Climate and permafrost effects on the chemistry and ecosystems of High Arctic Lakes

Abstract

Permafrost exerts an important control over hydrological processes in Arctic landscapes and lakes. Recent warming and summer precipitation has the potential to alter water availability and quality in this environment through thermal perturbation of near surface permafrost and increased mobility of previously frozen solutes to Arctic freshwaters. We present a unique thirteen-year record (2003-16) of the physiochemical properties of two High Arctic lakes and show that the concentration of major ions, especially SO₄^2-, has rapidly increased up to 500% since 2008. This hydrochemical change has occurred synchronously in both lakes and ionic ratio changes in the lakes indicate that the source for the SO₄^2- is compositionally similar to terrestrial sources arising from permafrost thaw. Record summer temperatures during this period (2003-16) following over 100 years of warming and summer precipitation in this polar desert environment provide likely mechanisms for this rapid chemical change. An abrupt limnological change is also reflected in the otolith chemistry and improved relative condition of resident Arctic char (Salvelinus alpinus) and increased diatom diversity point to a positive ecosystem response during the same period.

Figure 1

(A) Regional Map of Cape Bounty, Melville Island, NU and Mould Bay, Prince Patrick Island, NT. (B) Regional summer (June, July, August) temperatures since 1948 (Mould Bay), and (C) summer air temperatures and precipitation at CBAWO 2003–15 (WestMet). Map prepared with data from http://www.nrcan.gc.ca/earth-sciences/geography/atlas-canada using ArcGIS v.10.4, and contains information licensed under the Open Government Licence – Canada.

Figure 2

(A) Concentrations of SO₄ ²⁻ (mg/L) and Mg²⁺/Ca²⁺ ratios (mg/L) over time for (A) West and (B) East. SO₄ ²⁻/Na⁺ and SO₄ ²⁻/Cl⁻ ratios of (C) West and (D) East Lakes compared to marine water, regional hypersaline lakes and West catchment streams (disturbed = Ptarmigan, Undisturbed = Goose, 2007–09, Lamoureux and Lafrenière (2013), 2012 Unpublished Data). Dashed line indicates a 1:1 ratio.

Figure 3

Elemental maps (A) Ba and (B) Mg of East Lake otolith sampled in 2015. (C,D) Principal component analysis of inner/outer otolith data 2013–2015: 10 fish from West, 10 fish from East, and 2 fish from Headwater. Circle = Inner Otolith, X = Outer Otolith.

Figure 4

(A) Relative Fish Condition for East and West Lake 2008–15. Note: sample data are not available from 2010. (B) Percent planktonic shifts (Cyclotella pseudostelligera and Cyclotella rossii, grouped as Cyclotella s.l.) 2004 and 2014.