01525nas a2200145 4500008004100000245008300041210006900124260001200193490000800205520102800213100002201241700002101263700002101284856007401305 2019 eng d00aPrediction of ice-free conditions for a perennially ice-covered Antarctic lake0 aPrediction of icefree conditions for a perennially icecovered An c02/20190 v1243 a

Although perennially ice-covered Antarctic lakes have experienced variable ice thicknesses over the past several decades, future ice thickness trends and associated aquatic biological responses under projected global warming remain unknown. Heat stored in the water column in chemically stratified Antarctic lakes that have mid-depth temperature maxima, can significantly influence the ice thickness trends via upward heat flux to the ice/water interface. We modeled ice thickness of the west of lobe of Lake Bonney, Antarctica based on possible future climate scenarios utilizing a 1D thermodynamic model that accounts for surface radiative fluxes as well as the heat flux associated with the temperature evolution of the water column. Model results predict that the ice cover of Lake Bonney will shift from perennial to seasonal within one to four decades, a change that will drastically influence ecosystem processes within the lake.

1 aObryk, Maciek, K.1 aDoran, Peter, T.1 aPriscu, John, C. uhttps://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JF00475601630nas a2200169 4500008004100000245008200041210006900123260001200192490000600204520109200210100002201302700002401324700002101348700001701369700001601386856005801402 2018 eng d00aDrivers of solar radiation variability in the McMurdo Dry Valleys, Antarctica0 aDrivers of solar radiation variability in the McMurdo Dry Valley c03/20180 v83 a

 

Annually averaged solar radiation in the McMurdo Dry Valleys, Antarctica has varied by over 20 W m−2 during the past three decades; however, the drivers of this variability are unknown. Because small differences in radiation are important to water availability and ecosystem functioning in polar deserts, determining the causes are important to predictions of future desert processes. We examine the potential drivers of solar variability and systematically eliminate all but stratospheric sulfur dioxide. We argue that increases in stratospheric sulfur dioxide increase stratospheric aerosol optical depth and decrease solar intensity. Because of the polar location of the McMurdo Dry Valleys (77–78°S) and relatively long solar ray path through the stratosphere, terrestrial solar intensity is sensitive to small differences in stratospheric transmissivity. Important sources of sulfur dioxide include natural (wildfires and volcanic eruptions) and anthropogenic emission.

 

1 aObryk, Maciek, K.1 aFountain, Andrew, G1 aDoran, Peter, T.1 aLyons, Berry1 aEastman, R. uhttp://www.nature.com/articles/s41598-018-23390-7.pdf02508nas a2200181 4500008004100000245017000041210006900211260001200280300001600292490000700308520183400315100002302149700002102172700002202193700002302215700002102238856006702259 2018 eng d00aThe physical limnology of a permanently ice-covered and chemically stratified Antarctic lake using high resolution spatial data from an autonomous underwater vehicle0 aphysical limnology of a permanently icecovered and chemically st c05/2018 a1234 - 12520 v633 a

We used an Environmentally Non-Disturbing Under-ice Robotic ANtarctic Explorer to make measurements of conductivity and temperature in Lake Bonney, a chemically stratified, permanently ice-covered Antarctic lake that abuts Taylor Glacier, an outlet glacier from the Polar Plateau. The lake is divided into two lobes – East Lobe Bonney (ELB) and West Lobe Bonney (WLB), each with unique temperature and salinity profiles. Most of our data were collected in November 2009 from WLB to examine the influence of the Taylor Glacier on the structure of the water column. Temperatures adjacent to the glacier face between 20 m and 22 m were 38C colder than in the rest of WLB, due to latent heat transfer associated with melting of the submerged glacier face and inflow of cold brines that originate beneath the glacier. Melting of the glacier face into the salinity gradient below the chemocline generates a series of nearly horizontal intrusions into WLB that were previously documented in profiles measured with 3 cm vertical resolution in 1990–1991. WLB and ELB are connected by a narrow channel through which water can be exchanged over a shallow sill that controls the position of the chemocline in WLB. A complex exchange flow appears to exist through the narrows, driven by horizontal density gradients and melting at the glacier face. Superimposed on the exchange is a net west- to-east flow generated by the higher volume of meltwater inflows to WLB. Both of these processes can be expected to be enhanced in the future as more meltwater is produced. 

1 aSpigel, Robert, H.1 aPriscu, John, C.1 aObryk, Maciek, K.1 aStone, William, C.1 aDoran, Peter, T. uhttp://onlinelibrary.wiley.com/wol1/doi/10.1002/lno.10768/full01634nas a2200217 4500008004100000245010200041210006900143260001200212300001400224490000600238520092200244100002401166700002901190700002201219700002101241700002501262700002401287700001301311700002101324856007101345 2017 eng d00aHigh-resolution elevation mapping of the McMurdo Dry Valleys, Antarctica, and surrounding regions0 aHighresolution elevation mapping of the McMurdo Dry Valleys Anta c07/2017 a435 - 4430 v93 a

We present detailed surface elevation measurements for the McMurdo Dry Valleys, Antarctica derived from aerial lidar surveys flown in the austral summer of 2014–2015 as part of an effort to understand geomorphic changes over the past decade. Lidar return density varied from 2 to > 10 returns  m−2 with an average of about 5  returns  m−2. Vertical and horizontal accuracies are estimated to be 7 and 3 cm, respectively. In addition to our intended targets, other ad hoc regions were also surveyed including the Pegasus flight facility and two regions on Ross Island, McMurdo Station, Scott Base (and surroundings), and the coastal margin between Cape Royds and Cape Evans. These data are included in this report and data release. The combined data are freely available at https://doi.org/10.5069/G9D50JX3.

1 aFountain, Andrew, G1 aFernandez-Diaz, Juan, C.1 aObryk, Maciek, K.1 aLevy, Joseph, S.1 aGooseff, Michael, N.1 aVan Horn, David, J.1 aMorin, P1 aShrestha, Ramesh uhttps://www.earth-syst-sci-data.net/9/435/2017/essd-9-435-2017.pdf02255nas a2200193 4500008004100000245007900041210006900120260001200189300001400201490000800215520163600223100002001859700002501879700002401904700002101928700002201949700002401971856006601995 2017 eng d00aImpacts of permafrost degradation on a stream in Taylor Valley, Antarctica0 aImpacts of permafrost degradation on a stream in Taylor Valley A c05/2017 a205 - 2130 v2853 a

The McMurdo Dry Valleys (MDV) of Antarctica are an ice-free landscape that supports a complex, microbially dominated ecosystem despite a severely arid, cold environment (b 5 cm water equivalent/y, − 18 °C mean annual air temperature). Recent observations of permafrost degradation in the coastal zones of the MDV suggest that this region is nearing a threshold of rapid landscape change. In 2012, substantial thermokarst development was observed along several kilometers of the west branch of Crescent Stream in Taylor Valley mostly in the form of bank failures, whereas the adjacent east branch was unaffected. The objective of this study was to quantify the changes to the stream banks of the west branch of Crescent Stream and to determine the impacts on the composition of the stream bed material. Three annually repeated terrestrial LiDAR scans were compared to determine the rates of ground surface change caused by thermokarst formation on the stream bank. The areal extent of the thermokarst was shown to be decreasing; however, the average vertical rate of retreat remained constant. Field measurements of bed materials indicated that the west branch and the reach downstream of the confluence (of east and west branches) consistently contained more fines than the unaffected east branch. This suggests that the finer bed material is a result of the thermokarst development on the west branch. These finer bed material compositions are likely to increase the mobility of the bed material, which will have implications for stream morphology, stream algal mat communities, and downstream aquatic ecosystems.

1 aSudman, Zachary1 aGooseff, Michael, N.1 aFountain, Andrew, G1 aLevy, Joseph, S.1 aObryk, Maciek, K.1 aVan Horn, David, J. uhttp://linkinghub.elsevier.com/retrieve/pii/S0169555X1630846700637nas a2200157 4500008004100000245015300041210007000194260001200264300001200276490000700288100002200295700002100317700002100338700002700359856009300386 2017 eng d00aThe influence of föhn winds on Glacial Lake Washburn and palaeotemperatures in the McMurdo Dry Valleys, Antarctica, during the Last Glacial Maximum0 ainfluence of föhn winds on Glacial Lake Washburn and palaeotempe c10/2017 a457-4670 v291 aObryk, Maciek, K.1 aDoran, Peter, T.1 aWaddington, E.D.1 aMcKay, Christopher, P. uhttps://www.cambridge.org/core/product/identifier/S0954102017000062/type/journal_article02953nas a2200169 4500008004100000245010500041210006900146260001200215300001400227490000700241520241100248100001502659700002302674700002202697700002102719856004302740 2016 eng d00aGrowth dynamics of a laminated microbial mat in response to variable irradiance in an Antarctic lake0 aGrowth dynamics of a laminated microbial mat in response to vari c02/2016 a396 - 4100 v613 a
  1. Laminated microbial mats are important ecosystem components of perennially ice-covered Antarctic dry valley lakes. In order to understand better their response to changing environment, we made observations and carried out a manipulation experiment to determine their response to variations in irradiance in Lake Hoare (77°38′ S, 162°53′ E).
  2. Ice transparency was the most variable parameter that affected benthic light dose, both spatially and between years. Patterns of lamina accrual corresponded to irradiance history, with laminae that were initiated in high transmission years thicker than those from low transmission years.
  3. A shading experiment confirmed that accrual of lamina thickness, calcite precipitation and ash-free dry mass were determined by irradiance, but photosynthetic biomass and phototrophic species composition were less affected.
  4. Buried laminae decomposed only slowly over time, with potentially viable phototrophs many laminae down into the microbial mat. Decay rate increased only slightly with shading.
  5. We conclude that the microbial mats in Lake Hoare are characterised by remarkable stability, with slow accumulation rates and turnover of biomass over time. Photosynthetic biomass and species composition appeared to be stable across long time periods, with interannual variation in lamination pattern due to differential accumulation of extracellular polysaccharide and representing the visible expression of annual growth conditions.
1 aHawes, Ian1 aJungblut, Anne, D.1 aObryk, Maciek, K.1 aDoran, Peter, T. uhttp://doi.wiley.com/10.1111/fwb.1271500649nas a2200169 4500008004100000022001400041245017800055210006900233260001200302300001600314490000700330100002200337700002300359700002200382700002100404856005400425 2016 eng d a0016-803300aHigh-resolution ground-penetrating radar profiles of perennial lake ice in the McMurdo Dry Valleys, Antarctica: Horizon attributes, unconformities, and subbottom penetration0 aHighresolution groundpenetrating radar profiles of perennial lak c01/2016 aWA13 - WA200 v811 aDugan, Hilary, A.1 aArcone, Steven, A.1 aObryk, Maciek, K.1 aDoran, Peter, T. uhttp://library.seg.org/doi/10.1190/geo2015-0159.101797nas a2200253 4500008004100000022001400041245007900055210006900134260001200203300001400215490000700229520101000236100002401246700001601270700001701286700002101303700002001324700002501344700002201369700002101391700002801412700002301440856008001463 2016 eng d a0006-356800aThe Impact of a Large-Scale Climate Event on Antarctic Ecosystem Processes0 aImpact of a LargeScale Climate Event on Antarctic Ecosystem Proc c10/2016 a848 - 8630 v663 a

Extreme climate and weather events, such as a drought, hurricanes, or ice storms, can strongly imprint ecosystem processing and may alter ecosystem structure. Ecosystems in extreme environments are particularly vulnerable because of their adaptation to severe limitations in energy, water, or nutrients. The vulnerability can be expressed as a relatively long-lasting ecosystem response to a small or brief change in environmental conditions. Such an event occurred in Antarctica and affected two vastly different ecosystems: a marine-dominated coastal system and a terrestrial polar desert. Both sites experienced winds that warmed air temperatures above the 0°C threshold, resulting in extensive snow and ice melt and triggering a series of cascading effects through the ecosystems that are continuing to play out more than a decade later. This highlights the sensitivity of Antarctic ecosystems to warming events, which should occur more frequently in the future with global climate warming.

1 aFountain, Andrew, G1 aSaba, Grace1 aAdams, Byron1 aDoran, Peter, T.1 aFraser, William1 aGooseff, Michael, N.1 aObryk, Maciek, K.1 aPriscu, John, C.1 aStammerjohn, Sharon, E.1 aVirginia, Ross, A. uhttp://academic.oup.com/bioscience/article-pdf/66/10/848/7510601/biw110.pdf02462nas a2200193 4500008004100000022001300041245008800054210006900142260001600211300001400227490000800241520184200249100002102091700002202112700002302134700002502157700001502182856007102197 2016 eng d a0921818100aLake Vanda: A sentinel for climate change in the McMurdo Sound Region of Antarctica0 aLake Vanda A sentinel for climate change in the McMurdo Sound Re cJan-09-2016 a213 - 2270 v1443 a

Lake Vanda is a perennially ice-covered, meromictic, endorheic lake located in the McMurdo Dry Valleys of Antarctica, and an exceptional sentinel of climate change within the region. Lake levels rose 15 m over the past 68 years in response to climate-driven variability in ice-cover sublimation, meltwater production, and annual discharge of the Onyx River, the main source of water to the lake. Evidence from a new bathymetric map and water balance model combined with annual growth laminations in benthic mats suggest that the most recent filling trend began abruptly 80 years ago, in the early 1930s. This change increased lake volume by > 50%, triggered the formation of a new, upper, thermohaline convection cell, and cooled the lower convection cell by at least 2 °C and the bottom-most waters by at > 4 °C. Additionally, the depth of the deep chlorophyll a maximum rose by > 2 m, and deep-growing benthic algal mats declined while shallow benthic mats colonized freshly inundated areas. We attribute changes in hydrology to regional variations in air flow related to the strength and position of the Amundsen Sea Low (ASL) pressure system which have increased the frequency of down-valley, föhn winds associated with surface air temperature warming in the McMurdo Dry Valleys. The ASL has also been implicated in the recent warming of the Antarctic Peninsula, and provides a common link for climate-related change on opposite sides of the continent. If this trend persists, Lake Vanda should continue to rise and cool over the next 200 years until a new equilibrium lake level is achieved. Most likely, future lake rise will lead to isothermal conditions not conducive to thermohaline convection, resulting in a drastically different physical, biogeochemical, and biological structure than observed today.

1 aCastendyk, Devin1 aObryk, Maciek, K.1 aLeidman, Sasha, Z.1 aGooseff, Michael, N.1 aHawes, Ian uhttp://www.sciencedirect.com/science/article/pii/S092181811530014X02208nas a2200181 4500008004100000022001400041245010400055210006900159260001200228300001100240520160100251100002201852700002101874700001801895700002701913700002101940856006501961 2016 eng d a0022-143000aModeling the thickness of perennial ice covers on stratified lakes of the Taylor Valley, Antarctica0 aModeling the thickness of perennial ice covers on stratified lak c06/2016 a1 - 103 a
A 1-D ice cover model was developed to predict and constrain drivers of long-term ice thickness trends in chemically stratified lakes of Taylor Valley, Antarctica. The model is driven by surface radiative heat fluxes and heat fluxes from the underlying water column. The model successfully reproduced 16 a (between 1996 and 2012) of ice thickness changes for the west lobe of Lake Bonney (average ice thickness = 3.53 m) and Lake Fryxell (average ice thickness = 4.22 m). Long-term ice thickness trends require coupling with the thermal structure of the water column. The heat stored within the temperature maximum of lakes exceeding a liquid water column depth of 20 m can either impede or facilitate ice thickness change depending on the predominant climatic trend (cooling or warming). As such, shallow (<20 m deep water columns) perennially ice-covered lakes without deep temperature maxima are more sensitive indicators of climate change. The long-term ice thickness trends are a result of surface energy flux and heat flux from the deep temperature maximum in the water column, the latter of which results from absorbed solar radiation.

 

1 aObryk, Maciek, K.1 aDoran, Peter, T.1 aHicks, J., A.1 aMcKay, Christopher, P.1 aPriscu, John, C. uhttp://www.journals.cambridge.org/abstract_S002214301600069100943nas a2200253 4500008004100000022001400041245008700055210006900142260001600211300001400227490000700241100002200248700002100270700002600291700002500317700001200342700002900354700002100383700002100404700002800425700002700453700002200480856018700502 2016 eng d a0006-356800aResponses of Antarctic Marine and Freshwater Ecosystems to Changing Ice Conditions0 aResponses of Antarctic Marine and Freshwater Ecosystems to Chang cJan-10-2016 a864 - 8790 v661 aObryk, Maciek, K.1 aDoran, Peter, T.1 aFriedlaender, Ari, S.1 aGooseff, Michael, N.1 aLi, Wei1 aMorgan-Kiss, Rachael, M.1 aPriscu, John, C.1 aSchofield, Oscar1 aStammerjohn, Sharon, E.1 aSteinberg, Deborah, K.1 aDucklow, Hugh, W. uhttps://academic.oup.com/bioscience/article-lookup/doi/10.1093/biosci/biw109https://academic.oup.com/bioscience/article/66/10/864/2415532/Responses-of-Antarctic-Marine-and-Freshwater02038nas a2200181 4500008004100000022001400041245011000055210006900165260001200234300000900246490001400255520146300269100001801732700001501750700002201765700002101787856004801808 2015 eng d a1365-207900aSediment transport dynamics on an ice-covered lake: The “floating” boulders of Lake Hoare, Antarctica0 aSediment transport dynamics on an icecovered lake The floating b c04/2015 a1-120 vfirstview3 a

Between 1995 and 2011 a global positioning system survey of 13 boulders and three ablation stakes (long stakes frozen in the ice) on the frozen surface of Lake Hoare was undertaken. Data interpretation illustrates complexities of post-depositional transport dynamics of boulders. Earlier studies on comparable datasets have suggested linear ‘conveyor’ type transport mechanisms for lake surface boulders. Yet explanations for non-linear boulder displacements or ‘walks’ and the mechanisms responsible for movements are inadequate. Two modes of boulder specific movement were observed. First, localized changes in the ice surface promote individual boulder movement (rolling). Second, ice rafting, which indicates the displacement of ‘plates’ of lake ice on which the boulder is located. Ablation stakes used as fixed survey control points support the hypothesis that ice cover moves as discrete plates rather than as a single homogenous mass. Factors that create the conditions to generate either of the two modes of movement may be related to location specific energy budgets. A relationship between average orientations and prevailing wind direction was also observed. The investigation describes the local-scale behaviour of surveyed boulders, and offers methodologies and interpretive frameworks for additional studies of modern and ancient sediment transportation dynamics in Antarctic lacustrine environments.

1 aAllen, P., P.1 aHewitt, R.1 aObryk, Maciek, K.1 aDoran, Peter, T. uhttp://dx.doi.org/10.1017/S095410201400055802874nas a2200133 4500008004100000245008500041210006900126260004000195490001000235520241400245100002202659700002102681856003802702 2014 eng d00aHydrological and Biogeochemical Modeling of Taylor Valley Lakes, East Antarctica0 aHydrological and Biogeochemical Modeling of Taylor Valley Lakes  aChicago, ILbUniversity of Illinois0 vPh.D.3 a

Taylor Valley, McMurdo Dry Valleys, East Antarctica contains three perennially ice-covered lakes located in closed basins. The lakes respond to climatic changes on seasonal and decadal scales due to their existence on a very narrow climatic spectrum. The climate has to be sufficiently warm during the austral summer to induce glacial melt yet cold enough to maintain the ice covers year round. This thesis is focused on better understanding and constraining the sensitivity of past and present lakes to changes in climatic forcings. Melt water generation for large proglacial lakes, that existed during the Last Glacial Maximum, is attributed to strong westerly winds that increase surface air temperature above freezing, prolonging the melt season. The high frequency of westerly winds during the Last Glacial Maximum, based on the ice core record from Taylor Dome, is responsible for generation of enough glacial melt to sustain large proglacial lakes during this time period, suggesting that summer surface air temperatures were as warm as present day. Contemporary lakes are much smaller, however, the effect of strong westerly winds on modern lakes is equally profound. Strong winds are responsible for aeolian sediment deposition on the surface of the ice covers. The deposited sediment, on the other hand, absorbs more solar radiation and preferentially decreases the ice thickness around it. The localized ice thinning allows a greater amount of light penetration into the water column, which is negatively correlated with chlorophyll-a concentration. This negative correlation does not indicate changes in biomass; rather, it is a result of the short-term photo-adaptation of phytoplankton to the light intensity by increasing/decreasing light harvesting antenna size. The ice thicknesses in Taylor Valley lakes have been fluctuating since the first measurements were obtained. A one-dimensional physics-based ice thickness model was developed capable of reproducing 16 years of ice thickness trends for two different lakes. The model is based on surface radiative fluxes while considering heat fluxes from the water column. Deep lakes with well-developed temperature maximum can facilitate or hinder ice thickness growth/decay due to the heat flux from the underlying water column. This finding suggests that not all perennially ice-covered lakes can be used as a proxy for climatic changes.

1 aObryk, Maciek, K.1 aDoran, Peter, T. uhttp://hdl.handle.net/10027/1890903712nas a2200157 4500008004100000245021300041210006900254260001200323300001600335490000800351520308500359100002203444700002103466700002103487856004603508 2014 eng d00aThe permanent ice cover of Lake Bonney, Antarctica: The influence of thickness and sediment distribution on photosynthetically available radiation and chlorophyll-a distribution in the underlying water column0 apermanent ice cover of Lake Bonney Antarctica The influence of t c09/2014 a1879 - 18910 v1193 a

The thick permanent ice cover on the lakes of the McMurdo Dry Valleys, Antarctica, inhibits spatial lake sampling due to logistical constraints of penetrating the ice cover. To date most sampling of these lakes has been made at only a few sites with the assumption that there is a spatial homogeneity of the physical and biogeochemical properties of the ice cover and the water column at any given depth. To test this underlying assumption, an autonomous underwater vehicle (AUV) was deployed in Lake Bonney, Taylor Valley. Measurements were obtained over the course of 2 years in a 100 × 100 m horizontal sampling grid (at a 0.2 m vertical resolution). Additionally, the AUV measured the ice thickness (in water equivalent) and collected images looking up through the ice, which were used to quantify sediment distribution on the surface and within the ice. Satellite imagery was used to map sediment distribution on the surface of the ice. We present results of the spatial investigation of the sediment distribution on the ice cover and its effects on biological processes, with particular emphasis on photosynthetically active radiation (PAR). The surface sediment is a secondary controller of the ice cover thickness, which in turn controls the depth-integrated PAR in the water column. Our data revealed that depth-integrated PAR was negatively correlated with depth-integrated chlorophyll-a (r = 0.88, p < 0.001, n = 83), which appears to be related to short-term photoadaptation of phytoplanktonic communities to spatial and temporal variation in PAR within the water column.

1 aObryk, Maciek, K.1 aDoran, Peter, T.1 aPriscu, John, C. uhttp://doi.wiley.com/10.1002/2014JG00267200501nas a2200133 4500008004100000245007300041210006900114260001200183490000700195100002200202700002200224700002100246856010000267 2013 eng d00aLake ice ablation rates from permanently ice-covered Antarctic lakes0 aLake ice ablation rates from permanently icecovered Antarctic la c01/20130 v591 aDugan, Hilary, A.1 aObryk, Maciek, K.1 aDoran, Peter, T. uhttps://mcm.lternet.edu/content/lake-ice-ablation-rates-permanently-ice-covered-antarctic-lakes