Early Holocene ice on the Begguya plateau (Mt. Hunter, Alaska) revealed by ice core ¹⁴C age constraints

Abstract

Investigating North Pacific climate variability during warm intervals prior to the Common Era can improve our understanding of the behavior of ocean–atmosphere teleconnections between low latitudes and the Arctic under future warming scenarios. However, most of the existing ice core records from the Alaskan and Yukon region only allow access to climate information covering the last few centuries. Here we present a surface-to-bedrock age scale for a 210 m long ice core recovered in 2013 from the summit plateau of Begguya (Mt. Hunter; Denali National Park, Central Alaska). Combining dating by annual layer counting with absolute dates from micro-radiocarbon dating, a continuous chronology for the entire ice core archive was established using an ice flow model. Calibrated 14C ages from the deepest section (209.1 m, 7.7 to 9.0 ka cal BP) indicate that basal ice on Begguya is at least of early Holocene origin. A series of samples from a shallower depth interval (199.8 to 206.6 m) were dated with near-uniform 14C ages (3 to 5 ka cal BP). Our results suggest this may be related to an increase in annual net snow accumulation rates over this period following the Northern Hemisphere Holocene Climate Optimum (around 8 to 5 kyr BP). With absolute dates constraining the timescale for the last >8 kyr BP, this paleo-archive will allow future investigations of Holocene climate and the regional evolution of spatial and temporal changes in atmospheric circulation and hydroclimate in the North Pacific.