A Changing Hydrological Regime: Trends in Magnitude and Timing of Glacier Ice Melt and Glacier Runoff in a High Latitude Coastal Watershed

With a unique biogeophysical signature relative to other freshwater sources, meltwater from glaciers plays a crucial role in the hydrological and ecological regime of high latitude coastal areas. Today, as glaciers worldwide exhibit persistent negative mass balance, glacier runoff is changing in both magnitude and timing, with potential downstream impacts on infrastructure, ecosystems, and ecosystem resources. However, runoff trends may be difficult to detect in coastal systems with large precipitation variability. Here, we use the coupled energy balance and water routing model SnowModel-HydroFlow to examine changes in timing and magnitude of runoff from the western Juneau Icefield in Southeast Alaska between 1980 and 2016. We find that under sustained glacier mass loss (−0.57 ± 0.12 m w. e. a−1), several hydrological variables related to runoff show increasing trends. This includes annual and spring glacier ice melt volumes (+10% and +16% decade−1) which, because of higher proportions of precipitation, translate to smaller increases in glacier runoff (+3% and +7% decade−1) and total watershed runoff (+1.4% and +3% decade−1). These results suggest that the western Juneau Icefield watersheds are still in an increasing glacier runoff period prior to reaching “peak water.” In terms of timing, we find that maximum glacier ice melt is occurring earlier (2.5 days decade−1), indicating a change in the source and quality of freshwater being delivered downstream in the early summer. Our findings highlight that even in maritime climates with large precipitation variability, high latitude coastal watersheds are experiencing hydrological regime change driven by ongoing glacier mass loss.The authors would like to thank W. P. Dryer, C. McNeil, S. Candela, and J. Pierce for help in the field. R. Crumley and C. Cosgrove assisted with SnowModel initialization. The Juneau Icefield Research Program (JIRP) provided field data and logistical support. E. Berthier provided geodetic data, F. Ziemen contributed model results, and C. McNeil provided assistance with datasets on behalf of both USGS and JIRP. The authors thank three anonymous reviewers for suggestions that have greatly improved the manuscript. This work was supported by a Department of Interior Alaska Climate Adaptation Science Center graduate fellowship awarded under Cooperative Agreement G17AC00213, by NASA under award NASANNX16AQ88G, by the National Science Foundation under award OIA-1208927 and by the State of Alaska (Experimental Program for Stimulating Competitive Research–Alaska Adapting to Changing Environments award), and by the University of Alaska Fairbanks Resilience and Adaptation Program. The authors acknowledge that field work was conducted on the traditional and unceded lands of the Lingit Aani (Tlingit), Michif Piyii (Métis), and Dënéndeh nations.Ye

Iceberg topography and volume classification using TanDEM-X interferometry

Icebergs in polar regions affect water salinity, alter marine habitats, and impose serious hazards on maritime operations and navigation. These impacts mainly depend on the iceberg volume, which remains an elusive parameter to measure. We investigate the capability of TanDEM-X bistatic single-pass synthetic aperture radar interferometry (InSAR) to derive iceberg subaerial morphology and infer total volume. We cross-verify InSAR results with Operation IceBridge (OIB) data acquired near Wordie Bay, Antarctica, as part of the OIB/TanDEM-X Antarctic Science Campaign (OTASC). While icebergs are typically classified according to size based on length or maximum height, we develop a new volumetric classification approach for applications where iceberg volume is relevant. For icebergs with heights exceeding 5 m, we find iceberg volumes derived from TanDEM-X and OIB data match within 7 %. We also derive a range of possible iceberg keel depths relevant to grounding and potential impacts on subsea installations. These results suggest that TanDEM-X could pave the way for future single-pass interferometric systems for scientific and operational iceberg mapping and classification based on iceberg volume and keel depth

Circumpolar Deep Water Impacts Glacial Meltwater Export and Coastal Biogeochemical Cycling Along the West Antarctic Peninsula

Warming along the Antarctic Peninsula has led to an increase in the export of glacial meltwater to the coastal ocean. While observations to date suggest that this freshwater export acts as an important forcing on the marine ecosystem, the processes linking ice–ocean interactions to lower trophic-level growth, particularly in coastal bays and fjords, are poorly understood. Here, we identify salient hydrographic features in Barilari Bay, a west Antarctic Peninsula fjord influenced by warm modified Upper Circumpolar Deep Water. In this fjord, interactions between the glaciers and ocean act as a control on coastal circulation, contributing to the redistribution of water masses in an upwelling plume and a vertical flux of nutrients toward the euphotic zone. This nutrient-rich plume, containing glacial meltwater but primarily composed of ambient ocean waters including modified Upper Circumpolar Deep Water, spreads through the fjord as a 150-m thick layer in the upper water column. The combination of meltwater-driven stratification, long residence time of the surface plume owing to weak circulation, and nutrient enrichment promotes phytoplankton growth within the fjord, as evidenced by shallow phytoplankton blooms and concomitant nutrient drawdown at the fjord mouth in late February. Gradients in meltwater distributions are further paralleled by gradients in phytoplankton and benthic community composition. While glacial meltwater export and upwelling of ambient waters in this way contribute to elevated primary and secondary productivity, subsurface nutrient enhancement of glacially modified ocean waters suggests that a portion of these macronutrients, as well any iron upwelled or input in meltwater, are exported to the continental shelf. Sustained atmospheric warming in the coming decades, contributing to greater runoff, would invigorate the marine circulation with consequences for glacier dynamics and biogeochemical cycling within the fjord. We conclude that ice–ocean interactions along the Antarctic Peninsula margins act as an important control on coastal marine ecosystems, with repercussions for carbon cycling along the west Antarctic Peninsula shelf as a whole

Northwest Greenland Active Source Seismic Experiment

Line Starting Position (lat/long): 78.05494 -68.43001 Line Ending Position (lat/long): 78.06791 -68.36563In summer of 2018, the Seismometer to Investigate Ice and Ocean Structure (SIIOS) team conducted a geophysical field investigation on the Greenland ice sheet in northwestern Greenland at a location where a previous airborne radar survey by Palmer et al. (2013) had detected the signatures of a subglacial lake. The field site is located approximately 50 km north of the town of Qaanaaq. This site was chosen for the SIIOS project as it provides an opportunity for studying how a lander station could be used to detect subsurface water at an icy-ocean world. The purpose of the investigation was to confirm the presence of the subglacial lake and to measure its physical properties such as seismic impedance, as well as to estimate its depth and volume. One component of the investigation consisted of an active source seismic survey that was used to create a reflection image of the lake, as well as to measure the ice-bottom reflection coefficient. The survey was conducted along a roughly northeast oriented traverse, which started above the subglacial lake and crossed the lake’s eastern boundary.Funding for this work was provided by the NASA Planetary Science and Technology Through Analog Research (PSTAR) Grant # 80NSSC17K0229

Seismometer to Investigate Ice and Ocean Structure (SIIOS)

No abstract availabl

Ocean variability beneath Thwaites Eastern Ice Shelf driven by the Pine Island Bay Gyre strength

West Antarctic ice-shelf thinning is primarily caused by ocean-driven basal melting. Here we assess ocean variability below Thwaites Eastern Ice Shelf (TEIS) and reveal the importance of local ocean circulation and sea-ice. Measurements obtained from two sub-ice-shelf moorings, spanning January 2020 to March 2021, show warming of the ice-shelf cavity and an increase in meltwater fraction of the upper sub-ice layer. Combined with ocean modelling results, our observations suggest that meltwater from Pine Island Ice Shelf feeds into the TEIS cavity, adding to horizontal heat transport there. We propose that a weakening of the Pine Island Bay gyre caused by prolonged sea-ice cover from April 2020 to March 2021 allowed meltwater-enriched waters to enter the TEIS cavity, which increased the temperature of the upper layer. Our study highlights the sensitivity of ocean circulation beneath ice shelves to local atmosphere-sea-ice-ocean forcing in neighbouring open oceans

SIIOS in Alaska: Testing an "In-Vault" Option for a Europa Lander Seismometer Experiment

The icy moons of Europa and Enceladus are thought to have global subsurface oceans in contact with mineral-rich silicate interiors, likely providing the three ingredients needed for life as we know it: liquid water, essential chemicals, and a source of energy. The possibility of life forming in their subsurface oceans relies in part on transfer of oxidants from the irradiated ice surface to the sheltered ocean below. Constraining the mechanisms and location of material exchange between the ice surface, the ice shell, and the subsurface ocean, however, is not possible without knowledge of ice thickness and liquid water depths. In a future lander-based experiment seismic measurements will be a key geophysical tool for obtaining this critical knowledge. The Seismometer to Investigate Ice and Ocean Structure (SIIOS) field-tests flight-ready technologies and develops the analytical methods necessary to make a seismic study of Europa and Enceladus a reality. We have been performing small-array seismology with a flight-candidate sensor in analog environments that exploit passive sources. Determining the depth to a subsurface ocean and any intermediate bodies of water is a priority for Ocean Worlds missions as it allows assessment of the habitability of these worlds and provides vital information for evaluating the spacecraft technologies required to access their oceans