Three ice cores drilled to bedrock atop Nevado Coropuna, southwestern Peru reflect Holocene and late glacial stage climate variability. Two cores measure <34 m in length yet provide seemingly continuous >16 kyr histories, and thus represent the shortest known ice cores to extend from the present into the last glacial. High major ion concentrations and dust particle diameter ratios identify a succession of abrupt and severe Holocene droughts on the Altiplano centered at 3.4, 4.2, 5.6, 7.5, 8.2 and 10.1 kyr B.P. Modern precipitation availability in the region is dominated by ENSO variability on interannual timescales and these events may thus reflect extended periods of El Niño-like conditions in the tropical Pacific. The Deglaciation Climate Reversal, the tropical counterpart to the Northern Hemisphere Younger Dryas stadial, is marked by large, abrupt stable isotopic depletion, with δ18O ~9-10 per mil lower at this time relative to the early Holocene. This δ18O shift is remarkable as it is ~4-5 per mil greater than that observed in any previously drilled central Andean ice core record. In concert with marked, synchronous deuterium-excess increases, these shifts may be explained by a coeval southward migration of the ITCZ. Decreased major ion and dust concentrations and low dust particle diameter ratios likely reflect increased central Andean precipitation at this time, in agreement with other regional paleoclimate records.
A complete history could not be produced for the third core due to conflicting dating results. Annual resolution over the past 244 years allows for a detailed assessment of recent regional climate change and its relation to possible forcings. Decadal δ18O variability is strongly correlated with tropical Pacific sea surface temperatures and lends support to precipitation, via the amount effect, controlling δ18O on these timescales. On longer timescales, temperature plays an increasingly important role in governing this parameter and it is suggested that 20th century δ18O enrichment is influenced by recent tropospheric warming resulting from anthropogenic greenhouse gas emissions.
Radiocarbon dating of well preserved, in-place vegetation exposed by the retreating Quelccaya Ice Cap, southeastern Peru constrains the last time the ice cap's extent was smaller than at present. Seventeen plant samples from two sites along the central western margin collectively date to 4.7 and 5.1 kyr B.P. and strongly indicate that current ice cap retreat is unprecedented over the past ~5 millennia. Seventeen vegetation samples interbedded in a nearby clastic sedimentary sequence suggest ice-free conditions at this site from ~5.2 to at least ~7 kyr B.P., and place minimum constraint on early- to mid-Holocene ice cap extent.
A growing body of globally distributed, independently dated paleoclimate records collectively identifies a series of contemporaneous abrupt climate change events during the Holocene that are generally coeval with reductions in solar output. A mechanistic hypothesis for these events, involving the tropical Pacific shifting to an El Niño-like mean state via a non-linear response of the coupled ocean-atmosphere system to reduced radiative heating, is discussed. Support for this explanation utilizing the abrupt drought events captured in the CRC1 record is equivocal.