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Anthony Arendt

Research Scientist/Engineer - Senior

Email

arendta@apl.washington.edu

Phone

206-685-4551

Department Affiliation

Polar Science Center

Education

B.S. Earth & Atmospheric Sciences, University of Alberta, 1995

M.S. Earth & Atmospheric Sciences, University of Alberta, 1997

Ph.D. Geophysics, University of Alaska, 2006

Publications

2000-present and while at APL-UW

Hypsometric control on glacier mass balance sensitivity in Alaska and northwest Canada

McGrath, D., L. Sass, S. O'Neel, A. Arendt, and C. Kienholz, "Hypsometric control on glacier mass balance sensitivity in Alaska and northwest Canada," Earth's Future, 5, 324-336, doi:10.1002/2016EF000479, 2017.

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1 Mar 2017

Glacier hypsometry provides a first-order approach for assessing a glacier's response to climate forcings. We couple the Randolph Glacier Inventory to a suite of in situ observations and climate model output to examine potential change for the ~27,000 glaciers in Alaska and northwest Canada through the end of the 21st century. By 2100, based on Representative Concentration Pathways (RCPs) 4.5–8.5 forcings, summer temperatures are predicted to increase between +2.1 and +4.6°C, while solid precipitation (snow) is predicted to decrease by –6 to –11%, despite a +9 to +21% increase in total precipitation. Snow is predicted to undergo a pronounced decrease in the fall, shifting the start of the accumulation season back by ~1 month. In response to these forcings, the regional equilibrium line altitude (ELA) may increase by +105 to +225 m by 2100. The mass balance sensitivity to this increase is highly variable, with the most substantive impact for glaciers with either limited elevation ranges (often small (<1 km2) glaciers, which account for 80% of glaciers in the region) or those with top-heavy geometries, like icefields. For more than 20% of glaciers, future ELAs, given RCP 6.0 forcings, will exceed the maximum elevation of the glacier, resulting in their eventual demise, while for others, accumulation area ratios will decrease by >60%. Our results highlight the first-order control of hypsometry on individual glacier response to climate change, and the variability that hypsometry introduces to a regional response to a coherent climate perturbation.

High-resolution modeling of coastal freshwater discharge and glacier mass balance in the Gulf of Alaska watershed

Beamer, J.P., D.F. Hill, A. Arendt, and G.E. Liston, "High-resolution modeling of coastal freshwater discharge and glacier mass balance in the Gulf of Alaska watershed," Water Resour. Res., 52, 3888-3909, doi:10.1002/2015WR018457, 2016.

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1 May 2016

A comprehensive study of the Gulf of Alaska (GOA) drainage basin was carried out to improve understanding of the coastal freshwater discharge (FWD) and glacier volume loss (GVL). Hydrologic processes during the period 1980–2014 were modeled using a suite of physically based, spatially distributed weather, energy-balance snow/ice melt, soil water balance, and runoff routing models at a high-resolution (1 km horizontal grid; daily time step). Meteorological forcing was provided by the North American Regional Reanalysis (NARR), Modern Era Retrospective Analysis for Research and Applications (MERRA), and Climate Forecast System Reanalysis (CFSR) data sets. Streamflow and glacier mass balance modeled using MERRA and CFSR compared well with observations in four watersheds used for calibration in the study domain. However, only CFSR produced regional seasonal and long-term trends in water balance that compared favorably with independent Gravity Recovery and Climate Experiment (GRACE) and airborne altimetry data. Mean annual runoff using CFSR was 760 km3 yr−1, 8% of which was derived from the long-term removal of stored water from glaciers (glacier volume loss). The annual runoff from CFSR was partitioned into 63% snowmelt, 17% glacier ice melt, and 20% rainfall. Glacier runoff, taken as the sum of rainfall, snow, and ice melt occurring each season on glacier surfaces, was 38% of the total seasonal runoff, with the remaining runoff sourced from nonglacier surfaces. Our simulations suggests that existing GRACE solutions, previously reported to represent glacier mass balance alone, are actually measuring the full water budget of land and ice surfaces.

End-of-winter snow depth variability on glaciers in Alaska

McGrath, D., L. Sass, S. O'Neel, A. Arendt, G. Wolken, A. Gusmeroli, C. Reinholz, and C. McNeil, "End-of-winter snow depth variability on glaciers in Alaska," J. Geophys. Res., 120, 1530-1550, doi:10.1002/2015JF003539, 2015.

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18 Aug 2015

A quantitative understanding of snow thickness and snow water equivalent (SWE) on glaciers is essential to a wide range of scientific and resource management topics. However, robust SWE estimates are observationally challenging, in part because SWE can vary abruptly over short distances in complex terrain due to interactions between topography and meteorological processes. In spring 2013, we measured snow accumulation on several glaciers around the Gulf of Alaska using both ground- and helicopter-based ground-penetrating radar surveys, complemented by extensive ground truth observations. We found that SWE can be highly variable (40% difference) over short spatial scales (tens to hundreds of meters), especially in the ablation zone where the underlying ice surfaces are typically rough. Elevation provides the dominant basin-scale influence on SWE, with gradients ranging from 115 to 400 mm/100 m. Regionally, total accumulation and the accumulation gradient are strongly controlled by a glacier's distance from the coastal moisture source. Multiple linear regressions, used to calculate distributed SWE fields, show that robust results require adequate sampling of the true distribution of multiple terrain parameters. Final SWE estimates (comparable to winter balances) show reasonable agreement with both the Parameter-elevation Relationships on Independent Slopes Model climate data set (9–36% difference) and the U.S. Geological Survey Alaska Benchmark Glaciers (6–36% difference). All the glaciers in our study exhibit substantial sensitivity to changing snow-rain fractions, regardless of their location in a coastal or continental climate. While process-based SWE projections remain elusive, the collection of ground-penetrating radar (GPR)-derived data sets provides a greatly enhanced perspective on the spatial distribution of SWE and will pave the way for future work that may eventually allow such projections.

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In The News

NASA High Mountain Asia Project

eScience Institute

Over one billion people live downstream of the region referred to as High Mountain Asia, an area ranging from the Hindu Kush and Tien Shan in the west to the Eastern Himalaya, and home to “the world’s largest reservoir of perennial glaciers and snow outside of the Earth’s polar ice sheets”. The High Mountain Asia (HMA) Project, led by Anthony Arendt, eScience senior data science fellow and senior research scientist with the UW Polar Science Center at the Applied Physics Laboratory, aims to “generate knowledge on how climate change is impacting the water resources of that region.”

25 Jul 2017

Alaska glaciers sending 75 billion tons of water into sea each year

CBS News, Michael Casey

Glaciers in Alaska often get second billing to the mountains of ice in the Himalayas or those in Patagonia. But a new study out Wednesday suggests these glaciers are suffering the same fate as their more famous brethren and are already punching far above their weight when it comes to their contribution to sea level rise.

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18 Jun 2015

Mountain glaciers comprise a small and widely distributed fraction of the world's terrestrial ice, yet their rapid losses presently drive a large percentage of the cryosphere's contribution to sea level rise. Regional mass balance assessments are challenging over large glacier populations due to remote and rugged geography, variable response of individual glaciers to climate change, and episodic calving losses from tidewater glaciers. In Alaska, we use airborne altimetry from 116 glaciers to estimate a regional mass balance of –75±11 Gt yr-1 (1994–2013). Our glacier sample is spatially well-distributed, yet pervasive variability in mass balances obscures geospatial and climatic relationships. However, for the first time, these data allow the partitioning of regional mass balance by glacier type. We find that tidewater glaciers are losing mass at substantially slower rates than other glaciers in Alaska and collectively contribute to only 6% of the regional mass loss.

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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