Forest-tundra water balance signals traced by isotopic enrichment in lakes

Enrichment of oxygen-18 and deuterium in surface waters is shown to be a useful indicator of water balance variations in remote, permafrost regions of northern Canada where hydroclimate monitoring networks are limited. Necessarily, such indicators must be applied with care as isotopic signals in each lake trace water balance and atmospheric conditions integrated over different time-periods and spatial areas, as determined by lake water-residence time and catchment drainage area. Isotopic enrichment in large lakes is found to be relatively stable in time, and, as interpreted in the context of steady-state models, will yield information more representative of regional climatological-scale processes. In contrast, seasonal isotopic enrichment in shallow lakes, which occurs due to extreme seasonality of the northern climate and short water residence times, may be useful for estimating short-term ‘point’ evaporation rates.