April 14, 2017
A synthesis of thermokarst lake water balance in high-latitude regions of North America from isotope tracers
By Lauren MacDonald, Brent Wolfe, Kevin Turner, Lesleigh Anderson (GECSC), and others. Published in Arctic Science.
Thermokarst lakes are unique Polar features and are undergoing varied hydrological transitions in response to recent climate changes. This study found substantial diversity of thermokarst lake change across Alaska and Canada by synthesizing 376 surface water isotope compositions for the past decade. These results characterized the varying influence of snowmelt, rainfall, permafrost thaw, and evaporation. The study assessed the controls on thermokarst lake water balance and how these vary among the studied regions and with differing environmental drivers. While some regional patterns emerged, overall, the results highlight the complexity of predicting hydrological responses to future climate change.
April 11, 2017
Long-term flow-through column experiments and their relevance to natural granitoid weathering rates
By Art White, Marjorie Schulz, Corey Lawrence (GECSC), Davison Vivit, and David Stonestrom. Published in Geochimica et Cosmochimica Acta.
Natural granitoid weathering is complex and inherently heterogeneous, with large differences observed in field versus laboratory estimates of weathering rates. To shed light on this problem and other uncertainties in weathering processes, pairs of fresh and partly-weathered granitoids, obtained from four well-characterized watersheds, were reacted in columns under ambient laboratory conditions for 13.8 years, the longest running experimental weathering study to date. Weathering rates observed in this long term column studies were an order of magnitude slower than those obtained from short term laboratory measurements but still 2 to 3 orders of magnitude faster than natural rates estimated from field data. Reactive transport modeling of the column system indicated that much slower experimental flow rates are required in order for transport limitation of weathering to drive rates down to levels observed in the natural system. Extending this modeling to the natural weathering system showed that still greater reductions in fluid flow rates along with the intrinsic plagioclase dissolution and kaolinite precipitation rates were needed to match observations of long term weathering. One explanation for these results is that exposure to reactive mineral surfaces is significantly limited in the natural environment compared to column experiments.
March 30, 2017
Integrating Radarsat-2, lidar, and Worldview-3 imagery to maximize detection of forested inundation extent in the Delmarva Peninsula, USA
By Melanie Vanderhoof (GECSC), Hayley Distler (GECSC), Di Ana Mendiola (GECSC), and Megan Lang. Published by Remote Sensing.
Natural variability in surface-water extent presents a challenge to gathering timely, accurate information, particularly in environments that are dominated by small and/or forested wetlands. This study mapped inundation extent across a watershed (located in Maryland and Delaware) dominated by both small and forested wetlands. Inundation was mapped using synthetic aperture radar (SAR) imagery from Radarsat-2 and high-resolution imagery collected by Worldview-3. The results suggest that integrating SAR imagery with fine-resolution, multispectral imagery can improve surface water maps. Further, it suggests that depressions, mapped using a lidar DEM can be used to improve confidence and reduce error in surface water maps.