Melt water input from the Bering Glacier watershed into the Gulf of Alaska

The annual runoff from the melting of large glaciers and snow fields along the northern perimeter of the Gulf of Alaska is a critical component of marine physical and biological systems; yet, most of this freshwater is not measured. Here we show estimates of melt for the watershed that contains the largest and longest glacier in North America, the Bering Glacier. The procedure combines in situ observations of snow and ice melt acquired by a long-term monitoring program, multispectral satellite observations, and nearby temperature measurements. The estimated melt is 40 km3 per melt season, ± 3.0 km3, observed over the decadal period, 2002–2012. As a result of climate change, these estimates could increase to 60 km3/yr by 2050. This technique and the derived melt coefficients can be applied to estimate melt from Alaska to Washington glaciers

Changes in mass balance of South Cascade Glacier, North Cascades, 1959 to 1994

EXTRACT (SEE PDF FOR FULL ABSTRACT): Annual, winter, and summer mass balance measurements at South Cascade Glacier in the North Cascade Mountains of Washington State constitute a continuous time series 36 years long, from 1959 to 1994. ... The long-term trends at South Cascade Glacier are decreased winter accumulation and increased summer ablation, neither of which is conducive to glacier growth, so the trend in the Pacific Northwest is clearly away from an ice-age type of climate at the current time. The data also demonstrate that a glaciologically significant long-term change in snow precipitation can occur rapidly, in as short an interval as 1 year, much more rapidly than changes in temperature

Satellite passive microwave observations of the upper Colorado River snowpack

Seasonal snow cover in the mountains of the Upper Colorado River Basin is a major source of water for a large portion of the southwestern United States. The extent and amount of this snowpack not only reflects changes in weather patterns and climate but also influences the general circulation through modification of the energy exchange between land and atmosphere. ... Satellite observations and remote sensing techniques can enhance the standard snowpack observations to provide the temporal and spatial measurements required for understanding the role of snow in the surface energy balance and improving the management of water resources

Multistate resistive switching memory for synaptic memory applications

Reproducible low bias bipolar resistive switching memory in HfZnOx based memristors is reported. The modification of the concentration of oxygen vacancies in the ternary oxide film, which is facilitated by adding ZnO into HfO2, results in improved memory operation by the ternary oxide compared to the single binary oxides. A controlled multistate memory operation is achieved by controlling current compliance and RESET stop voltages. A high DC cyclic stability up to 400 cycles in the multistate memory performance is observed. Conventional synaptic operation in terms of potentiation, depression plasticity, and Ebbinghaus forgetting process are also studied. The memory mechanism is shown to originate from the migration of the oxygen vacancies and modulation of the interfacial layers

Comparing satellite and helicopter-based methods for observing crevasses, application in East Antarctica

Knowing where crevasses are is critical for planning safe on-ice field operations. Previous methods have ranged from real-time imaging of subsurface structures using ground penetrating radar, to mapping of crevasses over large areas using satellite imagery, with each method having it\u27s own strengths and weaknesses. In this paper we compare the detection of crevasses at the Totten Glacier, East Antarctica, from helicopter-borne ground penetrating radar with satellite-based microwave synthetic aperture radar imagery. Our results show that the 80 MHz helicopter-borne ground penetrating radar was able to detect crevasses up to a depth of 70 m, with snow bridge thickness of \u3e30 m. Comparison with TerraSAR-X (X-band, 9.6 GHz) satellite imagery indicates that the latter is highly effective, detecting 100% of crevasses with snow bridges of up to 4m thick and detecting 95% of crevasses with snow bridges up to 10 m thick. The ability of both methods to identify individual crevasses is affected by several factors including crevasse geometry, survey or satellite orientation and snow moisture content, and further experiments are planned to investigate performance under a wider range of conditions

Contribution of Alaskan glaciers to sea level rise derived from satellite imagery

International audienceOver the last 50 years, retreating glaciers and ice caps (GIC) contributed 0.5 mm/yr to sea level rises (SLR), and one third is believed to originate from ice masses bordering the Gulf of Alaska. However, these estimates of ice wastage in Alaska are based on methods that measure a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others. How these methods capture the complex pattern of decadal elevation changes at the scale of individual glacier and mountain range is unclear. Here, combining a comprehensive glacier inventory with elevation changes derived from sequential digital elevation models (DEMs), we found that, between 1962 and 2006, Alaskan glaciers lost 41.9 ± 8.6 km**3/yr water equivalent (w.e.) and contributed 0.12±0.02 mm/yr to SLR. Our ice loss is 34% lower than previous estimates. Reasons for our lower values include the higher spatial resolution of our glacier inventory and the reduction of ice thinning under debris and at the glacier margins which were not resolved in earlier work. Estimates of mass loss from GIC in other mountain regions could be subject to similar revisions

Iceberg melting substantially modifies oceanic heat flux towards a major Greenlandic tidewater glacier

Fjord dynamics influence oceanic heat flux to the Greenland ice sheet. Submarine iceberg melting releases large volumes of freshwater within Greenland’s fjords, yet its impact on fjord dynamics remains unclear. We modify an ocean model to simulate submarine iceberg melting in Sermilik Fjord, east Greenland. Here we find that submarine iceberg melting cools and freshens the fjord by up to ~5 °C and 0.7 psu in the upper 100-200 m. The release of freshwater from icebergs drives an overturning circulation, resulting in a ~10% increase in net up-fjord heat flux. In addition, we find that submarine iceberg melting accounts for over 95% of heat used for ice melt in Sermilik Fjord. Our results highlight the substantial impact that icebergs have on the dynamics of a major Greenlandic fjord, demonstrating the importance of including related processes in studies that seek to quantify interactions between the ice sheet and the ocean