Abstract
The northern coast of Ellesmere Island in the Canadian High Arctic is undergoing amplified warming that parallels the rapid decline in Arctic Ocean sea ice extent, and many lakes in this region have already shown changes in response to warming. However, biogeochemical data from High Arctic freshwaters are limited, and mostly restricted to the short, ice-free period. We sampled four coastal lakes in Stuckberry Valley (82°54′N, 66°56′W) before the onset of spring melting in 2017, 2018 and 2019, to assess biogeochemical gradients in their water columns and characteristics of their surface sediments. Despite their proximity, there were large differences in limnological properties. The two shallower lakes closer to the ocean were oxygen deficient, whereas the two deeper, more distant lakes were more oxygenated. There were pronounced vertical gradients in major ions, metals, and nutrients that suggested large differences in the extent of anaerobic microbial processes among the lakes. Morphometry and dissolved oxygen were the overriding determinants of biogeochemical differences rather than position along this short ocean–inland gradient. The diversity of limnological conditions, and the sensitivity of these characteristics to changes in ice cover, underlines the need for further study of under-ice processes in extreme northern lakes.
Highlights
The High Arctic is undergoing amplified climate change and a rapid decline in sea ice extent, which threatens the integrity of ecosystems throughout the region (Serreze and Barry 2011; Woelders et al 2018)
The northern coast of Ellesmere Island is a fast-changing area at the interface of the Canadian Arctic Archipelago and the Arctic Ocean ice pack. This north polar coastal area contains a variety of aquatic ecosystem types, including fiords, meromictic lakes, epishelf lakes, and supraglacial meltwater ponds. These key landscape components are closely linked to ongoing alterations in the High Arctic cryosphere; shifts in their carbon and nutrient cycles, such as changes in nutrient delivery and in greenhouse gas emissions, have already been observed and are predicted to increase under future climate change scenarios (Parmentier et al 2017; Roberts et al 2017)
Contrary to our hypothesis based on inspection of the highest available resolution topographic maps, the four lakes did not follow a continuous gradient based on emergence time, but instead separated into two groups that differed in morphometry and oxygenation: shallow deoxygenated waters at the lower sites and deep oxygenated waters at the two connected upper sites
Summary
The High Arctic is undergoing amplified climate change and a rapid decline in sea ice extent, which threatens the integrity of ecosystems throughout the region (Serreze and Barry 2011; Woelders et al 2018). The northern coast of Ellesmere Island is a fast-changing area at the interface of the Canadian Arctic Archipelago and the Arctic Ocean ice pack This north polar coastal area contains a variety of aquatic ecosystem types, including fiords, meromictic lakes, epishelf lakes, and supraglacial meltwater ponds. A recent study from Ward Hunt Lake is one of few to capture the annual cycle of a High Arctic aquatic ecosystem (Bégin et al 2020) Many of these northernmost lakes had perennial ice cover, but are transitioning towards seasonal or intermittent multiannual ice (Van Hove et al 2006; Apollonio and Saros 2014; Paquette et al 2015)
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