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 SO42−, 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 SO42− 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.
Highlights
The aquatic ecosystems of High Arctic freshwater lakes are strongly influenced by the presence of persistent ice cover and permafrost
This study documents recent rapid chemical change in two similar adjacent High Arctic lakes (Fig. 1) using a long-term data set from the Cape Bounty Arctic Watershed Observatory (CBAWO), a limnological and hydrological research site in the Canadian Arctic Archipelago (74°50’N, 109°30’W)
The most substantial physical change recorded by the lakes is an abrupt rise in turbidity in West Lake from ~4 Nephelometric Turbidity Units (NTU) in 2006, to over 250 NTU in 2015 (Supplementary Fig. S1), while the East Lake turbidity has consistently remained
Summary
Many studies indicate that Arctic regions are undergoing rapid climatic and permafrost change[2,3,4,5,6] Small aquatic systems such as ponds have demonstrated abrupt physiochemical and ecosystem responses[7], while larger lakes are thought to be more likely to gradually respond due to their larger volume[8]. Recent studies have documented near surface permafrost degradation leading to altered shallow hydrological pathways[6], increased groundwater contribution and solute and nutrient delivery to Arctic river basins[15,16], but the impact has not been demonstrated in relatively large lake systems mostly due to their greater volume and slow water turnover. Lake diatom communities were enumerated in 200421 and 2014 to determine changes in species composition during this period of rapid change
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