Hurricane Impact on Seepage Water in Larga Cave, Puerto Rico

Abstract

Hurricane-induced rainfall over Puerto Rico has characteristic δ18O values which are more negative than local rainfall events. Thus, hurricanes may be recorded in speleothems from Larga cave, Puerto Rico, as characteristic oxygen isotope excursions. Samples of 84 local rainfall events between 2012 and 2013 ranged from −6.2 to +0.3‰, whereas nine rainfall samples belonging to a rainband of hurricane Isaac (23–24 August 2012) ranged from −11.8 to −7.1‰. Cave monitoring covered the hurricane season of 2014 and investigated the impact of hurricane rainfall on drip water chemistry. δ18O values were measured in cumulative monthly rainwater samples above the cave. Inside the cave, δ18O values of instantaneous drip water samples were analyzed and drip rates were recorded at six drip sites. Most effective recharge appears to occur during the wet months (April–May and August–November). δ18O values of instantaneous drip water samples ranged from −3.5 to −2.4‰. In April 2014 and April 2015 some drip sites showed more negative δ18O values than the effective rainfall (−2.9‰), implying an influence of hurricane rainfall reaching the cave via stratified seepage flow months to years after the event. Speleothems from these drip sites in Larga cave have a high potential for paleotempestology studies.