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Title: Eight genome sequences of bacterial environmental isolates from Marr Pond, Antarctica
ABSTRACT Inland meltwater ponds are common throughout the dry valley region of Antarctica, with seasonal meltwater inputs driving their biogeochemistry. Here, we report the genomic sequences of eight environmental bacterial isolates covering three major phyla from Marr Pond, Taylor Valley, Antarctica. more »« less
ABSTRACT Sediments in cryoconite holes and meltwater streams in the McMurdo Dry Valleys, Antarctica, provide both substrates and conditions that support life in an arid polar desert. Here, we report the genomic sequences of eight environmental, bacterial isolates from Canada Glacier cryoconite holes and stream. These isolates span three major phyla.
Beadling, R. L.; Krasting, J. P.; Griffies, S. M.; Hurlin, W. J.; Bronselaer, B.; Russell, J. L.; MacGilchrist, G. A.; Tesdal, J. ‐E.; Winton, M.
(, Journal of Geophysical Research: Oceans)
Abstract We use two coupled climate models, GFDL‐CM4 and GFDL‐ESM4, to investigate the physical response of the Southern Ocean to changes in surface wind stress, Antarctic meltwater, and the combined forcing of the two in a pre‐industrial control simulation. The meltwater cools the ocean surface in all regions except the Weddell Sea, where the wind stress warms the near‐surface layer. The limited sensitivity of the Weddell Sea surface layer to the meltwater is due to the spatial distribution of the meltwater fluxes, regional bathymetry, and large‐scale circulation patterns. The meltwater forcing dominates the Antarctic shelf response and the models yield strikingly different responses along West Antarctica. The disagreement is attributable to the mean‐state representation and meltwater‐driven acceleration of the Antarctic Slope Current (ASC). In CM4, the meltwater is efficiently trapped on the shelf by a well resolved, strong, and accelerating ASC which isolates the West Antarctic shelf from warm offshore waters, leading to strong subsurface cooling. In ESM4, a weaker and diffuse ASC allows more meltwater to escape to the open ocean, the West Antarctic shelf does not become isolated, and instead strong subsurface warming occurs. The CM4 results suggest a possible negative feedback mechanism that acts to limit future melting, while the ESM4 results suggest a possible positive feedback mechanism that acts to accelerate melt. Our results demonstrate the strong influence the ASC has on governing changes along the shelf, highlighting the importance of coupling interactive ice sheet models to ocean models that can resolve these dynamical processes.
Bergstrom, Anna; Gooseff, Michael N.; Myers, Madeline; Doran, Peter T.; Cross, Julian M.
(, The Cryosphere)
Abstract. The McMurdo Dry Valleys (MDVs) of Antarctica are a polar desertecosystem consisting of alpine glaciers, ice-covered lakes, streams, andexpanses of vegetation-free rocky soil. Because average summer temperaturesare close to 0 ∘C, theMDV ecosystem in general, and glacier melt dynamics in particular, are both closely linked to the energy balance. A slightincrease in incoming radiation or change in albedo can have large effects onthe timing and volume of meltwater. However, the seasonal evolution orspatial variability of albedo in the valleys has yet to fully characterized.In this study, we aim to understand the drivers of landscape albedo changewithin and across seasons. To do so, a box with a camera, GPS, andshortwave radiometer was hung from a helicopter that flew transects four to fivetimes a season along Taylor Valley. Measurements were repeated over threeseasons. These data were coupled with incoming radiation measured at sixmeteorological stations distributed along the valley to calculate thedistribution of albedo across individual glaciers, lakes, and soilsurfaces. We hypothesized that albedo would decrease throughout the australsummer with ablation of snow patches and increasing sediment exposure on theglacier and lake surfaces. However, small snow events (<6 mm waterequivalent) coupled with ice whitening caused spatial and temporalvariability of albedo across the entire landscape. Glaciers frequentlyfollowed a pattern of increasing albedo with increasing elevation, as well asincreasing albedo moving from east to west laterally across the ablationzone. We suggest that spatial patterns of albedo are a function of landscapemorphology trapping snow and sediment, longitudinal gradients in snowfallmagnitude, and wind-driven snow redistribution from east to west alongthe valley. We also compare our albedo measurements to the MODIS albedo productand found that overall the data have reasonable agreement. The mismatch inspatial scale between these two datasets results in variability, which isreduced after a snow event due to albedo following valley-scale gradients ofsnowfall magnitude. These findings highlight the importance of understandingthe spatial and temporal variability in albedo and the close coupling ofclimate and landscape response. This new understanding of landscape albedocan constrain landscape energy budgets, better predict meltwater generationon from MDV glaciers, and how these ecosystems will respond to changingclimate at the landscape scale.
Abstract Global Navigation Satellite System (GNSS) observations and ground-based timelapse photography obtained over the record-high 2019/2020 melt season are combined to characterise the flexure and fracture behaviour of a previously formed doline on George VI Ice Shelf, Antarctica. The GNSS timeseries shows a downward vertical displacement of the doline centre with respect to the doline rim of ~60 cm in response to loading from a central meltwater lake. The GNSS data also show a tens-of-days episode of rapid-onset, exponentially decaying horizontal displacement, where the horizontal distance between the doline rim and its centre increases by ~70 cm. We interpret this event as the initiation and/or widening of a fracture, aided by stress perturbations associated with meltwater loading in the doline basin. Viscous flexure modelling indicates that the meltwater loading generates tensile surface stresses exceeding 75 kPa. This, together with our timelapse photos of circular fractures around the doline, suggests the first such documentation of meltwater-loading-induced ‘ring fracture’ formation on an ice shelf, equivalent to the fracture type proposed as part of the chain-reaction lake drainage process involved in the 2002 breakup of the Larsen B Ice Shelf.
Trusel, Luke D.; Pan, Zhuolai; Moussavi, Mahsa
(, Geophysical Research Letters)
Abstract Surface melting and lakes are common to Antarctic ice shelves, and their existence and drainages have been invoked as a precursor for ice shelf collapse. Here, we present satellite observations over 2014–2020 of repeated, rapid drainages of a supraglacial lake at the grounding zone of Amery Ice Shelf, East Antarctica. Post‐drainage imagery in 2018 reveals lake bottom features characteristic of rapid, vertical lake drainage. Observed lake volumes indicate drainages are not associated with a threshold meltwater volume. Instead, drainages typically coincide with periods of high daily tidal amplitude, suggesting hydrofracture is assisted by tidally forced ice flexure inherent to the ice shelf grounding zone. Combined with observations of widespread grounding zone lake drainages on Amery, these findings indicate ice shelf meltwater accumulation may be inhibited by grounding zone drainage events, thus representing a potential stabilizing mechanism despite enhanced melting common to these regions.
@article{osti_10638259,
place = {Country unknown/Code not available},
title = {Eight genome sequences of bacterial environmental isolates from Marr Pond, Antarctica},
url = {https://par.nsf.gov/biblio/10638259},
DOI = {10.1128/mra.00135-25},
abstractNote = {ABSTRACT Inland meltwater ponds are common throughout the dry valley region of Antarctica, with seasonal meltwater inputs driving their biogeochemistry. Here, we report the genomic sequences of eight environmental bacterial isolates covering three major phyla from Marr Pond, Taylor Valley, Antarctica.},
journal = {Microbiology Resource Announcements},
volume = {14},
number = {6},
publisher = {Microbiology Resource Announcements},
author = {Smith, Heidi J and Dieser, Markus and M_Foreman, Christine},
editor = {Thrash, J Cameron}
}
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