The world's largest High Arctic lake responds rapidly to climate warming

Abstract

Using a whole-watershed approach and a combination of historical, contemporary, modeled and paleolimnological datasets, we show that the High Arctic's largest lake by volume (Lake Hazen) has succumbed to climate warming with only a ~1 °C relative increase in summer air temperatures. This warming deepened the soil active layer and triggered large mass losses from the watershed's glaciers, resulting in a ~10 times increase in delivery of glacial meltwaters, sediment, organic carbon and legacy contaminants to Lake Hazen, a >70% decrease in lake water residence time, and near certainty of summer ice-free conditions. Concomitantly, the community assemblage of diatom primary producers in the lake shifted dramatically with declining ice cover, from shoreline benthic to open-water planktonic species, and the physiological condition of the only fish species in the lake, Arctic Char, declined significantly. Collectively, these changes place Lake Hazen in a biogeochemical, limnological and ecological regime unprecedented within the past ~300 years.

Fig. 1

Location of the Lake Hazen watershed and changes in glacier surface temperatures. Changes in summer glacier surface temperatures (°C y⁻¹) were quantified for the months of June, July and August for the period 2000–2012. The white line delineates the boundaries of the Lake Hazen watershed, and the glaciers within it (northern Ellesmere Island, Nunavut, Canada). The catchment area to lake area ratio for Lake Hazen is 12.7. The black line delineates the boundary of Quttinirpaaq National Park, Canada’s most northerly national park

Fig. 2

Changes in air and soil temperatures in the Lake Hazen watershed. a Mean annual change in monthly soil temperature (°C y⁻¹) for the period 1994–2010. b Difference in mean monthly soil temperature (°C) between the periods of 2007–2010 and 1994–2006, indicating that soil temperatures have primarily increased since 2007. c Increase in the number of days mean daily soil temperature was above freezing during 2007–2010 compared with the 1994–2006 baseline, showing a recent thickening of the soil active layer. Depth 0 is shielded air temperature at 1 m above the soil surface

Fig. 3

Temporal trends in surface temperature, ice phenology and ice cover at Lake Hazen. a Monthly mean (±SE) lake surface temperatures (°C) measured at 30 sites on Lake Hazen. b Onset dates (day of year) of melt and freeze-up. c Mean daily ice-free area (% of total lake area) on Lake Hazen between May 5 and September 5. For illustrative purposes, linear trend lines are shown, though none are significant (p > 0.05)

Fig. 4

Changes in glacier mass balance, glacial runoff and Lake Hazen discharge. a Modeled net annual mass balance (bars) and cumulative mass balance (line) for glaciers in the Lake Hazen watershed for 1948–2012. All values are in Gt, but note that the annual and cumulative mass balances are plotted on different y-axis scales. b Modeled glacial runoff (annual and 5-year running mean, 1948–2012) compared with measured daily discharge from Lake Hazen at the outflow (Ruggles River) from 1996 to 2012

Fig. 5

Sediment record of diatom abundance, geochemical parameters, contaminants and sedimentation rates. Diatom, geochemical and contaminant analyses were completed on three separate sediment cores collected in close proximity in May 2013 from the deepest location in Lake Hazen. One of these cores was used for ²¹⁰Pb radiometric dating (also see Supplementary Fig. 7) and calculation of sedimentation rates. This same core was analyzed for organic matter geochemistry and multi-element concentrations. OC organic carbon, C carbon, N nitrogen, P phosphorus, THg total mercury, OCP organochlorine pesticides. See Supplementary Fig. 4 for sediment concentration profiles of N, P and contaminants. The horizontal lines demarcate when diatoms first appear in the paleolimnological record in significant numbers (bottom), when the relative abundance of planktonic diatom species first began to increase (middle) and then surpassed that of benthic species (top)

Fig. 6

Physiological condition of Arctic Char (Salvelinus alpinus) in Lake Hazen. Fulton’s condition factor was calculated for Arctic Char with a mass of 200 g or greater collected between 1981 and 2014. Small open circles are condition factors for individual Arctic Char, whereas larger blue circles are mean condition factors for a given year. A quadratic trend line was fitted to all the data (p < 0.001). Arctic Char image credit: Kativik Ilisarniliriniq