Roundup: Grounding Lines, Methane-Oxidizing Bacteria and Grazing Patterns

Grounding Lines of Antarctic Glaciers Show Fast Retreat

From Nature Geoscience, “Grounding lines are a key indicator of ice-sheet instability, because changes in their position reflect imbalance with the surrounding ocean and affect the flow of inland ice. Although the grounding lines of several Antarctic glaciers have retreated rapidly due to ocean-driven melting, records are too scarce to assess the scale of the imbalance. Here, we combine satellite altimeter observations of ice-elevation change and measurements of ice geometry to track grounding-line movement around the entire continent, tripling the coverage of previous surveys. Between 2010 and 2016, 22%, 3% and 10% of surveyed grounding lines in West Antarctica, East Antarctica and at the Antarctic Peninsula retreated at rates faster than 25 m yr−1 (the typical pace since the Last Glacial Maximum) and the continent has lost 1,463 km2 ± 791 km2 of grounded-ice area.”

Discover more about Antarctica’s melting situation here.

The calving front of an ice shelf in West Antarctica as seen from above (Source: NASA/Flickr)


Glacier Melt Exposes Land for Methane-Oxidizing Bacteria

From Oxford Academic: “Methane (CH4) is one of the most abundant greenhouse gases in the atmosphere and identification of its sources and sinks is crucial for the reliability of climate model outputs. Although CH4 production and consumption rates have been reported from a broad spectrum of environments, data obtained from glacier forefields are restricted to a few locations. We report the activities and diversity of Methane-Oxidizing Bacteria along a Norwegian sub-Arctic Glacier Forefield using high-throughput sequencing and gas flux measurements. The overall results showed that the methanotrophic community had similar trends of increased CH4 consumption and increased abundance as a function of soil development and time of year when glaciers retreat.”

Read more about the relationship between methane and glacier retreat here.

Methane-oxidizing Bacteria Methylosinus Trichosporium (Source: Ezra Kulczycki/ PNAS)
Methane-oxidizing Bacteria Methylosinus Trichosporium (Source: Ezra Kulczycki/ PNAS).


Grazing Patterns in Glacier-fed Wetlands

In PLOS ONE, “Grazing areas management is of utmost importance in the Andean region. In these harsh mountains, unique and productive wetlands sustained by glacial water streams are of utmost importance for feeding cattle herds during the dry season. After the colonization by the Spanish, a shift in livestock species has been observed, with the introduction of exotic species such as cows and sheep, resulting in a different impact on pastures compared to native camelid species—llamas and alpacas. Our results suggest that the access to market influenced pastoralists to reshape their herd composition, by increasing the number of sheep. They also suggest that community size increased daily grazing time in pastures, therefore intensifying the grazing pressure.”

Explore the influence of glacier meltwater on wetland size and herd composition here.

Llama in a sea of sheep grazing in a farm (Source: Brianne Hughes/ Pinterest )
A llama in a sea of sheep grazing on a farm (Source: Brianne Hughes/ Pinterest).

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