scholarly journals Near-surface internal melting: a substantial mass loss on Antarctic Dry Valley glaciers

2014 ◽  
Vol 60 (220) ◽  
pp. 361-374 ◽  
Author(s):  
Matthew J. Hoffman ◽  
Andrew G. Fountain ◽  
Glen E. Liston
Keyword(s):  
Meteorological Data ◽  
Primary Source ◽  
Balance Model ◽  
Weathering Crust ◽  
Field Observations ◽  
Dry Valleys ◽  
Near Surface ◽  
Ice Surface ◽  
Dry Valley ◽  
Glacier Ablation

AbstractThe McMurdo Dry Valleys, southern Victoria Land, East Antarctica, are a polar desert, and melt from glacial ice is the primary source of water to streams, lakes and associated ecosystems. Previous work found that to adequately model glacier ablation and subsurface ice temperatures with a surface energy-balance model required including the transmission of solar radiation into the ice. Here we investigate the contribution of subsurface melt to the mass balance of (and runoff from) Dry Valley glaciers by including a drainage process in the model and applying the model to three glacier sites using 13 years of hourly meteorological data. Model results for the smooth glacier surfaces common to many glaciers in the Dry Valleys showed that sublimation was typically the largest component of surface lowering, with rare episodes of surface melting, consistent with anecdotal field observations. Results also showed extensive internal melting 5–15 cm below the ice surface, the drainage of which accounted for ~50% of summer ablation. This is consistent with field observations of subsurface streams and formation of a weathering crust. We identify an annual cycle of weathering crust formation in summer and its removal during the 10 months of winter sublimation.

scholarly journals Observations of snowdrift over Antarctic snow and blue-ice surfaces

2001 ◽  
Vol 32 ◽  
pp. 168-174 ◽  
Author(s):  
Richard Bintanja ◽  
H. Lilienthal ◽  
H. Tüg
Keyword(s):  
Meteorological Data ◽  
Austral Summer ◽  
Vertical Profiles ◽  
Near Surface ◽  
Ice Surface ◽  
Antarctic Snow ◽  
Drift Density ◽  
Weak Winds ◽  
Vertical Gradients ◽  
Surface Drift

AbstractVertical profiles of snowdrift density and concurrent meteorological data were measured over Antarctic snow and blue ice during a 1 month field experiment in austral summer 1997/98. It is found that drift densities and transport rates over blue ice are significantly smaller than over snow, which can be attributed mainly to the limited availability of snow particles at the blue-ice surface. Hence, over blue ice, near-surface drift densities and vertical gradients in drift density are relatively small. Over blue ice, snowdrift can occur in very weak winds, presumably because of the smoothness of the surface. Over snow, in contrast, drift occurs only in much stronger winds, such that the shear stress applied by the flow can overcome the cohesive interparticle bonds.

scholarly journals Seasonally stable temperature gradients through supraglacial debris in the Everest region of Nepal, Central Himalaya

2020 ◽  
pp. 1-12
Author(s):  
Ann V. Rowan ◽  
Lindsey I. Nicholson ◽  
Duncan J. Quincey ◽  
Morgan J. Gibson ◽  
Tristram D.L. Irvine-Fynn ◽  
...  
Keyword(s):  
Mass Balance ◽  
Monsoon Season ◽  
Temperature Gradients ◽  
Glacier Mass Balance ◽  
Central Himalaya ◽  
Atmospheric Conditions ◽  
Near Surface ◽  
Ice Surface ◽  
Glacier Ablation ◽  
The Impact

Abstract Rock debris covers ~30% of glacier ablation areas in the Central Himalaya and modifies the impact of atmospheric conditions on mass balance. The thermal properties of supraglacial debris are diurnally variable but remain poorly constrained for monsoon-influenced glaciers over the timescale of the ablation season. We measured vertical debris profile temperatures at 12 sites on four glaciers in the Everest region with debris thickness ranging from 0.08 to 2.8 m. Typically, the length of the ice ablation season beneath supraglacial debris was 160 days (15 May to 22 October)—a month longer than the monsoon season. Debris temperature gradients were approximately linear (r2 > 0.83), measured as −40°C m–1 where debris was up to 0.1 m thick, −20°C m–1 for debris 0.1–0.5 m thick, and −4°C m–1 for debris greater than 0.5 m thick. Our results demonstrate that the influence of supraglacial debris on the temperature of the underlying ice surface, and therefore melt, is stable at a seasonal timescale and can be estimated from near-surface temperature. These results have the potential to greatly improve the representation of ablation in calculations of debris-covered glacier mass balance and projections of their response to climate change.

scholarly journals Evolution of cryoconite holes and their contribution to meltwater runoff from glaciers in the McMurdo Dry Valleys, Antarctica

2004 ◽  
Vol 50 (168) ◽  
pp. 35-45 ◽  
Author(s):  
Andrew G. Fountain ◽  
Martyn Tranter ◽  
Thomas H. Nylen ◽  
Karen J. Lewis ◽  
Derek R. Mueller
Keyword(s):  
Water Levels ◽  
Mcmurdo Dry Valleys ◽  
Dry Valleys ◽  
Glacier Surface ◽  
Near Surface ◽  
Ice Melt ◽  
Ice Surface ◽  
Meltwater Runoff ◽  
Hydrologic System ◽  
Chloride Accumulation

AbstractCryoconite holes are water-filled holes in the surface of a glacier caused by enhanced ice melt around trapped sediment. Measurements on the ablation zones of four glaciers in Taylor Valley, Antarctica, show that cryoconite holes cover about 4–6% of the ice surface. They typically vary in diameter from 5 to 145 cm, with depths ranging from 4 to 56 cm. In some cases, huge holes form with 5 m depths and 30 m diameters. Unlike cryoconite holes elsewhere, these have ice lids up to 36 cm thick and melt from within each spring. About one-half of the holes are connected to the near-surface hydrologic system and the remainder are isolated. The duration of isolation, estimated from the chloride accumulation in hole waters, commonly shows ages of several years, with one hole of 10 years. The cryoconite holes in the McMurdo Dry Valleys create a near-surface hydrologic system tens of cm below the ice surface. The glacier surface itself is generally frozen and dry. Comparison of water levels between holes a few meters apart shows independent cycles of water storage and release. Most likely, local freeze–thaw effects control water passage and therefore temporary storage. Rough calculations indicate that the holes generate at least 13% of the observed runoff on the one glacier measured. This hydrologic system represents the transition between a melting ice cover with supraglacial streams and one entirely frozen and absent of water.

A Review of the Dry Valley Drilling Project, 1971–76

Polar Record ◽  
1981 ◽  
Vol 20 (129) ◽  
pp. 533-541 ◽  
Author(s):  
Tetsuya Torii
Keyword(s):  
The United States ◽  
Volcanic Complex ◽  
Dry Valleys ◽  
Geological History ◽  
Mcmurdo Sound ◽  
Near Surface ◽  
Unconsolidated Material ◽  
Dry Valley ◽  
Logistic Support ◽  
Drilling Project

The Dry Valleys of southern Victoria Land, Antarctica, lying some 75 km west of McMurdo station, form an arid, ice-free area of roughly 2 500 km2. Since the late 1950s, this region has provided a remarkable opportunity for geoscientific studies of the exposed surface rocks, within easy reach of logistic support at McMurdo and Scott bases on Ross Island (Fig 1). As a result of a study of Lake Vanda in the Wright Valley, which began during the 1963–64 summer field season, scientists from the United States, New Zealand and Japan supported the view that further advances in our knowledge of the Dry Valleys would require an examination of the unconsolidated material, and the geothermal regime at lake sites, using direct shallow drilling techniques. As drilling techniques and interestin the geological history of the McMurdo region as a whole (encompassing the Transantarctic Mountains, Ross Island, McMurdo Sound and the Dry Valleys) developed, an international, multidisciplinary project—the Dry Valley Drilling Project (DVDP)—was conceived. By 1969 the US National Science Foundation (NSF) had decided to coordinate proposals from scientists wishing to drill the first intermediate and deep cores into the sediment and rock of Antarctica; the aim, a reconstruction of Antarctic geological history that traditional surface or near-surface studies alone could never achieve. Initially, the approach was to be a sub-surface physical, chemical and biological examination of theDry Valleys, but as the project developed it encompassed studies of the Ross Island volcanic complex and McMurdo Sound sediments.

scholarly journals Using climate reanalysis data in conjunction with multi-temporal satellite thermal imagery to derive supraglacial debris thickness changes from energy-balance modelling

2021 ◽  
pp. 1-19
Author(s):  
Rebecca L. Stewart ◽  
Matthew Westoby ◽  
Francesca Pellicciotti ◽  
Ann Rowan ◽  
Darrel Swift ◽  
...  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Current Knowledge ◽  
Meteorological Data ◽  
Reanalysis Data ◽  
Balance Model ◽  
Thermal Imagery ◽  
Thickness Estimation ◽  
Miage Glacier

Abstract Surface energy-balance models are commonly used in conjunction with satellite thermal imagery to estimate supraglacial debris thickness. Removing the need for local meteorological data in the debris thickness estimation workflow could improve the versatility and spatiotemporal application of debris thickness estimation. We evaluate the use of regional reanalysis data to derive debris thickness for two mountain glaciers using a surface energy-balance model. Results forced using ERA-5 agree with AWS-derived estimates to within 0.01 ± 0.05 m for Miage Glacier, Italy, and 0.01 ± 0.02 m for Khumbu Glacier, Nepal. ERA-5 data were then used to estimate spatiotemporal changes in debris thickness over a ~20-year period for Miage Glacier, Khumbu Glacier and Haut Glacier d'Arolla, Switzerland. We observe significant increases in debris thickness at the terminus for Haut Glacier d'Arolla and at the margins of the expanding debris cover at all glaciers. While simulated debris thickness was underestimated compared to point measurements in areas of thick debris, our approach can reconstruct glacier-scale debris thickness distribution and its temporal evolution over multiple decades. We find significant changes in debris thickness over areas of thin debris, areas susceptible to high ablation rates, where current knowledge of debris evolution is limited.

scholarly journals Sensitivity of groundwater recharge using climatic analogues and HYDRUS-1D

2012 ◽  
Vol 16 (8) ◽  
pp. 2485-2497 ◽  
Author(s):  
B. Leterme ◽  
D. Mallants ◽  
D. Jacques
Keyword(s):  
Water Balance ◽  
Groundwater Recharge ◽  
Potential Evapotranspiration ◽  
Future Climate ◽  
Annual Precipitation ◽  
Balance Model ◽  
Subtropical Climate ◽  
Northern Spain ◽  
Near Surface ◽  
Hydrus 1D

Abstract. The sensitivity of groundwater recharge to different climate conditions was simulated using the approach of climatic analogue stations, i.e. stations presently experiencing climatic conditions corresponding to a possible future climate state. The study was conducted in the context of a safety assessment of a future near-surface disposal facility for low and intermediate level short-lived radioactive waste in Belgium; this includes estimation of groundwater recharge for the next millennia. Groundwater recharge was simulated using the Richards based soil water balance model HYDRUS-1D and meteorological time series from analogue stations. This study used four analogue stations for a warmer subtropical climate with changes of average annual precipitation and potential evapotranspiration from −42% to +5% and from +8% to +82%, respectively, compared to the present-day climate. Resulting water balance calculations yielded a change in groundwater recharge ranging from a decrease of 72% to an increase of 3% for the four different analogue stations. The Gijon analogue station (Northern Spain), considered as the most representative for the near future climate state in the study area, shows an increase of 3% of groundwater recharge for a 5% increase of annual precipitation. Calculations for a colder (tundra) climate showed a change in groundwater recharge ranging from a decrease of 97% to an increase of 32% for four different analogue stations, with an annual precipitation change from −69% to −14% compared to the present-day climate.

scholarly journals Climate pattern-scaling set for an ensemble of 22 GCMs – adding uncertainty to the IMOGEN version 2.0 impact system

2018 ◽  
Vol 11 (2) ◽  
pp. 541-560 ◽  
Author(s):  
Przemyslaw Zelazowski ◽  
Chris Huntingford ◽  
Lina M. Mercado ◽  
Nathalie Schaller
Keyword(s):  
Climate Change ◽  
Relative Humidity ◽  
Land Surface ◽  
Land Surface Model ◽  
Individual Performance ◽  
Balance Model ◽  
Surface Model ◽  
Near Surface ◽  
Global Circulation Models ◽  
Version 2.0

Abstract. Global circulation models (GCMs) are the best tool to understand climate change, as they attempt to represent all the important Earth system processes, including anthropogenic perturbation through fossil fuel burning. However, GCMs are computationally very expensive, which limits the number of simulations that can be made. Pattern scaling is an emulation technique that takes advantage of the fact that local and seasonal changes in surface climate are often approximately linear in the rate of warming over land and across the globe. This allows interpolation away from a limited number of available GCM simulations, to assess alternative future emissions scenarios. In this paper, we present a climate pattern-scaling set consisting of spatial climate change patterns along with parameters for an energy-balance model that calculates the amount of global warming. The set, available for download, is derived from 22 GCMs of the WCRP CMIP3 database, setting the basis for similar eventual pattern development for the CMIP5 and forthcoming CMIP6 ensemble. Critically, it extends the use of the IMOGEN (Integrated Model Of Global Effects of climatic aNomalies) framework to enable scanning across full uncertainty in GCMs for impact studies. Across models, the presented climate patterns represent consistent global mean trends, with a maximum of 4 (out of 22) GCMs exhibiting the opposite sign to the global trend per variable (relative humidity). The described new climate regimes are generally warmer, wetter (but with less snowfall), cloudier and windier, and have decreased relative humidity. Overall, when averaging individual performance across all variables, and without considering co-variance, the patterns explain one-third of regional change in decadal averages (mean percentage variance explained, PVE, 34.25±5.21), but the signal in some models exhibits much more linearity (e.g. MIROC3.2(hires): 41.53) than in others (GISS_ER: 22.67). The two most often considered variables, near-surface temperature and precipitation, have a PVE of 85.44±4.37 and 14.98±4.61, respectively. We also provide an example assessment of a terrestrial impact (changes in mean runoff) and compare projections by the IMOGEN system, which has one land surface model, against direct GCM outputs, which all have alternative representations of land functioning. The latter is noted as an additional source of uncertainty. Finally, current and potential future applications of the IMOGEN version 2.0 modelling system in the areas of ecosystem modelling and climate change impact assessment are presented and discussed.

scholarly journals Reconstruction of the annual balance of Vadret da Morteratsch, Switzerland, since 1865

2009 ◽  
Vol 50 (50) ◽  
pp. 126-134 ◽  
Author(s):  
Johanna Nemec ◽  
Philippe Huybrechts ◽  
Oleg Rybak ◽  
Johannes Oerlemans
Keyword(s):  
Meteorological Data ◽  
Balance Model ◽  
Surface Energy Fluxes ◽  
Temperature And Precipitation ◽  
Continuous Mass ◽  
Weather Stations ◽  
Precipitation Records ◽  
High Elevations ◽  
Annual Balance ◽  
Almost Continuous

AbstractWe have reconstructed the annual balance of Vadret da Morteratsch, Engadine, Switzerland, with a two-dimensional energy-balance model for the period 1865–2005. The model takes into account a parameterization of the surface energy fluxes, an albedo that decreases exponentially with snow depth as well as the shading effect of the surrounding mountains. The model was first calibrated with a 5 year record of annual balance measurements made at 20 different sites on the glacier between 2001 and 2006 using meteorological data from surrounding weather stations as input. To force the model for the period starting in 1865, we employed monthly temperature and precipitation records from nearby valley stations. The model reproduces the observed annual balance reasonably well, except for the lower part during the warmest years. Most crucial to the results is the altitudinal precipitation gradient, but this factor is hard to quantify from the limited precipitation data at high elevations. The simulation shows an almost continuous mass loss since 1865, with short interruptions around 1920, 1935 and 1980. A trend towards a more negative annual balance can be observed since the beginning of the 1980s. The simulated cumulative mass balance for the entire period 1865–2005 was found to be –46mw.e.

Physical properties and spatial distribution of the sea ice surface layer (SSL/snow) during the autumn phase of the MOSAiC expedition

2021 ◽  
Author(s):  
Ruzica Dadic ◽  
Martin Schneebeli ◽  
Henna-Reeta Hannula ◽  
Amy Macfarlane ◽  
Roberta Pirazzini
Keyword(s):  
Surface Layer ◽  
Spatial Distribution ◽  
Sea Ice ◽  
Physical Properties ◽  
Surface Scattering ◽  
Climate Feedback ◽  
Energy Fluxes ◽  
Scattering Layer ◽  
Near Surface ◽  
Ice Surface

<p>Snow cover dominates the thermal and optical properties of sea ice and the energy fluxes between the ocean and the atmosphere, yet data on the physical properties of snow and its effects on sea ice are limited. This lack of data leads to two significant problems: 1) significant biases in model representations of the sea ice cover and the processes that drive it, and 2) large uncertainties in how sea ice influences the global energy budget and the coupling of climate feedback. The  MOSAiC research initiative enabled the most extensive data collection of snow and surface scattering layer (SSL) properties over sea ice to date. During leg 5 of the MOSAiC expedition, we collected multi-scale (microscale to 100-m scale) measurements of the surface layer (snow/SSL) over first year ice (FYI) and MYI on a daily basis. The ultimate goal of our measurements is to determine the spatial distribution of physical properties of the surface layer. During leg 5 of the MOSAiC expedition, that surface layer changed from the  surface scattering layer (SSL),   characteristic for the melt season, to an early autumn snow pack. Here,  we will present data showing both a) the physical properties and the spatial distribution of the SSL during the late melt season and b) the transition of the sea ice surface from the SSL to the fresh autumn snowpack. The structural properties of this transition period are poorly documented, and this season is critical  for the initialization of sea ice and snow models. Furthermore, these data are crucial to interpret simultaneous observations of surface energy fluxes, surface optical and remote sensing data (microwave signals in particular), near-surface biochemical activity, and to understand the sea ice  processes that occur as the sea ice transitions from melting to freezing.</p>

scholarly journals Cryoconite hole connectivity on the Wright Lower Glacier, McMurdo Dry Valleys, Antarctica

2016 ◽  
Vol 62 (234) ◽  
pp. 714-724 ◽  
Author(s):  
SHELLEY MACDONELL ◽  
MARTIN SHARP ◽  
SEAN FITZSIMONS
Keyword(s):  
Spatial Variability ◽  
Drainage System ◽  
Chloride Content ◽  
Mcmurdo Dry Valleys ◽  
Hydrological Connectivity ◽  
Dry Valleys ◽  
Near Surface ◽  
Cryoconite Hole ◽  
Transfer Method ◽  
Surface Ice

ABSTRACTCryoconite holes can be important sources and stores of water and nutrients on cold and polythermal glaciers, and they provide a habitat for various forms of biota. Understanding the hydrological connectivity of cryoconite holes may be the key to understanding the transport of nutrients and biological material to the proglacial areas of such glaciers. This paper aims to characterize and explain spatial variability in the connectivity of ice-lidded cryoconite holes on a small, piedmont glacier in the McMurdo Dry Valleys through geochemical analysis of cryoconite hole waters. Solute concentrations in both surface and near-surface ice and cryoconite holes, vary greatly along the glacier centerline, and all sample types displayed similar spatial patterns of variability. Using chloride as a tracer, we estimated variations in cryoconite hole connectivity along the glacier centerline. We found that a previously used mass transfer method did not provide reliable estimates of the time period for which cryoconite hole waters had been isolated from the atmosphere. We attribute this to spatial variability in both the chloride content of the surface ice and surface ablation rates. The approach may, however, be used to qualitatively characterize spatial variations in the hydrological connectivity of the cryoconite holes. These results also suggest that ice-lidded cryoconite holes are never truly isolated from the near-surface drainage system.

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