SPELEOTHEM EVIDENCE OF HIGH-LATITUDE TELECONNECTION TO NORTHERN GULF OF MEXICO CLIMATE DYNAMICS DURING THE LAST 3,200 YEARS

Speleothems render important, precisely-dated terrestrial paleoclimate archives to compliment reconstructions from a growing number of ice and sediment cores. However, in contrast to the enormous quantity of limestone caves, there is a paucity of speleothem data from the southeastern United States. Here we present a 3.2 kyr speleothem paleorainfall record retrieved from continuously-monitored Hollow Ridge Cave (HRC), Marianna, FL, USA [1, 2].

Speleothem HRC2 was sampled at 0.5 mm intervals for isotopes (δ¹³C and δ¹⁸O) and trace elements (Mg, Sr, Ba, U), with an age model constructed from 29 ¹⁴C dates that was tuned to several absolute (U/Th) dated speleothems from the Gulf of Mexico region [3, 4]. HRC2 displays three major (~4‰) excursions in δ¹³C which we interpret as changes in ventilation and drip CO₂ degasing. HRC2 δ¹⁸O demonstrates decadal to centennial oscillations in rainfall intensity on the order of ~1‰ that are nearly synchronous with the GISP2 temperature record [5]. In-situ calibrations suggest that typical decadal variations in δ¹⁸O represent rainfall amount variations between 100-200 mm/yr or more. A pronounced -1.7‰ shift in δ¹⁸O between 1575-1315 yBP marks an episode of extreme rainfall intensity (+400-500 mm/yr), in phase with a signficant polar warming trend that roughly coincides with the termination of the Dark Age Cold Period (DACP).

This atmospheric teleconnection will be explored in an effort to increase our understanding of how centennial high-latitude warming and cooling can affect northern Gulf of Mexico rainfall patterns and therefore groundwater recharge to the Floridan aquifer.

[1] Tremaine et al. (2011) GCA 75, 4929-4950; [2] Tremaine and Froelich (2013) GCA 121, 522-545; [3] Lachniet et al. (2012) Geology 40, 259-262; [4] Medina-Elizalde et al. (2013) EPSL 298, 255-262; [5] Kobashi et al. (2011) GRL 38, L21501.