02170nas a2200145 4500008004100000022001400041245013800055210006900193260001200262520161600274100002401890700002401914700002501938856006101963 2023 eng d a2169-900300aSpatial patterns of major ions and their relationship to sediment concentration in near surface glacier ice, Taylor Valley Antarctica0 aSpatial patterns of major ions and their relationship to sedimen c03/20243 a

Glaciers form the headwaters of many watersheds and, in arid polar environments, can provide the vast majority of water to downstream systems. Headwater watersheds are critically important for setting the chemistry for downstream systems, yet we know comparatively little about the patterns and processes that generate the geochemical signature of meltwater on glacier surfaces. Here, we focus on glaciers in the McMurdo Dry Valleys of Antarctica, the largest ice-free area on the continent, characterized by alpine glaciers flowing into broad, rocky valleys. We examine patterns from the coast inland, accumulation to ablation zones, laterally across individual glaciers, and through the zone of meltwater generation. We directly compare solute to sediment concentrations, a major source of dissolved solutes. Our findings agree with previous work that the overall meltwater chemistry of a given glacier is a product local sediment sources and of regional wind patterns: foehn winds moving from the ice sheet to the coast and on-shore sea breezes. Further, these patterns hold across an individual glacier. Finally, we find that the ice chemistry and sediment profiles reflect freeze-thaw and melt processes that occur at depth. This indicates that the transport and weathering of sediment in the ice profile likely has a strong influence on supra- and proglacial stream chemistry. This new understanding strengthens connections between physical and geochemical processes in cold-based polar glacier environments and helps us better understand the processes driving landscape and ecosystem connectivity.

1 aBergstrom, Anna, J.1 aWelch, Kathleen, A.1 aGooseff, Michael, N. uhttps://onlinelibrary.wiley.com/doi/10.1029/2022JF00698003417nas a2200193 4500008004100000245006200041210006200103260006200165490000800227520280000235653001503035653001903050653002103069653001203090100002203102700002603124700002503150856004803175 2021 eng d00aStream corridor connectivity controls on nitrogen cycling0 aStream corridor connectivity controls on nitrogen cycling aBoulder, CO, USAbUniversity of Colorado Boulderc05/20210 vPhD3 a

As water flows downstream, it is transported to and from environments that surround the visible stream. Along with surface water, these laterally and vertically connected environments comprise the stream corridor. Stream corridor connectivity influences many ecosystem services, including retention of excess nutrients. The subsurface area where stream water and groundwater mixes—the hyporheic zone—represents one of the most biogeochemically active parts of stream corridors.

The goal of my research is to advance understanding of how connectivity between different parts of a stream corridor controls the availability and retention of nitrogen (N), a nutrient that can limit primary productivity (low-N) and negatively impact water quality (excess N). First, I developed and applied a new machine learning method to objectively characterize the extent and variability of hyporheic exchange in terms of statistically unique functional zones using geophysical data. In applying this method to a benchmark dataset, I found that hyporheic extent does not scale uniformly with streamflow and that changes in the heterogeneity of connectivity differ over small (<10 m) distances. Next, I leveraged the relative simplicity of ephemeral streams of the McMurdo Dry Valleys (MDVs), Antarctica, to isolate stream corridor processes that influence the fate of N. Through intensive field sampling campaigns, I found that the hyporheic zone can be a persistent source of N even in this low nutrient environment. Next, I combined historic sample data and remote sensing analysis to estimate how much N is stored in an MDV stream corridor. My results indicate that up to 103 times more N is stored in this system than is exported each year, with most of this storage in the shallow (< 10 cm) hyporheic zone. Lastly, I examined 25 years of data for 10 streams to assess how stream corridor processes control concentration-discharge relationships. I found that in the absence of hillslope connectivity, stream corridor processes alone can maintain chemostasis – relatively small concentration changes with large fluctuations in streamflow – of both geogenic solutes and primary nutrients. My analysis also revealed that solutes subject to greater control by biological processes exhibit more variability within chemostatic relationships than weathering solutes that are only minimally influenced by biota.

Altogether, this research advances understanding of processes that are difficult to measure or are often overlooked in typical studies of temperate stream corridors. My findings provide insight into the surprising ways in which N is mobilized, transformed, and retained due to stream corridor connectivity in intermittent stream systems with few N inputs.

10aAntarctica10ahyporheic zone10anitrogen cycling10astreams1 aSingley, Joel, G.1 aHinckley, Eve-Lyn, S.1 aGooseff, Michael, N. uhttps://www.proquest.com/docview/257259312703158nas a2200181 4500008004100000245011200041210006900153260001200222300001200234490000700246520256300253100002402816700002502840700002002865700002102885700002202906856004802928 2020 eng d00aThe seasonal evolution of albedo across glaciers and the surrounding landscape of Taylor Valley, Antarctica0 aseasonal evolution of albedo across glaciers and the surrounding c03/2020 a769-7880 v143 a

The McMurdo Dry Valleys (MDVs) of Antarctica are a polar desert ecosystem consisting of alpine glaciers, ice-covered lakes, streams, and expanses of vegetation-free rocky soil. Because average summer temperatures are close to 0 ∘C, the MDV ecosystem in general, and glacier melt dynamics in particular, are both closely linked to the energy balance. A slight increase in incoming radiation or change in albedo can have large effects on the timing and volume of meltwater. However, the seasonal evolution or spatial variability of albedo in the valleys has yet to fully characterized. In this study, we aim to understand the drivers of landscape albedo change within and across seasons. To do so, a box with a camera, GPS, and shortwave radiometer was hung from a helicopter that flew transects four to five times a season along Taylor Valley. Measurements were repeated over three seasons. These data were coupled with incoming radiation measured at six meteorological stations distributed along the valley to calculate the distribution of albedo across individual glaciers, lakes, and soil surfaces. We hypothesized that albedo would decrease throughout the austral summer with ablation of snow patches and increasing sediment exposure on the glacier and lake surfaces. However, small snow events (<6 mm water equivalent) coupled with ice whitening caused spatial and temporal variability of albedo across the entire landscape. Glaciers frequently followed a pattern of increasing albedo with increasing elevation, as well as increasing albedo moving from east to west laterally across the ablation zone. We suggest that spatial patterns of albedo are a function of landscape morphology trapping snow and sediment, longitudinal gradients in snowfall magnitude, and wind-driven snow redistribution from east to west along the valley. We also compare our albedo measurements to the MODIS albedo product and found that overall the data have reasonable agreement. The mismatch in spatial scale between these two datasets results in variability, which is reduced after a snow event due to albedo following valley-scale gradients of snowfall magnitude. These findings highlight the importance of understanding the spatial and temporal variability in albedo and the close coupling of climate and landscape response. This new understanding of landscape albedo can constrain landscape energy budgets, better predict meltwater generation on from MDV glaciers, and how these ecosystems will respond to changing climate at the landscape scale.

1 aBergstrom, Anna, J.1 aGooseff, Michael, N.1 aMyers, Madeline1 aDoran, Peter, T.1 aCross, Julian, M. uhttps://www.the-cryosphere.net/14/769/2020/02240nas a2200145 4500008004100000245010800041210006900149260001200218490000800230520171900238100002101957700002501978700001702003856007402020 2018 eng d00aSoil Moisture Controls the Thermal Habitat of Active Layer Soils in the McMurdo Dry Valleys, Antarctica0 aSoil Moisture Controls the Thermal Habitat of Active Layer Soils c01/20180 v1233 a

Antarctic soil ecosystems are strongly controlled by abiotic habitat variables. Regional climate change in the McMurdo Dry Valleys is expected to cause warming over the next century, leading to an increase in frequency of freeze-thaw cycling in the soil habitat. Previous studies show that physiological stress associated with freeze-thaw cycling adversely affects invertebrate populations by decreasing abundance and positively selecting for larger body sizes. However, it remains unclear whether or not climate warming will indeed enhance the frequency of annual freeze-thaw cycling and associated physiological stresses. This research quantifies the frequency, rate, and spatial heterogeneity of active layer freezing to better understand how regional climate change may affect active layer soil thermodynamics, and, in turn, affect soil macroinvertebrate communities. Shallow active layer temperature, specific conductance, and soil moisture were observed along natural wetness gradients. Field observations show that the frequency and rate of freeze events are nonlinearly related to freezable soil moisture (θf). Over a 2 year period, soils at θf < 0.080 m3/m3 experienced between 15 and 35 freeze events and froze rapidly compared to soils with θf > 0.080 m3/m3, which experienced between 2 and 6 freeze events and froze more gradually. A numerical soil thermodynamic model is able to simulate observed freezing rates across a range of θf, reinforcing a well-known causal relationship between soil moisture and active layer freezing dynamics. Findings show that slight increases in soil moisture can potentially offset the effect of climate warming on exacerbating soil freeze-thaw cycling.

1 aWlostowski, Adam1 aGooseff, Michael, N.1 aAdams, Byron uhttps://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017JG00401801836nas a2200193 4500008004100000245013000041210006900171260001200240300001600252490000700268520116600275100002501441700002401466700002001490700002401510700002401534700001701558856006701575 2016 eng d00aStream biogeochemical and suspended sediment responses to permafrost degradation in stream banks in Taylor Valley, Antarctica0 aStream biogeochemical and suspended sediment responses to permaf c03/2016 a1723 - 17320 v133 a

 Stream channels in the McMurdo Dry Valleys are characteristically wide, incised, and stable. At typical flows, streams occupy a fraction of the oversized channels, providing habitat for algal mats. In January 2012, we discovered substantial channel erosion and subsurface thermomechanical erosion undercutting banks of the Crescent Stream. We sampled stream water along the impacted reach and compared concentrations of solutes to the long-term data from this stream ( ∼  20 years of monitoring). Thermokarst-impacted stream water demonstrated higher electrical conductivity, and concentrations of chloride, sulfate, sodium, and nitrate than the long-term medians. These results suggest that this mode of lateral permafrost degradation may substantially impact stream solute loads and potentially fertilize stream and lake ecosystems. The potential for sediment to scour or bury stream algal mats is yet to be determined, though it may offset impacts of associated increased nutrient loads to streams.

1 aGooseff, Michael, N.1 aVan Horn, David, J.1 aSudman, Zachary1 aMcKnight, Diane, M.1 aWelch, Kathleen, A.1 aLyons, Berry uhttp://www.biogeosciences.net/13/1723/2016/bg-13-1723-2016.pdf01763nas a2200157 4500008004100000245010800041210006900149260001200218300001200230490000700242520123700249100002101486700002501507700002501532856004801557 2015 eng d00aSpatiotemporal Dynamics of Wetted Soils across a Polar Desert Landscape, McMurdo Dry Valleys Antarctica0 aSpatiotemporal Dynamics of Wetted Soils across a Polar Desert La c04/2015 a197-2090 v273 aLiquid water is scarce across the landscape of the McMurdo Dry Valleys (MDV), Antarctica, a 3800 km2 ice-free region, and is chiefly associated with soils that are adjacent to streams and lakes (i.e. wetted margins) during the annual thaw season. However, isolated wetted soils have been observed at locations distal from water bodies. The source of water for the isolated patches of wet soil is potentially generated by a combination of infiltration from melting snowpacks, melting of pore ice at the ice table, and melting of buried segregation ice formed during winter freezing. High resolution remote sensing data gathered several times per summer in the MDV region were used to determine the spatial and temporal distribution of wet soils. The spatial consistency with which the wet soils occurred was assessed for the 2009–10 to 2011–12 summers. The remote sensing analyses reveal that cumulative area and number of wet soil patches varies among summers. The 2010–11 summer provided the most wetted soil area (10.21 km2) and 2009–10 covered the least (5.38 km2). These data suggest that wet soils are a significant component of the MDV cold desert land system and may become more prevalent as regional climate changes.1 aLangford, Z., L.1 aGooseff, Michael, N.1 aLampkin, Derrick, J. uhttp://dx.doi.org/10.1017/S095410201400060102505nas a2200193 4500008004100000245011800041210006900159260001200228300001400240490000700254520178100261100002402042700001502066700002402081700002502105700002202130700003302152856012602185 2014 eng d00aSoil microbial responses to increased moisture and organic resources along a salinity gradient in a polar desert.0 aSoil microbial responses to increased moisture and organic resou c05/2014 a3034-30430 v803 aMicrobial communities in extreme environments often have low diversity and specialized physiologies suggesting a limited resistance to change. The McMurdo Dry Valleys (MDV) are a microbially dominated, extreme ecosystem currently undergoing climate change-induced disturbances, including the melting of massive buried ice, cutting through of permafrost by streams, and warming events. These processes are increasing moisture across the landscape, altering conditions for soil communities by mobilizing nutrients and salts and stimulating autotrophic carbon inputs to soils. The goal of this study was to determine the effects of resource addition (water/organic matter) on the composition and function of microbial communities in the MDV along a natural salinity gradient representing an additional gradient of stress in an already extreme environment. Soil respiration and the activity of carbon-acquiring extracellular enzymes increased significantly (P < 0.05) with the addition of resources at the low- and moderate-salinity sites but not the high-salinity site. The bacterial community composition was altered, with an increase in Proteobacteria and Firmicutes with water and organic matter additions at the low- and moderate-salinity sites and a near dominance of Firmicutes at the high-salinity site. Principal coordinate analyses of all samples using a phylogenetically informed distance matrix (UniFrac) demonstrated discrete clustering among sites (analysis of similarity [ANOSIM], P < 0.05 and R > 0.40) and among most treatments within sites. The results from this experimental work suggest that microbial communities in this environment will undergo rapid change in response to the altered resources resulting from climate change impacts occurring in this region.1 aVan Horn, David, J.1 aOkie, J.G.1 aBuelow, Heather, N.1 aGooseff, Michael, N.1 aBarrett, John, E.1 aTakacs-Vesbach, Cristina, D. uhttps://mcm.lternet.edu/content/soil-microbial-responses-increased-moisture-and-organic-resources-along-salinity-gradient00637nas a2200169 4500008004100000245013500041210006900176260001200245300001400257490000600271100002100277700002500298700002500323700002200348700003300370856006400403 2013 eng d00aSeasonal controls on snow distribution and aerial ablation at the snow-patch and landscape scales, McMurdo Dry Valleys, Antarctica0 aSeasonal controls on snow distribution and aerial ablation at th c09/2013 a917 - 9310 v71 aEveland, Jeffery1 aGooseff, Michael, N.1 aLampkin, Derrick, J.1 aBarrett, John, E.1 aTakacs-Vesbach, Cristina, D. uhttp://www.the-cryosphere.net/7/917/2013/tc-7-917-2013.html00493nas a2200145 4500008004100000245007100041210006900112260001200181300001400193490000700207100002500214700002200239700002100261856006500282 2013 eng d00aShallow groundwater systems in a polar desert, McMurdo Dry Valleys0 aShallow groundwater systems in a polar desert McMurdo Dry Valley c02/2013 a171 - 1830 v211 aGooseff, Michael, N.1 aBarrett, John, E.1 aLevy, Joseph, S. uhttp://link.springer.com/article/10.1007%2Fs10040-012-0926-300619nas a2200169 4500008004100000245011800041210006900159260001200228300001600240490000700256100002100263700002500284700002500309700002200334700003300356856006000389 2013 eng d00aSpatial and temporal patterns of snow accumulation and aerial ablation across the McMurdo Dry Valleys, Antarctica0 aSpatial and temporal patterns of snow accumulation and aerial ab c09/2013 a2864 - 28750 v271 aEveland, Jeffery1 aGooseff, Michael, N.1 aLampkin, Derrick, J.1 aBarrett, John, E.1 aTakacs-Vesbach, Cristina, D. uhttp://onlinelibrary.wiley.com/doi/10.1002/hyp.9407/pdf03506nas a2200133 4500008004100000245006900041210006700110260004000177490000900217520305100226100002103277700002503298856004903323 2012 eng d00aSnow dynamics in a polar desert, McMurdo Dry Valleys, Antarctica0 aSnow dynamics in a polar desert McMurdo Dry Valleys Antarctica bPennsylvania State Universityc20120 vM.S.3 a

Snow in the McMurdo Dry Valleys is rare source of moisture for subnivian soils (beneath snow) in a cold desert ecosystem. While sublimation dominates the ablation process, measurable increases in soil moisture are expected to provide more favorable conditions for subnivian soil communities. In addition, snow cover insulates the underlying soil from temperature extremes. Quantifying the spatial distribution and ablation patterns of seasonal snow is necessary to understand these dynamics. Annual snowfall varies spatially ranging from 3 to 50 mm of snow water equivalent, with greater amounts occurring at the coast. Despite receiving very little precipitation, significant amounts of snow can accumulate (via aeolian redistribution) in topographic lees at the valley bottoms, forming thousands of discontinuous patches (typically 1-100 m2 in area). These patches have the potential to act as fertility islands, controlling the landscape distribution of microbial communities, and biogeochemical cycling.

High resolution imagery acquired during the 2009-2010 and 2010-2011 austral summers was used to quantify the distribution of snow across Taylor and Wright Valleys. An object-based classification was used to extract snow-covered area from the imagery. Coupled with topographic parameters, unique distribution patterns were characterized for 5 regions within the neighboring valleys. Time lapses of snow distribution during each season in each region provide insight into spatially characterizing the aerial ablation rates (change in area of landscape covered by snow) across the valleys. The distribution of snow-covered area during the 2009-2010 austral summer is used as a baseline for seasonal comparison. The surrounding regions of Lake Fryxell, Lake Hoare, Lake Bonney, Lake Brownworth, and Lake Vanda exhibited losses of snow-covered area of 9.61 km2 (-93%), 1.63 km2 (-72%), 1.07 km2 (-97%), 2.60 km2 (-82%), and 0.25 km2 (- 96%) respectively, as measured from peak accumulation in October to mid-January during the 2009-2010 season. Differences in aerial ablation rates within and across local regions suggest that both topographic variation and regional microclimates influence the ablation of seasonal snow cover. Elevation has shown to be the strongest control over aerial ablation. Fifteen 1 km2 plots (3 in each region) were selected to assess the prevalence of snow cover at smaller scales. Results confirm that snow patches form in the same locations each year with some minor deviations observed. Stable isotopes from snow patches also provide insights into temporal and spatial processes associated with ablation. At the snow patch scale, neighboring patches often exhibit considerable differences in aerial ablation rates, presumably controlled by snow depth. This highlights the importance of both the landscape and snow patch scales in assessing the effects of snow cover on biogeochemical cycling and microbial communities.

1 aEveland, Jeffery1 aGooseff, Michael, N. uhttps://etda.libraries.psu.edu/catalog/1268000685nas a2200193 4500008004100000245010500041210006900146260001200215300001400227490000700241100002400248700001700272700001900289700002900308700002500337700002400362700002100386856008400407 2010 eng d00aSpatial variations in the geochemistry of glacial meltwater streams in the Taylor Valley, Antarctica0 aSpatial variations in the geochemistry of glacial meltwater stre c12/2010 a662 - 6720 v221 aWelch, Kathleen, A.1 aLyons, Berry1 aWhisner, Carla1 aGardner, Christopher, B.1 aGooseff, Michael, N.1 aMcKnight, Diane, M.1 aPriscu, John, C. uhttp://www.montana.edu/lkbonney/DOCS/Publications/WelchEtAl2010Geochemistry.pdf00579nas a2200133 4500008004100000245011000041210006900151300001400220490000700234100002200241700002500263700003300288856012400321 2009 eng d00aSpatial variation in soil active-layer geochemistry across hydrologic margins in polar desert ecosystems.0 aSpatial variation in soil activelayer geochemistry across hydrol a2349-23580 v131 aBarrett, John, E.1 aGooseff, Michael, N.1 aTakacs-Vesbach, Cristina, D. uhttps://mcm.lternet.edu/content/spatial-variation-soil-active-layer-geochemistry-across-hydrologic-margins-polar-desert00592nas a2200121 4500008004100000245015900041210006900200260002900269490000900298100001300307700002500320856012500345 2007 eng d00aSpatial and Temporal Active Layer Thermal Dynamics from Temperature Time Series Analysis: Case Studies from Lake Fryxell, McMurdo Dry Valleys, Antarctica.0 aSpatial and Temporal Active Layer Thermal Dynamics from Temperat bColorado School of Mines0 vM.S.1 aIkard, S1 aGooseff, Michael, N. uhttps://mcm.lternet.edu/content/spatial-and-temporal-active-layer-thermal-dynamics-temperature-time-series-analysis-case00687nas a2200181 4500008004100000245010500041210006900146260001200215300001000227490000700237100002500244700001700269700002400286700002200310700002400332700002100356856012800377 2006 eng d00aA stable isotopic investigation of a polar desert hydrologic system, McMurdo Dry Valleys, Antarctica0 astable isotopic investigation of a polar desert hydrologic syste c02/2006 a60-710 v381 aGooseff, Michael, N.1 aLyons, Berry1 aMcKnight, Diane, M.1 aVaughn, Bruce, H.1 aFountain, Andrew, G1 aDowling, Carolyn uhttps://mcm.lternet.edu/content/stable-isotopic-investigation-polar-desert-hydrologic-system-mcmurdo-dry-valleys-antarctica00700nas a2200169 4500008004100000245014000041210006900181260001200250300001200262490000700274100002500281700002500306700002300331700002300354700002400377856012900401 2005 eng d00aSensitivity analysis of conservative and reactive stream transient storage models applied to field data from multiple-reach experiments0 aSensitivity analysis of conservative and reactive stream transie c05/2005 a479-4920 v281 aGooseff, Michael, N.1 aBencala, Kenneth, E.1 aScott, Durelle, T.1 aRunkel, Robert, L.1 aMcKnight, Diane, M. uhttps://mcm.lternet.edu/content/sensitivity-analysis-conservative-and-reactive-stream-transient-storage-models-applied-field00760nas a2200229 4500008004100000245012700041210006900168260001200237300001000249490000700259653001100266100002500277700002200302700002100324700002400345700001700369700002400386700001800410700002300428700002000451856005900471 2002 eng d00aSnow patch influence on soil biogeochemical processes and invertebrate distribution in the McMurdo Dry Valleys, Antarctica0 aSnow patch influence on soil biogeochemical processes and invert c02/2003 a91-990 v3510aBiggie1 aGooseff, Michael, N.1 aBarrett, John, E.1 aDoran, Peter, T.1 aFountain, Andrew, G1 aLyons, Berry1 aParsons, Andrew, N.1 aPorazinska, D1 aVirginia, Ross, A.1 aWall, Diana, H. uhttp://instaar.metapress.com/content/r086455ju7213711/