Evidence for abundant rainfall in the northern Bahamas from 4100 to 3300 years ago
Abstract
Small island developing nations, like The Bahamas, are dependent on seasonal rainfall to recharge local aquifers, which are then used to support society and agriculture. However, prehistoric evidence for how climate extremes (drought vs. pluvial) have impacted aquifer conditions remains poorly understood. The hydrographic conditions within groundwater-fed Caribbean blue holes is linked to local hydroclimate, and blue hole stratigraphy can preserve long-term records of internal hydrographic change in response to external forcing. Here we present subfossil meiofauna (foraminifera, ostracodes) results from two blue holes in the northern Bahamas (western Abaco Island, located 3.5 km apart in an N-S transect). Holocene environmental change within the blue holes has largely been driven by concomitant vertical groundwater and relative sea-level rise. However, both blue holes document an abrupt loss of water column stratification, oxygenation of the benthos, and salinity decrease from 4100 to 3300 years ago. Based on data from both blue holes, this represents a minimum vertical extent of a paleo meteoric lens of 13 m in thickness. We interpret this synchronous change in the benthic habitat of these two blue holes (from anoxic marine to oxygenated brackish) as reflecting western expansion of the paleo meteoric lens on Abaco Island from increased aquifer recharge, potentially from increased regional rainfall. This presentation will discuss ongoing results from numerical simulations attempting to evaluate potential drivers of this groundwater change, and discuss hypotheses related to potential external forcing of increased rainfall in the northern Bahamas from 4100 to 3300 years ago.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP43B1605L
- Keywords:
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- 1620 Climate dynamics;
- GLOBAL CHANGE;
- 1627 Coupled models of the climate system;
- GLOBAL CHANGE;
- 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHY;
- 4910 Astronomical forcing;
- PALEOCEANOGRAPHY