Estimating the regional climate signal in a late Pleistocene and early Holocene lake-sediment δ¹⁸O record from Vermont, USA.

Abstract

We present a new oxygen isotope (δ18O) record from carbonate-rich lake sediments from central Vermont. The record from Twin Ponds spans from 13.5 cal ka BP (1950 AD) to present, but contains a 6 ka long hiatus starting shortly after 7.5 cal ka BP. We compare the record for ca. 13.5–7.5 cal ka BP with published δ18O data from the region after using a Bayesian approach to produce many possible chronologies for each site. Principal component analysis then identified chronologically-robust, multi-site oxygen isotope signals, including negative values during the Younger Dryas, but no significant deviations from the early Holocene mean of the regional records. However, differences among sites indicate significant trends that likely relate to interacting changes in the regional gradients of seasonal temperatures and precipitation as well as moisture sources, moisture pathways, and aridity that were controlled by large-scale climatic controls such as insolation, the progressive decline of the Laurentide Ice Sheet, and changes in oceanic circulation. Centennial shifts punctuate these trends at ca. 9.3 and 8.2 cal ka BP, and reveal that the local character of these short-lived features requires a detailed understanding of lake hydrology and regional isotopic gradients to yield reliable information for regional climate reconstructions.

Midcontinental Native American population dynamics and late Holocene hydroclimate extremes

“…These smaller, constrained populations may have persevered due to 1) local climatic conditions, 2) a reduced population size that could be supported by floodplain agriculture alone, or 3) local socio-political autonomy that was more resilient and responsive to drought-induced resource stress. In the southeastern and eastern US (e.g., New York, the Ontario Peninsula, and regions along the east coast and lower drainages of the Delaware and Susquehanna Rivers), the persistence and even thriving, of Native American populations during and following the midcontinental abandonment 20 is consistent with a decreasing PNA influence on climate with increasing distance from the Ohio River Valley 32 , as illustrated by the attenuated variability in paleoclimate records spanning the last millennium as compared with the Martin Lake results 48 49 50 .…”

Detecting past changes in vegetation resilience in the context of a changing climate

“…We examine fossil pollen datasets from Rogers Lake, Connecticut, USA [19] and Summit Lake, Colorado, USA [18]. Lake sediment oxygen isotopes from each region provide constraints on the climate changes [20,21].…”

A multi-proxy reconstruction of climate during the late-Pleistocene to early Holocene transition in the northeastern, USA

“…The preparation and measurement of <63 μm bulk carbonate for stable isotope analysis is described fully by Mandl et al (2016). This fraction of CaCO 3 is primarily composed of inorganically precipitated CaCO 3 and reflects the isotopic composition of water at the depth and time of formation.…”

“…The chronology for the entire 255 cm core was developed by Mandl et al (2016) using 9 14 C ages measured with accelerated mass spectrometry (AMS) at the Keck Carbon Cycle AMS Laboratory at the University of California, Irvine. The late-glacial portion of the record is from ca.…”