Holocene glacial fluctuations in southern South America

SAGREDO, ESTEBAN; KAPLAN, MICHAEL; REYNHOUT, SCOTT; ARAENA, JUAN CARLOS; MATEO MARTINI; STRELIN, JORGE; SCHAEFER, JOERG

San Francisco

Congreso; American Geophysical Union Fall Meeting 2016; 2016

AGU

Understanding thetiming and magnitude of former glacier fluctuations is critical to decipherlong-term climatic trends and to unravel both natural cycles and human impacton the current glacial behavior. Despite more than seven decades of researchefforts, a unifying model of Holocene glacial fluctuations in Southern SouthAmerica remains elusive. Here, we present the state-of-the-art regarding thetiming of Holocene glacial fluctuation in southern Patagonia-Tierra del Fuego,with a focus on a new generation of high-resolution radiocarbon and Be surface exposuredating chronologies. Recently acquired evidence suggest that after recedingfrom advanced Late Glacial positions, Patagonian glaciers were for the mostpart close to, or even behind, present ice margins during the Early Holocene.On the other hand, emerging chronologies indicate that in some areas there wereextensive expansions (century scale?) that punctuated the warm interval.Subsequently, we have evidence of multiple millennial timescale glacialadvances starting in the middle Holocene. Several glacial maxima are defined bymoraines and other landforms from ~7000years ago to the 19th century, with a gap sometime between 4,500 and 2,500 yearsago. The last set of advances began around 800-600 years ago. Although glacialactivity is documented in Patagonia at the same time as the European Little IceAge, the extent of these glacial events are less prominent than those of the mid-Holocene.The causes that may explain these glacial fluctuations remain elusive. Finally,we discuss ongoing efforts to better define the timing and extent of Holoceneglaciations in southern South America, and to establish the basis to testcompeting hypothesis of regional Holocene climate variability.