Geochemical Evolution of Meltwater from Glacier Snow to Proglacial Lake

Glaciers around the world are making headlines for their rapid retreat due to warming. Unlike some of these glaciers, however, dry valley glaciers, while accumulating only about 10 cm of snow annually, are neither retreating nor warming. Sarah Fortner, a geochemistry professor at Wittenberg University in Ohio, examined the meltwater of Canada Glacier, a dry valley glacier located in the Taylor Valley of Antarctica, and published a paper focused on two of its proglacial streams, Anderson Creek and Canada Stream.

Canada Glacier flowing into the Taylor Valley, Antarctica (Source: Anthony Powell).

Melting of glaciers develops an important part of a glacier’s anatomy known as “supraglacial streams,” which are conduits of water on top of glaciers. These supraglacial streams often become a source of water for “proglacial streams,” like the Anderson Creek and Canada Stream, narrow channels of rivers that issue from glaciers supply water to lakes located below the glaciers.

Fortner studied the meltwater of Canada Glacier during the 2001 to 2002 austral summer in the southern hemisphere (from November to March) and the contribution of the proglacial stream and glacial surface to water in Lake Hoare, which is located in front of Canada Glacier.

In her study, Fortner determines the crucial role of the wind in redistributing the geochemistry of the glacial surface as well as the two proglacial streams. By looking at the geochemistry of the two proglacial streams and the role of the wind in bringing valley sediments to the supraglacial and ultimately proglacial streams, Fortner found that the glaciers that contributed to the proglacial lakes are not dilute like glacier snow.

Large pond formed from supraglacial melt on the surface of Canada Glacier. (Source: Fortner)

Contrary to expectations, the chemistry between the two streams was quite different. “While they are roughly five miles apart, they were very different,” she told GlacierHub. “Located on the east side of the glacier, Canada Stream was teaming with life, with multiple mosses, lichen, algae, and invertebrates. If you were to press your hand into these, it would feel like a sponge. On the west side of the glacier, Anderson Creek looks barren in comparison. There is life in the stream, but not as abundant or diverse as the Canada Stream.”

In an attempt to find the source of the difference, Fortner and a team of scientists sampled water from supraglacial channels with high discharge for chemical analysis. Through this analysis, Fortner aimed to map the evolution of the chemicals in the meltwater at Canada Glacier from unmelted glacier snow to supraglacial streams to proglacial streams and finally to Lake Hoare located in front of the glacier.

Taylor Valley and Lake Hoare (Source: 77DegreesSouth).

With the chemical mass balance analysis of the samples from the glacier, Fortner first wanted to see whether the chemical composition of the supraglacial stream would be diluted like the unmelted glacier snow, their primary precipitation. According to Fortner, unmelted glacier snow would naturally be very dilute, with a low concentration of any chemical solute, and we would expect the same level of chemical concentration from the supraglacial streams, located on top of the glacier body itself and created as a result of glacier snow melting. However, she found that supraglacial streams were rich in major ions like calcium, sodium, and sulfate. 

“This begins to highlight the importance of wind-blown sediment as control of water chemistry in these Antarctic ecosystems,” Fortner said.

In her paper, she explains that the strong west to east Föhn wind (Foehn wind), a parcel of dry and warm air moving down the lee (downwind side) of the mountain, brought sediments from the floor of Taylor Valley, abundant with carbonate ( CO3(2-)) and gypsum (CaH4O6S) minerals, which are the sources of the high calcium (Ca2+) and sulfate ion (SO2-4) found in the supraglacial streams. In short, the wind delivered sediment that influenced the chemistry of the streams on the surface of the glacier.

Diagram of Föhn wind (Source: ipfs).

“Both sides of the valley floor contributed to the sediment received on the glacier surface which explained major chemical differences found in supraglacial and proglacial streams versus the original unmelted snow. It is also clear that the Föhn wind coming off of the ice sheet had the greatest influence on depositing chemistry,” Fortner explained.

Furthermore, the west to the east direction of the wind causes a difference in chemical composition between the proglacial streams in the western and eastern sides of Canada Glacier, preferentially depositing more sulfate in the western proglacial streams (Anderson Creek) than in the eastern proglacial streams (Canada Stream).

“As a result of the west to east wind, supraglacial streams flowing into Anderson Creek have much higher concentrations of both calcium and sulfate than supraglacial streams flowing into Canada Stream,” Fortner explained.

Map of the Ross Sea. Lake Hoare is located within the Taylor Valley, showing its proximity to Ross Sea. (Sources: USGSantarctic.eu).

The chemical deliveries from the stream channel to the proglacial lake is crucial to examine, as Anderson Creek contributes over 40 percent of the water to Lake Hoare, the final recipient of the meltwater from Canada Glacier, during the low-melt season. However, Fortner said it is just as important to examine the chemical deliveries from the glacial surface (direct runoff).

“While one would think streams would deliver far more chemistry, as glaciers and their direct runoff are typically dilute, glacier surface can be just as important source of chemistry because of the low accumulation and wind delivered sediment,” she added.

Dry valley glaciers are unique in that the glacier surface is an important contributor of chemistry to downstream ecosystems. Unlike many other glaciers, it isn’t just about chemistry from stream channels, but also about glacier surfaces. If more melt continues in response to the wind, this could result in potential changes in the chemical delivery into Lake Hoare. Furthermore, such changes can extend to the continental outline of Antarctica into Ross Sea, the southern extension of the Pacific Ocean.

 

Roundup: Putin’s Arctic Visit, Glacier Tours, and Pollutants

Roundup: Putin, Glacier Tours and Pollutants

Vladimir Putin Visits Arctic Glacier

From The Telegraph: “President Vladimir Putin on Wednesday visited an Arctic archipelago, part of Russia’s efforts to reaffirm its foothold in the oil-rich region. On a tour of the Franz Josef Land archipelago, a sprawling collection of islands where the Russian military has recently built a new runway and worked to open a permanent base, Mr Putin emphasized the need to protect Russia’s economic and security interests in the Arctic… During the visit, Putin inspected a cavity in a glacier that scientists use to study permafrost. He also spoke with environmental experts who have worked to clean the area of Soviet-era debris.”

Read more about Putin’s glacier tour here.

Vladimir Putin visited an Arctic glacier (Source: Creative Commons).
Vladimir Putin visited an Arctic glacier (Source: Kremlin/Creative Commons).

 

Fees Charged to Visit Alaskan Glacier

From adn.com: “Matanuska Glacier is the most user-friendly glacier in Alaska — one of few major ice sheets in the world that visitors can drive to and explore on foot. The glacier sits along a scenic stretch of the Glenn Highway about two hours from Anchorage, a frozen river sprawling almost 30 miles from the 13,000-foot heights of the Chugach Mountains to a toe hundreds of feet deep and miles wide that offers unique glimpses of usually buried formations. The only road-accessible route to the ice is through property owned by Matanuska Glacier Park LLC… Before November, a tour was just one option for glacier-goers who wanted to spend several hours with a guide on a trail that loops past frozen caves, tunnels and canyons and avoids hidden crevasses, water-filled pits or holes that can descend hundreds of feet into the ice. But that month, Matanuska Glacier Park began requiring any first-time winter visitor without glacier travel experience to pay for a tour — like it or not.”

Learn more about the new fees here.

Matanuska Glacier terminus (Source: Sbork/Creative Commons).
Matanuska Glacier terminus (Source: Sbork/Creative Commons).

 

Downward Trend of Organic Pollutants in Antarctica

From Chemosphere: “Passive air samplers were used to evaluate long-term trends and spatial distribution of trace organic compounds in Antarctica. Duplicate PUF disk samplers were deployed at six automatic weather stations in the coastal area of the Ross sea (East Antarctica), between December 2010 and January 2011, during the XXVI Italian Scientific Research Expedition… In general, the very low concentrations reflected the pristine state of the East Antarctica air. Backward trajectories indicated the prevalence of air masses coming from the Antarctic continent. Local contamination and volatilization from ice were suggested as potential sources for the presence of persistent organic pollutants in the atmosphere.”

Read more about organic pollutants here.

The Ross Sea in Antarctica (Source: Cortto/Creative Commons).
The Ross Sea in Antarctica (Source: Cortto/Creative Commons).