scholarly journals Antarctic Permafrost Degassing Revealed By Extensive Soil Gas and Co2 Flux Survey in Taylor Valley

2021 ◽  
Author(s):  
Livio Ruggiero ◽  
Alessandra Sciarra ◽  
Adriano Mazzini ◽  
Fabio Florindo ◽  
Gary Wilson ◽  
...  
Keyword(s):  
Austral Summer ◽  
Soil Surface ◽  
Co2 Flux ◽  
Permafrost Degradation ◽  
Dry Valleys ◽  
Climate Conditions ◽  
Taylor Valley ◽  
C Cycle ◽  
High Concentrations ◽  
Soil Gases

Abstract McMurdo Dry Valleys comprise 10% of the ice-free soil surface areas in Antarctica. Permafrost stability plays an important role in C-cycle as it potentially stores considerable quantities of greenhouse gases. While the geomorphology of the Dry Valleys reflects a long history of changing climate conditions, comparison with the rapidly warming Northern polar region suggests that future climate and ecosystems may change more rapidly from permafrost degradation. In Austral summer 2019/2020 a comprehensive sampling of soil gases and CO2 flux measurements was undertaken in the Taylor Valley, with the aims to identify potential presence of soil gases in the active layer. The results obtained show high concentrations of CH4, CO2, He and an increasing CO2 flux rate. We identify the likely source of the gas to be from dissolved gases in deep brine moving from inland (potentially underneath the Antarctic Ice Sheet) to the coast at depth beneath the permafrost layer.

scholarly journals Soil surface CO<sub>2</sub> flux increases with successional time in a fire scar chronosequence of Canadian boreal jack pine forest

2010 ◽  
Vol 7 (5) ◽  
pp. 1375-1381 ◽  
Author(s):  
D. R. Smith ◽  
J. D. Kaduk ◽  
H. Balzter ◽  
M. J. Wooster ◽  
G. N. Mottram ◽  
...  
Keyword(s):  
Forest Fires ◽  
Soil Surface ◽  
Co2 Flux ◽  
Jack Pine ◽  
Future Research ◽  
Fire Scars ◽  
Fire Scar ◽  
C Cycle ◽  
Meta Analyses ◽  
In Fire

Abstract. To fully understand the carbon (C) cycle impacts of forest fires, both C emissions during the fire and post-disturbance fluxes need to be considered. The latter are dominated by soil surface CO2 flux (Fs), which is still subject to large uncertainties. Fire is generally regarded as the most important factor influencing succession in the boreal forest biome and fire dependant species such as jack pine are widespread. In May 2007, we took concurrent Fs and soil temperature (Ts) measurements in boreal jack pine fire scars aged between 0 and 59 years since fire. To allow comparisons between scars, we adjusted Fs for Ts (FsT) using a Q10 of 2. Mean FsT ranged from 0.56 (± 0.30 sd) to 1.94 (± 0.74 sd) μmol CO2 m−2 s−1. Our results indicate a difference in mean FsT between recently burned (4 to 8 days post fire) and non-burned mature (59 years since fire) forest (P < 0.001), though no difference was detected between recently burned (4 to 8 days post fire) and non-burned young (16 years since fire) forest (P = 0.785). There was a difference in mean FsT between previously young (16 years since fire) and intermediate aged (32 years since fire) scars that were both subject to fire in 2007 (P < 0.001). However, there was no difference in mean FsT between mature (59 years since fire) and intermediate aged (32 years since fire) scars that were both subjected to fire in 2007 (P = 0.226). Furthermore, there was no difference in mean FsT between mature (59 years since fire) and young scars (16 years since fire) that were both subjected to fire in 2007 (P = 0.186). There was an increase in FsT with time since fire for the chronosequence 0, 16 and 59 years post fire (P < 0.001). Our results lead us to hypothesise that the autotrophic:heterotrophic soil respiration ratio increases over post-fire successional time in boreal jack pine systems, though this should be explored in future research. The results of this study contribute to a better quantitative understanding of Fs in boreal jack pine fire scars and will facilitate meta-analyses of Fs in fire scar chronosequences.

scholarly journals The impact of fossil fuel burning related to scientific activities in the McMurdo Dry Valleys, Antarctica: Revisited

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
W. Berry Lyons ◽  
Elsa Saelens ◽  
Kathleen A. Welch
Keyword(s):  
Fossil Fuel ◽  
Austral Summer ◽  
Dry Valleys ◽  
Carbon And Nitrogen ◽  
Fossil Fuel Burning ◽  
Taylor Valley ◽  
Fuel Burning ◽  
Field Season ◽  
C And N ◽  
The Impact

Fossil fuel use associated with scientific activities in the Taylor Valley, Antarctic has been examined to determine the fluxes of particulate organic and elemental carbon and nitrogen as well as NOx for the 2015–2016 austral summer field season. These carbon and nitrogen fluxes are compared to our previously published calculations for the 1997–1998 austral summer. In addition, we compile fossil fuel usage and resulting C and N fluxes from the major field camp in Taylor Valley, Lake Hoare Camp (LHC) from the late 1990’s through 2017. In general, the annual fluxes do vary from year to year, but there is no significant trend, at least during the primary summer field season. There is indication that increasing the length of scientific operations does increase the C and N inputs via fossil fuel burning. This works supports our original results demonstrating that over long periods of time the anthropogenic flux of N from local fossil fuel burning could become quantitatively important in the region. Although the particulate C fluxes remain very low, the recent finding of black carbon in the Taylor Valley landscape indicates more on-going monitoring of the source of this material is merited.

scholarly journals The seasonal evolution of albedo across glaciers and the surrounding landscape of Taylor Valley, Antarctica

2020 ◽  
Vol 14 (3) ◽  
pp. 769-788 ◽  
Author(s):  
Anna Bergstrom ◽  
Michael N. Gooseff ◽  
Madeline Myers ◽  
Peter T. Doran ◽  
Julian M. Cross
Keyword(s):  
Temporal Variability ◽  
Austral Summer ◽  
Desert Ecosystem ◽  
Energy Budgets ◽  
Spatial And Temporal Variability ◽  
Dry Valleys ◽  
Seasonal Evolution ◽  
Taylor Valley ◽  
Incoming Radiation ◽  
Longitudinal Gradients

Abstract. 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.

scholarly journals The seasonal evolution of albedo across glaciers and the surrounding landscape of the Taylor Valley, Antarctica

2019 ◽  
Author(s):  
Anna Bergstrom ◽  
Michael Gooseff ◽  
Madeline Myers ◽  
Peter T. Doran
Keyword(s):  
Austral Summer ◽  
Short Wave ◽  
Desert Ecosystem ◽  
Dry Valleys ◽  
Seasonal Evolution ◽  
Taylor Valley ◽  
Incoming Radiation ◽  
Dry Valley ◽  
Summer Temperatures ◽  
Surrounding Landscape

Abstract. 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, glacier melt dynamics in particular, but the Dry Valley ecosystem in general, are 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 melt water. However, we have yet to fully characterize the seasonal evolution or spatial variability of albedo in the valleys. In this study, we aim to understand the drivers of landscape albedo change within and across seasons. To do so, we used a camera, gps, and short wave radiometer from a helicopter-based platform to fly transects 4–5 times a season along Taylor Valley over three seasons. We coupled these data with incoming radiation measured at 6 meteorological stations distributed along the valley to calculate the distribution of albedo across individual glaciers, lakes, and the soil surfaces. We hypothesized that albedo would decrease throughout the austral summer with ablation of snow patches and ice and increasing sediment exposure on the glacier and lake surfaces. However, small snow events (

scholarly journals Dissolved organic nutrients at the interface of fresh and marine waters: flow regime changes, biogeochemical cascades and picocyanobacterial blooms—the example of Florida Bay, USA

2021 ◽  
Author(s):  
Patricia M. Glibert ◽  
Cynthia A. Heil ◽  
Christopher J. Madden ◽  
Stephen P. Kelly
Keyword(s):  
Water Quality ◽  
Anthropogenic Activities ◽  
Florida Bay ◽  
Climate Conditions ◽  
Regime Changes ◽  
Physico Chemical ◽  
Organic Nutrients ◽  
High Concentrations ◽  
Chemical Conditions ◽  
Favorable Conditions

AbstractThe availability of dissolved inorganic and organic nutrients and their transformations along the fresh to marine continuum are being modified by various natural and anthropogenic activities and climate-related changes. Subtropical central and eastern Florida Bay, located at the southern end of the Florida peninsula, is classically considered to have inorganic nutrient conditions that are in higher-than-Redfield ratio proportions, and high levels of organic and chemically-reduced forms of nitrogen. However, salinity, pH and nutrients, both organic and inorganic, change with changes in freshwater flows to the bay. Here, using a time series of water quality and physico-chemical conditions from 2009 to 2019, the impacts of distinct changes in managed flow, drought, El Niño-related increases in precipitation, and intensive storms and hurricanes are explored with respect to changes in water quality and resulting ecosystem effects, with a focus on understanding why picocyanobacterial blooms formed when they did. Drought produced hyper-salinity conditions that were associated with a seagrass die-off. Years later, increases in precipitation resulting from intensive storms and a hurricane were associated with high loads of organic nutrients, and declines in pH, likely due to high organic acid input and decaying organic matter, collectively leading to physiologically favorable conditions for growth of the picocyanobacterium, Synechococcus spp. These conditions, including very high concentrations of NH4+, were likely inhibiting for seagrass recovery and for growth of competing phytoplankton or their grazers. Given projected future climate conditions, and anticipated cycles of drought and intensive storms, the likelihood of future seagrass die-offs and picocyanobacterial blooms is high.

Climate Conditions at Perennially Ice-Covered Lake Untersee, East Antarctica

2015 ◽  
Vol 54 (7) ◽  
pp. 1393-1412 ◽  
Author(s):  
Dale T. Andersen ◽  
Christopher P. McKay ◽  
Victor Lagun
Keyword(s):  
Wind Speed ◽  
Austral Summer ◽  
Solar Flux ◽  
East Antarctica ◽  
Daily Maximum ◽  
Mean Annual Temperature ◽  
Secondary Source ◽  
Climate Conditions ◽  
Wind Speeds ◽  
Strong Winds

AbstractIn November 2008 an automated meteorological station was established at Lake Untersee in East Antarctica, producing a 5-yr data record of meteorological conditions at the lake. This dataset includes five austral summer seasons composed of December, January, and February (DJF). The average solar flux at Lake Untersee for the four years with complete solar flux data is 99.2 ± 0.6 W m−2. The mean annual temperature at Lake Untersee was determined to be −10.6° ± 0.6°C. The annual degree-days above freezing for the five years were 9.7, 37.7, 22.4, 7.0, and 48.8, respectively, with summer (DJF) accounting for virtually all of this. For these five summers the average DJF temperatures were −3.5°, −1.9°, −2.2°, −2.6°, and −2.5°C. The maximum (minimum) temperatures were +5.3°, +7.6°, +5.7°, +4.4°, and +9.0°C (−13.8°, −12.8°, −12.9°, −13.5°, and −12.1°C). The average of the wind speed recorded was 5.4 m s−1, the maximum was 35.7 m s−1, and the average daily maximum was 15 m s−1. The wind speed was higher in the winter, averaging 6.4 m s−1. Summer winds averaged 4.7 m s−1. The dominant wind direction for strong winds is from the south for all seasons, with a secondary source of strong winds in the summer from the east-northeast. Relative humidity averages 37%; however, high values will occur with an average period of ~10 days, providing a strong indicator of the quasi-periodic passage of storms across the site. Low summer temperatures and high wind speeds create conditions at the surface of the lake ice resulting in sublimation rather than melting as the main mass-loss process.

Response of some vegetable crops to soil-applied halides

1992 ◽  
Vol 72 (4) ◽  
pp. 555-567 ◽  
Author(s):  
S. C. Sheppard ◽  
W. G. Evenden
Keyword(s):  
Key Words ◽  
Soil Surface ◽  
Competitive Interaction ◽  
The Other ◽  
Vegetable Crops ◽  
Tissue Concentrations ◽  
Industrial Pollutants ◽  
High Concentrations ◽  
Corn Kernels ◽  
Key Words Fluoride

The halide elements are environmentally important and share some common attributes. The heaviest, I, and the lighest, F, are quite toxic and are important industrial pollutants. They are also effectively retained in soils. The others, Cl and Br, can be accumulated to high concentrations in plants, are used in agriculture and are highly mobile in soils. This study investigated the behaviour of the halides in plots, outdoor lysimeters, and laboratory sorption and excised-root experiments. Sorption on soil was ordered as F > I > Br > Cl. Concentrations in plants were generally ordered as CI ≥ Br > > F ≥ I, the inverse of the sorption ordering, as expected. Older tissues, which were also closest to the soil surface, had higher concentrations, and sequestered tissues, such as corn kernels and cabbage heads, had lower concentrations. There was evidence of competitive interaction among the halides and with soil anions such as phosphate and sulfate. This competition reduced the toxicity of I and modified tissue concentrations of the halides, P and S. Another interesting interaction was an increase in Cl and I sorption on soil solids when there were elevated levels or the other halides. Overall, the study of the halides in combination enhanced our understanding of their individual behaviours. Key words: Fluoride, chloride, bromide, iodide, vegetable

scholarly journals Glacier mass balances (1993–2001), Taylor Valley, McMurdo Dry Valleys, Antarctica

2006 ◽  
Vol 52 (178) ◽  
pp. 451-462 ◽  
Author(s):  
Andrew G. Fountain ◽  
Thomas H. Nylen ◽  
Karen L. MacClune ◽  
Gayle L. Dana
Keyword(s):  
Mass Balance ◽  
Piecewise Linear ◽  
Objective Assessment ◽  
Mcmurdo Dry Valleys ◽  
Dry Valleys ◽  
Mass Balances ◽  
Missing Measurements ◽  
Wind Speeds ◽  
Taylor Valley ◽  
Air Temperatures

AbstractMass balances were measured on four glaciers in Taylor Valley, Antarctica, from 1993 to 2001. We used a piecewise linear regression, which provided an objective assessment of error, to estimate the mass balance with elevation. Missing measurements were estimated from linear regressions between points and showed a significant improvement over other methods. Unlike temperate glaciers the accumulation zone of these polar glaciers accumulates mass in summer and winter and the ablation zone loses mass in both seasons. A strong spatial trend of smaller mass-balance values with distance inland (r2 = 0.80) reflects a climatic gradient to warmer air temperatures, faster wind speeds and less precipitation. Annual and seasonal mass-balance values range only several tens of millimeters in magnitude and no temporal trend is evident. The glaciers of Taylor Valley, and probably the entire McMurdo Dry Valleys, are in equilibrium with the current climate, and contrast with glacier trends elsewhere on the Antarctic Peninsula and in temperate latitudes.

scholarly journals Water tracks intensify surface energy and mass exchange in the Antarctic McMurdo Dry Valleys

2019 ◽  
Vol 13 (8) ◽  
pp. 2203-2219 ◽  
Author(s):  
Tobias Linhardt ◽  
Joseph S. Levy ◽  
Christoph K. Thomas
Keyword(s):  
Climate Change ◽  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Heat Fluxes ◽  
Dry Valleys ◽  
Sensible Heat ◽  
Net Radiation ◽  
Taylor Valley ◽  
The Antarctic

Abstract. The hydrologic cycle in the Antarctic McMurdo Dry Valleys (MDV) is mainly controlled by surface energy balance. Water tracks are channel-shaped high-moisture zones in the active layer of permafrost soils and are important solute and water pathways in the MDV. We evaluated the hypothesis that water tracks alter the surface energy balance in this dry, cold, and ice-sheet-free environment during summer warming and may therefore be an increasingly important hydrologic feature in the MDV in the face of landscape response to climate change. The surface energy balance was measured for one water track and two off-track reference locations in Taylor Valley over 26 d of the Antarctic summer of 2012–2013. Turbulent atmospheric fluxes of sensible heat and evaporation were observed using the eddy-covariance method in combination with flux footprint modeling, which was the first application of this technique in the MDV. Soil heat fluxes were analyzed by measuring the heat storage change in the thawed layer and approximating soil heat flux at ice table depth by surface energy balance residuals. For both water track and reference locations over 50 % of net radiation was transferred to sensible heat exchange, about 30 % to melting of the seasonally thawed layer, and the remainder to evaporation. The net energy flux in the thawed layer was zero. For the water track location, evaporation was increased by a factor of 3.0 relative to the reference locations, ground heat fluxes by 1.4, and net radiation by 1.1, while sensible heat fluxes were reduced down to 0.7. Expecting a positive snow and ground ice melt response to climate change in the MDV, we entertained a realistic climate change response scenario in which a doubling of the land cover fraction of water tracks increases the evaporation from soil surfaces in lower Taylor Valley in summer by 6 % to 0.36 mm d−1. Possible climate change pathways leading to this change in landscape are discussed. Considering our results, an expansion of water track area would make new soil habitats accessible, alter soil habitat suitability, and possibly increase biological activity in the MDV. In summary, we show that the surface energy balance of water tracks distinctly differs from that of the dominant dry soils in polar deserts. With an expected increase in area covered by water tracks, our findings have implications for hydrology and soil ecosystems across terrestrial Antarctica.

Geochemistry of contrasting stream types, Taylor Valley, Antarctica

2020 ◽  
Vol 133 (1-2) ◽  
pp. 425-448
Author(s):  
Russell S. Harmon ◽  
Deborah L. Leslie ◽  
W. Berry Lyons ◽  
Kathleen A. Welch ◽  
Diane M. McKnight
Keyword(s):  
Dissolved Oxygen ◽  
Austral Summer ◽  
Mineral Dissolution ◽  
Silicate Mineral ◽  
Cation Composition ◽  
Taylor Valley ◽  
Low Concentrations ◽  
Hyporheic Zones ◽  
Dry Valley ◽  
Geochemical Fingerprint

Abstract The McMurdo Dry Valley region is the largest ice-free area of Antarctica. Ephemeral streams flow here during the austral summer, transporting glacial meltwater to perennially ice-covered, closed basin lakes. The chemistry of 24 Taylor Valley streams was examined over the two-decade period of monitoring from 1993 to 2014, and the geochemical behavior of two streams of contrasting physical and biological character was monitored across the seven weeks of the 2010–2011 flow season. Four species dominate stream solute budgets: HCO3–, Ca2+, Na+, and Cl–, with SO42–, Mg2+, and K+ present in significantly lesser proportions. All streams contain dissolved silica at low concentrations. Across Taylor Valley, streams are characterized by their consistent anionic geochemical fingerprint of HCO3 &gt; Cl &gt; SO4, but there is a split in cation composition between 14 streams with Ca &gt; Na &gt; Mg &gt; K and 10 streams with Na &gt; Ca &gt; Mg &gt; K. Andersen Creek is a first-order proglacial stream representative of the 13 short streams that flow &lt;1.5 km from source to gage. Von Guerard is representative of 11 long streams 2–7 km in length characterized by extensive hyporheic zones. Both streams exhibit a strong daily cycle for solute load, temperature, dissolved oxygen, and pH, which vary in proportion to discharge. A well-expressed diurnal co-variation of pH with dissolved oxygen is observed for both streams that reflects different types of biological control. The relative consistency of Von Guerard composition over the summer flow season reflects chemostatic regulation, where water in transient storage introduced during times of high streamflow has an extended opportunity for water-sediment interaction, silicate mineral dissolution, and pore-water exchange.

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