Subglacial Meltwater Boosts Greenland Ecosystems and Locks Carbon

Following news of the arrival of a Manhattan-sized iceberg from a retreating glacier next to a village in Greenland, a recent paper published in the Journal of Geophysical Research has unveiled new research on how subglacial meltwater in Greenland is pumping nutrients and carbon from the deep sea to drive a boom of microorganisms in the upper layers. This effect fuels the ecosystems around it and impacts carbon cycling within the fjords and ocean close to the glaciers, further increasing the carbon uptake from the atmosphere.

Since 2002, Greenland has lost around 270 billion tons of ice per year. The glaciers and ice sheets of Greenland are key to the magnitude of future sea level rise, prompting scientists and researchers from around the globe to travel to the glacier-laced land to study and measure the physics of glacier melting and retreat. A team of researchers from Hokkaido University, led by Naoya Kanna and Shin Sugiyama, found a new perspective to understand the interactions of glaciers with ecosystems under a changing climate.

Bowdoin Glacier and Fjord. Bowdoin is a tidewater glacier in northwestern Greenland (Source: Shin Sugiyama).

Since 2012, the team’s focus has been measurements of the ice in the region, with specific interest in the mechanisms of the Bowdoin glacier’s rapid retreat. Shin Sugiyama, the second author of the paper, wrote to GlacierHub, “We recognized the glacier-ocean interaction as the key process and expanded our activity to the ocean.”

The researchers moved from geophysical measurements to geochemical measurements over time. They started to camp in the nearby village of Qaanaaq beginning in the summer of 2016, surveying the water temperature, salinity, ocean currents and other physical properties.

A researcher collects water samples from the front of Bowdoin Glacier using a fishing rod (Source: Shin Sugiyama).

They collected biogeochemical samples from the top of Bowdoin Glacier, the plume along the glacier front, and nearby fjords. They found that the plume water is more turbid, and its chemical composition is significantly different from waters in other locations due to a higher concentration of nutrients and salts. At the same time, phytoplankton blooms were also detected.

They then found an underwater nutrient and carbon transfer route that may explain these observations. Sugiyama describes the transfer as a “nutrient pump.”

At the bottom of the sea, due to the gravity and ocean currents, there are water flows from the fjord moving toward the glacier front. These flows carry a lot of descended nutrients and dissolved carbon. There is also subglacial freshwater discharge that is turbid because of the subglacial weathering. The two flows meet at the deep sea and create massive fluxes of sediments along the glacier fronts.

When the sediment-laden upwell water reaches the sea surface, it forms an opaque layer below the relatively fresher sea surface water. During the upwelling process, the mixture of subglacial discharge water and flows from the fjord pumps nutrients and carbon from the deep water to the upper layers.

Schematics of the nutrient and carbon rich subsurface plume water formation at the front of Bowdoin Glacier (Source: Kanna et al.).

Later, phytoplankton blooms were observed in between the sea surface and the near surface plume water. Phytoplankton are plant-like marine microorganisms at the base of the ocean’s food pyramid. These tiny organisms absorb nutrients and carbon to fuel their growth. Some of the nutrients and carbon fall to the bottom with the phytoplankton when they wither. Other portions of the nutrients and carbon further pass into the food web through organisms that graze on the phytoplankton.

The growth burst of the phytoplankton went unnoticed until recent years. Through their analysis of samples from supraglacial meltwater, proglacial stream discharge, fjord surface water, and plume surface water, the authors identify a distinct vertical distribution of nutrients and carbon along the centerline of the fjord. The data prove that the upwelling associated with the subglacial discharge has been pumping the nutrients and carbon from the deep water toward the surface, catalyzing the formation of phytoplankton blooms.

As the planet warms, glacier melting is increasing in Greenland. For its implication on their findings, Sugiyama said, ”Our study implies that nutrient supply to fjord surface water is enhanced by an increase in meltwater discharge under the warming climate. This results in higher primary production [of microorganisms]. On the other hand, turbid plume water also disturbs the production by limiting light availability in water.” He noted the team will continue their research to understand how these positive and negative impacts counterbalance.

The researcher conduct measurements near the Bowdoin Glacier front with a boat operated by a local hunter (Source: Shin Sugiyama).

The study not only showed a critical role of freshwater discharge in the primary productivity of microorganisms in front of the glaciers, but it also indicated that changes in glacier melt might impact the fjord ecosystems.

“Tidewater glacier front is a biological ‘hot spot.’ We see many birds and sea mammals near the front of Bowdoin Glacier. Change in the ecosystem is not clear at this moment, but we suspect such a highly productive ecosystem is sensitive to the warming Arctic climate,” Sugiyama said.

The ocean also acts as an immense carbon sink, which scientists need to explore. This finding may provide ideas for how carbon transfers within the marine ecosystem.

Sugiyama added, “A possible influence on the carbon cycle is more carbon storage in the ocean when primary production is enhanced by increasing amount of upwelling meltwater. Nevertheless, the plume process is not directly related to the intake of carbon from the atmosphere.”

Bowdoin Glacier is smaller than other rapidly retreating glaciers in Greenland, such as the Jakobshavn and Helheim glaciers. The team hopes to find out if the processes observed in Bowdoin Fjord resemble the situations in the fjords of larger glaciers.

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Roundup: Bowdoin Glacier, Floods, and Bacterial Populations

Speeding-up of the Bowdoin Glacier

From People Publications: “Glaciers are subject to sudden ice flow speed-up events in response to rapid increase of meltwater in the subglacial hydrological network after a prolonged warm period or the drainage of a supraglacial lake…. lasting a few hours, a period too short to be captured by satellite remote sensing. We used a cost-effective Vertical Take-Off and Landing and Unmanned Aerial Vehicle to monitor bi-daily the movements of Bowdoin Glacier. Our results show four distinct short-lived speed-up events, which were in phase with fluctuations of air temperature and meltwater plumes at the glacier snout, showing that recorded accelerations were triggered by an increase of buoyant forces in response to a surplus of subglacial meltwater.”

Read more speed-up events here.

Tongue of the Bowdoin Glacier (Source: ETH Zurich/Creative Commons).

Glacial Lake Outburst Floods at Imja Lake

From MDPI: “Glacial retreat causes the formation of glacier lakes with the potential of producing glacial lake outburst floods (GLOFs). Imja Lake in Nepal is considered at risk for a GLOF. Communities in the path of a potential Imja GLOF are implementing adaptation projects. We develop and demonstrate a decision-making methodology. The methodology is applied to assess benefits in Dingboche of lowering Imja Lake by 3, 10 and 20 m. The results show that the baseline case (no lake lowering) has the lowest expected cost because of low valuation of agricultural land and homes in the literature.”

Read more about Imja Lake here.

Imja Lake in the middle of the Himalayas of Nepal (Source: Kiril Rusev/Creative Commons).

Bacterial Populations of East Antarctic Glaciers

From Frontiers in Microbiology: “Glacial forelands are extremely sensitive to temperature changes and are therefore appropriate places to explore the development of microbial communities in response to climate-driven deglaciation. We investigated the bacterial communities that developed at the initial stage of deglaciation using space-for-time substitution in the foreland of an ice sheet in Larsemann Hills. Our results show that abundant bacterial communities were more sensitive to changing conditions in the early stages of deglaciation than rare community members.”

Learn more about the bacteria populations of East Antarctic glaciers here!

Mineral treasures of Larsemann Hills, Antartica (Source: National Science Foundation/Creative Commons).
 

 

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Using Kayaks and Drones to Explore Glaciers

Field study sounds cool: a group of scientists take boats out into untraveled waters on an important scientific mission, even witnessing extraordinary scenery like an iceberg calving event along the journey. However, the breathtaking beauty of such a trip can also come at a price, sometimes even human life!

“I like working in Alaska, but I face the difficulties of any ice or ocean research project,” said Erin Pettit, an associate professor at University of Alaska Fairbanks. Pettit finds it hard to find a reliable boat and captain for her trips, and too much ice in the fjord often limits how close she can get to the glaciers. The risks to her personal safety rise when she has to work on cold or rainy days.

A group of scientists are collecting data from Le Conte Glacier (source: Cal Dail/Flickr).

“It can be really dangerous in Alaska, so we send the kayaks out,” said June Marion, the principal engineer for a new study using remote-controlled kayaks to research Le Conte Glacier. The oceanic robotic kayaks are controlled by a laptop a few miles away, according to Marion.

“When the calving event happens and an iceberg falls onto the kayak, we do not need to sacrifice valuable human life,” she said. “More importantly, the kayak can go further into unexplored regions. We are more hopeful to collect data.”

Mechanical engineer June Marion works on the kayak’s engine assisted by her dad, Bobby Brown. Working on the rear kayak is robotics science students Nick McComb and Corwin Perren (source: Angela Denning / NOAA).

With a radio controller or a computer, the researchers navigate the kayak by clicking on points on a map, sending the kayak directly to the location for study. The engine can even be started using a computer program.

“There are always new technologies being used on glaciers,” said Pettit.

Guillaume Jouvet et al. figured out another way for scientists to avoid danger during field work. They used unmanned aerial vehicles (UAVs), also known as drones, to study calving of the Bowdoin Glacier in Greenland in 2015. They combined satellite images, UAV photogrammetry, and ice flow modeling, drawing important conclusions from the results.

With UAVs, researchers are able to obtain high-resolution orthoimages taken immediately before and after the initiation of a large fracture, including major calving events. In this way, Jouvet et al.’s study demonstrates that UAV photogrammetry and ice flow modeling can be a safer tool to study glaciers.

Measurement of surface temperature of a glacier using an unmanned aerial vehicle (UAV) (source: W. Immerzeel et al.).

This technology has also been successfully applied to monitor Himalayan glacier dynamics: the UAVs can be used over high-altitude, debris-covered glaciers, with images of glacier elevation and surface changes derived at very high resolutions, according to W. Immerzeel et al.. UAVs can be further revolutionized to develop current glacier monitoring methods.

Scientists like Marion and Pettit are excited to see these new technologies developed to study glaciers and save lives. They are hoping for more methods to achieve this goal.

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Roundup: Kayaks, Snow Machines and Drones

Roundup: Kayaks, Regrowing Glaciers, and the Bowdoin

 

Research Using Remote-Controlled Kayaks

From Alaska Public Media: “LeConte Glacier near Petersburg… [is] the southern-most tide water glacier in the northern hemisphere and scientists have been studying it to give them a better idea of glacial retreat and sea level rise around the world… to get close to the glacier, which is constantly calving, a team of scientists is relying on unmanned, remote controlled kayaks… these kayaks have been completely tweaked by Marion and an ocean robotics team from Oregon State University… The boats are customized with a keel, antennas, lights and boxes of computer chips and wires.”

Find out more about the kayaks and research here.

LeConte Glacier’s calving front (Source: Gomada / Creative Commons)

 

Regrowing Morteratsch Glacier with Artificial Snow

From New Scientist: “The idea is to create artificial snow and blow it over the Morteratsch glacier in Switzerland each summer, hoping it will protect the ice and eventually cause the glacier to regrow… The locals had been inspired by stories that white fleece coverings on a smaller glacier called Diavolezzafirn had helped it to grow by up to 8 metres in 10 years… Oerlemans says it would take 4000 snow machines to do the job, producing snow by mixing air blasts with water, which cools down through expansion to create ice crystals. The hope is that the water can be “recycled” from small lakes of meltwater alongside the glacier… But the costs… are immense.”

Find out more about how this works here.

Snow cannons like this could help regrow Morteratsch Glacier (Source: Calyponte / Creative Commons)

 

Drones Capture a Major Calving Event

From The Cryosphere: “A high-resolution displacement field is inferred from UAV orthoimages (geometrically corrected for uniform scale) taken immediately before and after the initiation of a large fracture, which induced a major calving event… Modelling results reveal (i) that the crack was more than half-thickness deep, filled with water and getting irreversibly deeper when it was captured by the UAV and (ii) that the crack initiated in an area of high horizontal shear caused by a local basal bump immediately behind the current calving front… Our study demonstrates that the combination of UAV photogrammetry and ice flow modelling is a promising tool to horizontally and vertically track the propagation of fractures responsible for large calving events.”

Find out more about the study here.

Drones are increasingly being used to study glaciers (Source: Creative Commons)
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