Roundup: Decaying Matter, Glacial Bacteria, and CO2 Uptake

Transport of Nutrients and Decaying Matter by Rivers and Streams

From “Intermittent Rivers and Ephemeral Streams”: “The hydrological regimes of most intermittent rivers and ephemeral streams (IRES) include the alternation of wet and dry phases in the stream channel and highly dynamic lateral, vertical, and longitudinal connections with their adjacent ecosystems. Consequently, IRES show a unique ‘biogeochemical heartbeat’ with pulsed temporal and spatial variation in nutrient and organic matter inputs, in-stream processing, and downstream transport. Given that IRES are widespread, their improper consideration may cause inaccurate estimation of nutrient and carbon fluxes in river networks… Our purpose is to contribute to the flourishing knowledge and research on the biogeochemistry of IRES by providing a comprehensive view of nutrient and organic matter dynamics in these ecosystems.”

Read more about the findings here.

Photo of intermittent river in Boliva
An intermittent river in Bolivia (Source: Thibault Datry‏/Twitter).


Glacial Bacteria Originated on Slopes Near Alaskan Glacier

From Microbiology Ecology: “Although microbial communities from many glacial environments have been analyzed, microbes living in the debris atop debris-covered glaciers represent an understudied frontier in the cryosphere. The few previous molecular studies of microbes in supraglacial debris have either had limited phylogenetic resolution, limited spatial resolution (e.g. only one sample site on the glacier) or both. Here, we present the microbiome of a debris-covered glacier across all three domains of life, using a spatially-explicit sampling scheme to characterize the Middle Fork Toklat Glacier’s microbiome from its terminus to sites high on the glacier. Our results show that microbial communities differ across the supraglacial transect, but surprisingly these communities are strongly spatially autocorrelated, suggesting the presence of a supraglacial chronosequence… We use these data to refute the hypothesis that the inhabitants of the glacier are randomly deposited atmospheric microbes, and to provide evidence that succession from a predominantly photosynthetic to a more heterotrophic community is occurring on the glacier.”

Learn more about glacial bacteria here.

Topographic map of bacteria sample sites
Topographic map of bacteria sample sites on the Middle Fork Toklat Glacier (Source: Darcy et al.).


Simulated High Alkalinity Glacial Runoff Increases CO2 Uptake in Alaska

From Geophysical Research Letters: “The Gulf of Alaska (GOA) receives substantial summer freshwater runoff from glacial meltwater. The alkalinity of this runoff is highly dependent on the glacial source and can modify the coastal carbon cycle. We use a regional ocean biogeochemical model to simulate CO2 uptake in the GOA under different alkalinity-loading scenarios. The GOA is identified as a current net sink of carbon, though low-alkalinity tidewater glacial runoff suppresses summer coastal carbon uptake. Our model shows that increasing the alkalinity generates an increase in annual CO2 uptake of 1.9–2.7 TgC/yr. This transition is comparable to a projected change in glacial runoff composition (i.e., from tidewater to land-terminating) due to continued climate warming. Our results demonstrate an important local carbon-climate feedback that can significantly increase coastal carbon uptake via enhanced air-sea exchange, with potential implications to the coastal ecosystems in glaciated areas around the world.”

Read more about the study here.

Photo of the Gulf of Alaska from space
The Gulf of Alaska from space (Source: NASA Goddard Images/Twitter).


When Rivers Meet the Sea: Carbon Cycling in the Gulf of Alaska

The Gulf of Alaska has numerous glacial inputs (Source: Jennifer Questel).

When rivers meet the sea, the sediment they carry becomes mixed into the ocean, where it makes quite a splash, biogeochemically speaking. In the subarctic North Pacific Ocean, for example, iron-rich sediment delivered from the continental margin spurs a wintertime phytoplankton bloom over 900 kilometers offshore. The presence of these terrigenous particles is felt up the food chain— the higher levels of iron in the water support larger diatom populations, which means more snacking for copepods, a type of zooplankton.

In the Gulf of Alaska, glacial meltwater is an important source of terrestrial particles. A recent study by Jessica Turner, Jessica Pretty, and Andrew McDonnell optically measured particles in the northern Gulf of Alaska, an area with extensive glacial inputs. This technique allowed the researchers to collect massive amounts of data with minimal lab work, maximizing the area they could survey, Jessica Pretty told GlacierHub. Their instrument measured a range of particle sizes, from some too small to be seen by the naked eye to others as large as paper clips.

Researcher Jessica Turner works with the optical profiling instrument (Source: Jennifer Questel).

Pretty and her coauthors found that in the Gulf of Alaska, particle concentrations are denser in two main places: where glaciers and rivers flow into the Gulf, and offshore, near the continental shelf break, where they are buoyed by waves, currents and tidal action. These small particles wield great influence, increasing biological productivity at the shelf break.

“The Gulf of Alaska is an interesting region,” said Pretty. “It has major freshwater input seasonally from melting glaciers and river runoff that eventually joins with Pacific waters and makes its way toward the Arctic.” The recent findings illuminate particle distribution in the northern Gulf of Alaska, yielding clues about how climate change may affect carbon cycling in the Gulf and parallel ocean systems.

Beyond local significance to the Gulf of Alaska ecosystem, the influence of these river-borne terrestrial particles scales up— globally, such sediment inputs impacts the carbon cycle, which regulates climate. The bits of rock Pretty tracked in the Gulf of Alaska are essentially tiny bundles of carbon, and when these bundles sink in the ocean, they drive what scientists have termed the “biological pump,” the process by which the ocean cycles organic and inorganic carbon, and sequesters carbon dioxide in the deep ocean.

Jessica Pretty observes an instrument deployment during a research cruise (Source: Jennifer Questel).

Because carbon dioxide is constantly exchanged between the upper layers of the ocean and lower levels of the atmosphere, concentrations become equal in the shallow ocean and low atmosphere over time. However, sinking particles remove carbon from this exchange. “The biological pump allows the ocean to store more carbon than it would be able to just from equilibration,” explained Pretty.

The ocean absorbs a quarter of the carbon dioxide released into the atmosphere each year, and so as carbon is pumped into the atmosphere, levels in the ocean increase in tandem. This leads to ocean acidification, which threatens many marine species. However, terrestrial carbon sequestration practices, like soil conservation and wildfire suppression, may be an important element of climate change mitigation.

Particle concentrations are high near glacial inputs, such as from the Fourpeaked Glacier (Source: Jennifer Questel).

As global climate warms and glaciers melt, higher glacial inputs will carry more sediment to the Gulf of Alaska and analogous ecosystems around the world. These minute particles will ramp up the global biological pump, increase carbon sequestration, and lead to a myriad of impacts yet unknown. In addition, seasonal changes, like an earlier springtime, may also spur earlier phytoplankton blooms, changing the dynamics of life in the sea. Through the movement of minuscule specks of rock, the Gulf of Alaska, and ultimately the whole ocean, will change.

Roundup: Greenland Earthquake, Mural Restoration, and Phytoplankton

Greenland Earthquake Triggers Landslide-Induced Tsunami

From Temblor: “Over the weekend, a M=4.1 earthquake on Greenland’s western coast caused a massive landslide, triggering a tsunami that inundated small settlements on the coast. At this stage, four people are feared to have died, nine others were injured, and 11 buildings were destroyed. Glacial earthquakes are a relatively new class of seismic event, and are often linked to the calving of large outlet glaciers.”

You can read more about the glacial earthquake in Greenland here.

Remnants of Nuugaatsiaq, Greenland, after the glacial earthquake (Source: Stephen Gadd/Cphpost).

Mural Restoration at Glacier National Park

From Hockaday Museum of Art: “Early visitors to Glacier Park Lodge were treated to architectural and visual grandeur inside the building that was almost as expansive as the surrounding landscape. The scenic panels covered hundreds of square feet and appeared in a 1939 Glacier Park Lodge inventory as ’51 watercolor panels.’ In September of 2012, Leanne Brown donated the murals to the Hockaday in memory of her grandparents, Leona and Robert Brown, who had saved and restored 15 of the murals.”

Learn more about the restored murals here.

Restoration process of the murals (Glacier National Park/Hockaday).

Phytoplankton Growth in Alaska

From AGU Publications: “Primary productivity in the Gulf of Alaska is limited by availability of the micronutrient iron (Fe). Identifying and quantifying the Fe sources to this region are therefore of fundamental ecological importance. Understanding the fundamental processes driving nutrient fluxes to surface waters in this region is made even more important by the fact that climate and global change are impacting many key processes, which could perturb the marine ecosystem in ways we do not understand.”

Read more about phytoplankton growth in the Gulf of Alaska here.

Springtime brings a massive bloom of phytoplankton in the Gulf of Alaska (NASA/Google Images).


Photo Friday: A Look at Wolverine Glacier

Wolverine Glacier is a valley glacier with maritime climate and high precipitation rates situated in the coastal mountains of Alaska’s Kenai Peninsula. This glacier has been named a “reference glacier” by the World Glacier Monitoring Service because it has been monitored and observed since 1965/66. A majority of the U.S. government’s climate research is taken from 50 years of glacier studies from the United States Geological Survey (USGS). Scientists first decided to take measurements of Wolverine Glacier’s surface mass balance in 1966, using these measurements, as well as local meteorology and runoff data, to estimate glacier-wide mass balances, according to USGS. This data, which makes up the longest continuous set of mass-balance data in North America, allows scientists to better understand glacier dynamics and hydrology, as well as the glaciers’ response to climate change.

As temperatures rise, the retreat of glaciers in Alaska is contributing to global sea-level rise. The Wolverine Glacier has been experiencing more variability in winter temperatures, and scientists are continuing to evaluate how glaciers like the Wolverine respond to climate change. Take a look at GlacierHub’s collection of images from Wolverine Glacier.


Scientists checking ablation stakes at Wolverine Glacier (Source: USGS).


A weather station set up to measure the spatial differences in climate that influence mass balance (Source: USGS).


Researchers use ground penetrating radar to determine the depth of the snow on Wolverine Glacier (Source: USGS).


The crevassed surface of Wolverine Glacier shows layers within the ice and snow (Source: USGS).


Satellites Detect Both Steady and Accelerated Ice Loss

A new study published in Geophysical Research Letters reports the findings of a pair of satellites that measure gravity to get a clearer picture of the continued ice mass loss in Greenland, the Gulf of Alaska, and the Canadian Arctic Archipelago. The study found accelerated ice loss in the Arctic, and steady loss in Alaska, which will have significant implications for sea level rise globally.

Depiction of the GRACE satellites. (Source: NASA Jet Propulsion Laboratory)
Depiction of the GRACE satellites. (Source: NASA Jet Propulsion Laboratory)

The researchers, Christopher Harig and Frederik J. Simmons, both of Princeton University, analyzed data from the two satellites, called the Gravity Recovery and Climate Experiment (GRACE), in order to not only find the current state of ice mass within glaciers and ice sheets, but the changes in mass since 2003.

GRACE’s dual satellites circle the Earth together, and minute fluctuations in their orbit serve as a basis for measuring the Earth’s gravitational field. The two are separated by approximately 137 miles, and as they fluctuate with the changing gravitational pull, the distance between the two varies slightly. (The two satellites are nicknamed Tom and Jerry, a reference to the cartoon cat and mouse.)

Coupling the differing distances with precise GPS locations, GRACE is able to provide a view of the Earth’s gravity with “unprecedented accuracy” as NASA says. This level of detail allows researchers to easily find even minute trends in mass changes.

GRACE is more commonly used over large areas, such as ice sheets, but in this research the authors studied areas “near the [lower] limit that can be resolved by GRACE data.” After thermal expansion, mountain glaciers and ice caps are the second highest contributor to sea level rise, making accurate and efficient study of the mass loss from smaller areas critical for future sea level projections.

The researchers found that the glacial ice on the north region of the Gulf of Alaska was decreasing at a faster rate than the south region. GRACE detected an unexpectedly large ice loss in 2009 which the authors attribute to a lowered albedo after the eruption of Mount Redoubt.

NASA image of Eureka Sound on Ellesmere Island. (Source: Stuart Rankin/Flickr)
NASA image of Eureka Sound on Ellesmere Island. (Source: Stuart Rankin/Flickr)

The Canadian Archipelago as a whole has been losing ice mass steadily. Within it, the Ellesmere Island region was stable in 2003, when the data was first collected, but mass loss has been accelerating since. In 2013, the researchers found that the mass loss within the Ellesmere Island region had dramatically accelerated, but has since continued closer to average. Baffin Island, the second area studied within the Archipelago, also saw significant ice loss but not at the same rate as Ellesmere.

Greenland saw “an order of a magnitude” more total volume ice loss than Baffin and Ellesmere. Partially due to its sheer size, ice loss there is significant; in the previous decade the largest land-based contributor to sea level rise has been Greenland.

As ice mass loss continues in these regions due to natural variability and climate change, it will be important to have accurate and localized data to better prepare for the corresponding sea level rise.  

Visual depiction of sea level rise. (Source: go_greener_oz/Flickr)
Visual depiction of sea level rise. (Source: go_greener_oz/Flickr)

“Worldwide, on the order of 500 million people could be directly impacted by rising sea level by the end of this century. The human impact is combined with a large financial impact as well. So regardless of where people live, I think the impacts of ice loss and sea level rise will be easily seen in the future,” co-author Christopher Harig said in an email to GlacierHub.