate aquifer, which has implications for groundwater response to future climatic change. Plain Language Summary: Karst subterranean estuaries are regions of coastal aquifers where fresh and marine water mix within porous limestone bedrock that often contains extensive cave networks. These coastal aquifers are globally distributed and are a critical water resource increasingly stressed by sea‐level rise, climate change, and human activity. We installed acoustic devices and other sensors in the most extensively mapped underwater coastal cave on Earth to image and understand how rainfall‐derived fresh water and saltwater mix underground. We found that salinization of the low‐salinity portion of the aquifer following intense rainfall‐led mixing can temporarily render the water unsafe for drinking and useless for irrigation. We developed a conceptual model that describes how tides and rainfall‐driven changes cause saline water to drain laterally from the porous limestone bedrock and mix with fresher waters in open cave passages rather than by vertical mixing between water layers, as previous studies have suggested. Key Points: We present novel hydroacoustic observations of halocline dynamics within a karst subterranean estuary during Tropical Storm CarlottaIncreased precipitation resulted in increased salinity of the brackish layer of the aquifer despite stability of haloclinesDifferential vertical halocline movement in caves and the adjacent rock matrix drives lateral mixing between brackish and saline groundwater [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
Plný text