Late Holocene climatic variability in Subarctic Canada: Insights from a high-resolution lake record from the central Northwest Territories.

April S Dalton,Andrew L Macumber,Hendrik Falck,Helen M Roe,Jennifer M Galloway,Graeme T Swindles,R Timothy Patterson,Jesse C Vermaire,Carley A Crann

doi:10.1371/journal.pone.0199872

Abstract

We examined late Holocene (ca. 3300 yr BP to present-day) climate variability in the central Northwest Territories (Canadian Subarctic) using a diatom and sedimentological record from Danny’s Lake (63.48ºN, 112.54ºW), located 40 km southwest of the modern-day treeline. High-resolution sampling paired with a robust age model (25 radiocarbon dates) allowed for the examination of both lake hydroecological conditions (30-year intervals; diatoms) and sedimentological changes in the watershed (12-year intervals; grain size records) over the late Holocene. Time series analysis of key lake ecological indicators (diatom species Aulacoseira alpigena, Pseudostaurosira brevistriata and Achnanthidium minutissimum) and sedimentological parameters, reflective of catchment processes (coarse silt fraction), suggests significant intermittent variations in turbidity, pH and light penetration within the lake basin. In the diatom record, we observed discontinuous periodicities in the range of ca. 69, 88–100, 115–132, 141–188, 562, 750 and 900 years (>90% and >95% confidence intervals), whereas the coarse silt fraction was characterized by periodicities in the >901 and <61-year range (>95% confidence interval). Periodicities in the proxy data from the Danny’s Lake sediment core align with changes in total solar irradiance over the past ca. 3300 yr BP and we hypothesize a link to the Suess Cycle, Gleissberg Cycle and Pacific Decadal Oscillation via occasional inland propagation of shifting air masses over the Pacific Ocean. This research represents an important baseline study of the underlying causes of climate variability in the Canadian Subarctic and provides details on the long-term climate variability that has persisted in this region through the past three thousand years.

Highlights

General Circulation Models predict that near-future climate warming in Arctic and Subarctic regions will be of a greater magnitude than projected for lower latitudes [1]
D. stelligera complex declines slightly in abundance at ca. 1000 cal years before present (yr BP), which may be a response to warming associated with the Medieval Climate Anomaly (MCA), which has been inferred in other studies from the region [4] as well as throughout Arctic Canada between ca. 1100 to ca. 900 yr BP [73]
Our results suggest that Pacific Ocean climate variability influenced climate in the Canadian Subarctic intermittently over the past ca. 3300 cal yr BP

Summary

Introduction

General Circulation Models predict that near-future climate warming in Arctic and Subarctic regions will be of a greater magnitude than projected for lower latitudes [1]. To improve the predictive power of these models, and to put climate warming projections into the context of natural variability in the northern climate system, it is important to obtain empirically derived paleoclimate reconstructions from the region. Despite numerous studies on these widespread lacustrine records, our understanding of the long- and short-term climate dynamics that have influenced the Arctic and Subarctic regions remains incomplete [5,6,7]. There is a need for additional regionally representative climate studies to understand more thoroughly long-term variability

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Discussion

Conclusion