For Water on the Arctic Tundra, Timing Is Everything
Tracking water through Arctic polygons using isotopes reveals temporal link to meteorology and biogeochemistry.
Each spring, the Arctic Coastal Plain transforms from a cold and dry, wind-packed snowscape to a green tundra wetland, where a distinctive honeycomb-like pattern of “polygons” covers large areas due to the formation of vertical ice wedges. Researchers are using the isotopic signatures of water in these polygons to track where the surface water is coming from and where it is going during this critical transition period. In addition, researchers are coupling the timing of these hydrological transitions with the import and export of critical nutrients to and from the landscape and with meteorological datasets.
Climate modeling efforts require an accurate representation of Arctic tundra hydrology. This work demonstrates the tight coupling of the landscape water balance with biogeochemical cycles and with the landscape energy balance, inferred from meteorological data. By linking critical details like the landscape water balance and biogeochemical cycles to meteorological parameters that are already widely measured and can readily be measured or estimated remotely, this work provides a simple mechanism for the improved representation of tundra landscapes in models, which can range from watershed to global scales.
Hydrologically significant periods and transitions were identified using changes in the isotopic composition of polygon surface water. By monitoring the changing ratios of oxygen and hydrogen isotopes in surface water, scientists were able to identify the timing of important hydrological transitions—indiscernible by other methods—and compare them to the timing of biogeochemical changes and landscape energy-balance changes. Researchers found that the timing of these isotopically determined hydrological transitions aligned with the characteristic progression of physical changes described by previous literature. Because the timing of these physical changes is readily observed, or deduced from routine meteorological data, this work provides a mechanism for appraising hydrology and biogeochemistry in high-latitude regions where hydrological and biogeochemical datasets are sparse. This study also revealed that different types of polygons hold water from different sources and identifies the likely sources and sinks of various dissolved ions, including important nutrients, to and from the Arctic landscape.
Stan D. Wullschleger
Oak Ridge National Laboratory
- The data that support the findings of this study are made openly available in the NGEE–Arctic data repository.
This work was supported by the Next-Generation Ecosystem Experiments (NGEE)–Arctic project. NGEE–Arctic is supported by the Terrestrial Ecosystem Science program of the Office of Biological and Environmental Research (BER), within the U.S. Department of Energy (DOE) Office of Science.
Conroy, N. A., B. D. Newman, J. M. Heikoop, et al. “Timing and duration of hydrological transitions in Arctic polygonal ground from stable isotopes.” Hydrological Processes 34(3), 749–64 (2019). [DOI:10.1002/hyp.13623].