Landscape Controls on Thermokarst Lake Water Fluxes between Inuvik and Tuktoyaktuk, Northwest Territories, Canada.
Abstract
The Arctic is warming at twice the rate of the rest of the world, causing precipitation to shift from snowfall to rainfall, longer snow-free and ice-free summers, increased evapotranspiration, and permafrost thaw. It is necessary to understand how thermokarst lake water fluxes will react to these changes if we are to predict future greenhouse gas fluxes from lakes. Greenhouse gas fluxes from lakes are tied to the amount of lateral carbon delivery into the lake, the residence time of lake waters, and the temperature of lake waters, all of which are regulated by lake water fluxes and lake characteristics.
We measured lake water flux components at multiple spatial and temporal scales across the 5000 km2 boreal - tundra transition zone between Inuvik and Tuktoyaktuk, Northwest Territories, Canada. Lake water flux components were measured at two adjacent thermokarst lakes with different ratios of lake area to catchment area (LACA), from 2017 - 2019. Also, stable water isotope samples were collected from March - September 2018 from ~100 lakes across 2000 km2. From these samples we estimated the ratio of evaporation to inflow, residence time, and the mixture of snowmelt and rainfall runoff in each lake. Catchments of all 7500 lakes in the region were delineated using a high-resolution digital elevation model in order to estimate their LACA, and evaluate connectivity between lakes. Lake temperature, conductivity, dissolved oxygen, pH, DOC, DON, and chlorophyll profiles were also measured from ~50 lakes pre-snowmelt in 2019. Lakes with a smaller LACA had a larger portion of their inflow evaporate, longer residence times, and have less of their water replaced after rainfall events. Coupling isotope samples taken before, during, and after snowmelt with field observations also revealed that the majority of snowmelt runoff flowed overtop of lake ice and through the outlet, as the lake ice stopped snowmelt runoff entering the lake until it had melted sufficiently. LACA and lake connectivity also varied greatly across the 7500 lakes in the region. Further work this year will compare lake limnological properties and greenhouse gas fluxes with LACA and other lake and catchment properties.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C24B..01W
- Keywords:
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- 0702 Permafrost;
- CRYOSPHERE;
- 0708 Thermokarst;
- CRYOSPHERE;
- 0768 Thermal regime;
- CRYOSPHERE;
- 0774 Dynamics;
- CRYOSPHERE