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Abstract. The McMurdo Dry Valleys (MDV) are home to a unique microbial ecosystem that is dependent on the availability of freshwater. This is a polar desert and freshwater originates almost entirely from surface and near-surface melt of the cold-based glaciers. Understanding the future evolution of these environments requires the simulation of the full chain of physical processes from net radiative forcing, surface energy balance, melt, runoff and transport of meltwater in stream channels from the glaciers to the terminal lakes where the microbial community resides. To establish a new framework to do this, we present the first application of WRF-Hydro/Glacier in the MDV, which as a fully distributed hydrological model has the capability to resolve the streams from the glaciers to the bare land that surround them. Given that meltwater generation in the MDV is almost entirely dependent on small changes in the energy balance of the glaciers, the aim of this study is to optimize the multi-layer snowpack scheme that is embedded in WRF-Hydro/Glacier to ensure that the feedbacks between albedo, snowfall and melt are fully resolved. To achieve this, WRF-Hydro/Glacier is implemented at a point scale using automatic weather station data on Commonwealth Glacier to physically model the onset, duration and end of melt over a 7-month period (1 August 2021 to 28 February 2022). To resolve the limited energetics controlling melt, it was necessary to (1) limit the percolation of meltwater through the ice layers in the multi-layer snowpack scheme and (2) optimize the parameters controlling the albedo of both snow and ice over the melt season based on observed spectral signatures of albedo. These modifications enabled the variability of broadband albedo over the melt season to be accurately simulated and ensured that modelled surface and near-surface temperatures, surface height change and runoff were fully resolved. By establishing a new framework that couples a detailed snowpack model to a fully distributed hydrological model, this work provides a stepping stone to model the spatial and temporal variability of melt and streamflow in the future, which will enable some of the unknown questions about the hydrological connectivity of the MDV to be answered.
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The seasonal evolution of albedo across glaciers and the surrounding landscape of Taylor Valley, Antarctica
Abstract. The McMurdo Dry Valleys (MDVs) of Antarctica are a polar desertecosystem consisting of alpine glaciers, ice-covered lakes, streams, andexpanses of vegetation-free rocky soil. Because average summer temperaturesare close to 0 ∘C, theMDV ecosystem in general, and glacier melt dynamics in particular, are both closely linked to the energy balance. A slightincrease in incoming radiation or change in albedo can have large effects onthe timing and volume of meltwater. However, the seasonal evolution orspatial variability of albedo in the valleys has yet to fully characterized.In this study, we aim to understand the drivers of landscape albedo changewithin and across seasons. To do so, a box with a camera, GPS, andshortwave radiometer was hung from a helicopter that flew transects four to fivetimes a season along Taylor Valley. Measurements were repeated over threeseasons. These data were coupled with incoming radiation measured at sixmeteorological stations distributed along the valley to calculate thedistribution of albedo across individual glaciers, lakes, and soilsurfaces. We hypothesized that albedo would decrease throughout the australsummer with ablation of snow patches and increasing sediment exposure on theglacier and lake surfaces. However, small snow events (<6 mm waterequivalent) coupled with ice whitening caused spatial and temporalvariability of albedo across the entire landscape. Glaciers frequentlyfollowed a pattern of increasing albedo with increasing elevation, as well asincreasing albedo moving from east to west laterally across the ablationzone. We suggest that spatial patterns of albedo are a function of landscapemorphology trapping snow and sediment, longitudinal gradients in snowfallmagnitude, and wind-driven snow redistribution from east to west alongthe valley. We also compare our albedo measurements to the MODIS albedo productand found that overall the data have reasonable agreement. The mismatch inspatial scale between these two datasets results in variability, which isreduced after a snow event due to albedo following valley-scale gradients ofsnowfall magnitude. These findings highlight the importance of understandingthe spatial and temporal variability in albedo and the close coupling ofclimate and landscape response. This new understanding of landscape albedocan constrain landscape energy budgets, better predict meltwater generationon from MDV glaciers, and how these ecosystems will respond to changingclimate at the landscape scale.
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- Award ID(s):
- 1637708
- PAR ID:
- 10163380
- Date Published:
- Journal Name:
- The Cryosphere
- Volume:
- 14
- Issue:
- 3
- ISSN:
- 1994-0424
- Page Range / eLocation ID:
- 769 to 788
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/tc-14-769-2020
