Nicolás Young (LDEO), Jason Briner (UB) and an assortment of fellow scientists and graduate students are gearing up to spend a third summer camping along the Greenland ice margin. As part of an ambitious multi-institutional and cross-disciplinary project, NSF-funded Snow on Ice, Young and Briner are collecting lake sediment, rock, water and plant samples that will be used to tease apart linkages between reductions in sea ice on the Arctic Ocean, atmospheric uptake through increased evaporation from the exposed ocean surface and changes in snowfall on the Greenland Ice Sheet. The fieldwork will be centered in southwest Greenland where climate sensitivity during past interglacials was the greatest. The resulting data will be combined with new isotopic ice core work (UW) and updated subglacial topography (UCI), for delivery to two sets of modelers on the project team (UM and NASA JPL) to feed into a set of nested models. Canada’s Geotop and Denmark’s GEUS fill out the partner list.
Explore the photo essay below and read more below to learn about the exciting work of the Snow on Ice Project.
Traveling to remote study sites means loading people and gear into a helicopter. This Sikorsky is delivering the science team and their equipment right up to the edge of the ice. Some more remote campsites, with their proximity to the ice, are locations where the pilots have not previously ventured. Once the helicopter is unloaded, the co-pilot brings out a small crate packed with carafes of coffee and tea to share before they depart, bringing an odd bit of ritual to a very untouched backdrop. Photo: Margie Turrin
After setting up camp, the first order of business is to get out onto the lake in a small zodiac and collect depth measurements, creating a benthic map. A handheld sonar device is mounted on the zodiac and a survey of the lake undertaken. A map is created with the colors coming to life the screen as the boat moves back and forth across the lake. With the map as a guide, animated discussions occur about the best potential coring locations. With a limit on the number of core sleeves for the field season, each location is carefully selected. Sites are chosen to collect the lake sediment inflow, and yet located where inflow is not so high it will exceed the ability of the core sleeve to hold a complete record of events. Photo: Margie Turrin
The coring setup involves a zodiac acting as a small tugboat pulling the coring platform behind it as it pulls it into position. The coring platform is a pontoon with a wooden platform workspace and a large A-frame in the center for suspension of the piston coring mechanism. The core design is referred to as a “Bufforado” for its Buffalo and Colorado origin. It operates efficiently and with easily replaceable parts—a new wrench here, a new strap there and it is set to go. Anchors to hold the pontoon in place during deployment are local rocks wrapped with nylon cable. All in all, it is simple but effective. Here Jason Briner navigates the zodiac and Ole Bennike and Nicolás Young prepare to core. Note the gray colored water courtesy of the glacial till that flows into this pro-glacial lake. Photo: Margie Turrin
Lakes included in the field study were selected along the edges of the ice with drainage basins extending back beneath the present day Greenland Ice Sheet. This provides a continuous sediment record from silt-rich glacial sediments collecting under ice cover to organic rich non glacial sediments called gyttja when the ice sheet retreats out of the drainage basin. This lake sits right along the edge of the ice sheet and clearly extends back under the ice. Visual examination is not the main tool used for lake selection, instead, recently updated bed topography mapping using radar to image through the ice to the bed below was used to support lake selection. Photo: Nicolas Young
A series of ‘pearl drop’ lakes extends from the ice edge, each connected to the next, providing a continuous line of ice sheet drainage collecting and carrying sediment as the water flows. The lake closest to the ice will receive too much sediment to sample. Careful planning is needed to ensure the right balance of lake exposure and historic ice cover. Photo: Nicolas Young
When the weather was too windy to core on the lake, scouting was undertaken for the best glacial erratic locations. Here Nicolás Young takes stock of the area, hiking up the ridgeline to look for locations to collect rock samples for exposure dating. Photo: Margie Turrin
As the Greenland ice moved over the landscape it reworked the surface, entraining, pushing and repositioning rocks as it traveled, leaving behind large boulders, or glacial erratics. These rocks appear across the bedrock, dotting the surface just where they were dropped and providing a clock timed to their moment of placement. As the rock is exposed to the atmosphere, it is bombarded by cosmic rays streaming in from all directions. These rays send protons into the rock, causing it to form cosmic nuclides, the isotopes beryllium-10 and aluminum-26, which can be dated to determine how long the rock has been exposed, and by proxy, the time of ice sheet retreat. Perched erratics can be good for exposure as long as they haven’t been tipped or sections plucked out or eroded. Photo: Nicolas Young
Nicolás Young collects a surface rock sample from a glacial erratic at camp site JB2. Erratics sitting unshielded on the Greenland bedrock are selected for sampling. Using a multi-cosmogenic technique, isotopes beryllium-10 (half life of 1.39 Ma) and Carbon-14 (half life of 5,730 years) are used in tandem to calculate the time of rock exposure and thus when the Greenland Ice sheet retreated from this position. Photo: Margie Turrin
Collecting field samples has an established protocol. Rock samples are carefully bagged and labeled, compass locations recorded, photographs taken of the location and recorded with the sample’s unique ID for future reference. Photo: Nicolas Young
Nicolás Young and Ole Bennike hike up to the ridgeline to look out over the ice sheet and the wider drainage area. Along the left edge they noted a moraine that appears to have been deposited during the Little Ice Age (~1400-1850). In this area the moraine is close to the present day ice extent, but this is not true for all of Greenland. Ice velocity and underlying bed topography are the biggest drivers of ice change. In this region where it is not terribly steep and the ice velocity is not high, we still see the moraine and the ice side by side. Photo: Margie Turrin
At our first campsite, JB1, the terrain was steep, rocky and extremely windy. Arctic hare blended in to the rocks and caribou roamed the area, appearing out of nowhere to survey the region and then move off. The caribou were majestic with their mount of horns outlined against the skyline. Photo: Margie Turrin
Our camp was located along the ice margin where the Greenland Ice Sheet edge transitioned into the surrounding terrain. Heidi Roop (l) and Michele Koppes (r) look over the ice from the hilltop. A hike onto the ice sheet showed groups of erratics pushed into a line along what was once the ice edge, small rivers of meltwater cutting through the ice surface, and even a moulin where water dropped swiftly down into the ice sheet from a weakness that had been forced open in the ice. Photo: Nicolas Young
Ole Bennike from GEUS, Denmark stops to collect a s surface water samples from a small isolated ponds in the sampling area. Pond water is collected to use the water isotopic signature to determine water residence time. If the water is fully meteoric in origin, a linear relationship will exist between hydrogen and oxygen-18. In this part of Greenland the summers can be very dry leading to evaporation from the lakes, affecting the oxygen isotope ratio and altering the standard trend line. Photo: Margie Turrin
This caribou antler is resting in the short scrubby plant material covering much of the area in our camp site, material that will be collected for biomarker analysis. The plant with the small rounded leaves with round toothed edges is Betula nana (dwarf birch). Plants use oils to form a waxy protective coating which they build from hydrocarbon chains. The different hydrocarbon chains—shorter carbon chains (C 22-C 24) for aquatic plants and longer carbon chains (C 28-C 30) for terrestrial plants—can be analyzed to look at past precipitation. This is then used to build a Holocene climate reconstruction. Photo: Margie Turrin
Large fields of cottongrass Eriophorum sp. covered the region of our second campsite jB2. This site was further south than the first campsite, with musk ox and caribou wandering the landscape and loons calling regularly from the lake. Cottongrass was collected as part of the leaf wax isotopic study. Photo: Margie Turrin
At camp JB2, a series of lakes separated our campsite from the edge of the ice sheet. The water was an extraordinary aquamarine, colored with a milky tint from the glacial till. Here the coring team is motoring to a site to collect their first core from this lake. Photo: Margie Turrin
This full length lake cores has been split for a visual description prior to returning to the lab for a more comprehensive analysis. It shows a clear layering in the sediment. At the front of the image wet grey glacially sourced sediments are seen in the core. These eroded minerogenic layers would have been collected when the area was ice covered, and the glacier was grinding back and forth over the bedrock creating ‘glacial flour’. Just above that core is a series of very distinctively colored and textured layers of organic rich, non-glacial sediments, that would have entered the lake when the ice sheet had retreated leaving the lake uncovered. Towards the top of the photo we see a return to glacial flour or minerogenic sediments. The core layers represent a time series in the history of the ice sheet. Time moves from an ice covered cold climate to a warmer time when the ice sheet shrank leaving the lake exposed, back to a cooling period when the ice re-expanded to cover the lake. Photo: Nicolas Young
The winds next to the ice sheet rise up quickly and with an intensity that can be surprising. Called katabatic winds, they push down from the ice sheet into the lower valleys. Around the edges of the ice there are wide areas of water-deposited sediments that are whipped up by the wind and dumped into the lake. As they swirl in the air, they work like sandpaper grinding against the rocks, smoothing their surface. The first campsite was nicknamed “Ventifact Valley,” ventifacts for wind chiseled rocks. Here you can see the wind whipping the dust around our tent. Photo: Margie Turrin
The ice sheet has worked over the landscape in the past but in the present day there is ground cover, flowering plants, blueberry and crowberry bushes, and plenty of musk ox and caribou grazing on the plants. In every direction, ridgelines are visible and lower rolling hilltops in front. In several areas, wide U-shaped openings tell the story of the ice sheet having worn its way through the rock when it extended further than it does today. Photo: Margie Turrin
From the top of the ridgeline, the far reaches of the ice sheet are visible, trailing off into the clouds that blend with the white coloring. One lake in a series of drainage lakes sits in the center of our view and in the foreground are rocks scattered on the hilltop, left by the ice as it retreated back to its present position. The scenery is rich, and at the same time somewhat austere. Photo: Margie Turrin
The project goal is to look at the last 8000 years in Western Greenland, spanning back into the last Thermal Maximum when temperatures were approximated at 1-2°C warmer than today and the ice sheet was smaller. It is difficult to constrain the dimensions of an ice sheet that is smaller than present as the traditional markers that are used for evidence are covered over but we will tackle it with the multiple instrument approach described above. The data will be used as a proxy for what might happen in Greenland’s future, addressing with increased certainty whether reductions in Arctic sea ice in the past triggered a feedback loop that caused increased precipitation falling as snow, and resulted in stabilizing the Greenland ice Sheet even in a warming climate.
For more on this project see the Snow On Ice website.
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