117-10 An annually resolved lake sediment carbonate δ18O record from lowland Guatemala reflects Circum-Caribbean atmospheric circulation over the past 220 years

Abstract:

Establishing robust proxy-precipitation relationships is necessary to improve paleoclimate interpretations for Central America, where a scarcity of local-scale and high-resolution paleo-records limits the resolution of current climate models. To address this need, we developed an annually resolved record of oxygen isotope ratios (¹⁸O:¹⁶O; δ¹⁸O) preserved in the sedimentary archive of Lake Lachuá, Guatemala, spanning the past 220 years and compared it with meteorological reanalysis data spanning the past 100 years. This comparison showed that the Lachuá δ¹⁸O record was in-phase with annual precipitation totals (i.e., increased precipitation corresponded with higher δ¹⁸O values and vice versa), opposite to the expected relationship described by the “amount effect”. We propose that the Lachuá sediment δ¹⁸O reflects changes in moisture transport pathways, driven by expansions and contractions of the North Atlantic Subtropical High (NASH). During NASH expansions, the Caribbean Low-Level Jet (CLLJ) becomes southerly-displaced and more meridional. This lengthens the distance that vapor masses travel before reaching Lachuá, increasing downstream rainout and resulting in reduced precipitation and lower δ¹⁸O values in precipitation delivered to the site. Under a contracted NASH, the opposite occurs: The CLLJ flows zonally and directly to Lachuá, resulting in increased precipitation and higher precipitation δ¹⁸O. Our data demonstrate that δ¹⁸O preserved in the Lachuá sediments can be used to track variability in Circum-Caribbean atmospheric circulation through time and provides a framework for deeper-time proxy-climate interpretations at the site.

Geological Society of America Abstracts with Programs. Vol. 58, No. 5, 2026

doi: 10.1130/abs/2026AM-21776

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