Reconstructing the Arctic’s Past for Clues to Its Future

A busy day in the field this spring. Scientists core for sediments they will use to reconstruct the Arctic’s past in the Brooks Range in northern Alaska. Photo: Jason Briner This year, geoscientists Jason Briner at the State University of New York at Buffalo, and Darrell Kaufman at Northern Arizona University, are continuing their investigation into lake sediments in the Brooks Range, in northern Alaska, to reconstruct climate and glacial changes that occurred in the Arctic stretching back 30,000 years ago.

Their collaborative project, Resolving centennial- to millennial-scale trends in glacier extent and lake sedimentation in the Brooks Range, is supported by the National Science Foundation.

We checked in with the geologists and David Fortin, a post-doctorate researcher with Kaufman, to learn about this year’s field missions and why this research is important.

Field Notes: What can you learn from reconstructing climate and glacial changes that occurred in the Artic so many years ago?

Jason Briner: Reconstructing changes in glaciers over time informs our understanding of how glaciers respond to climate. As geologists we study how glaciers have responded to past intervals of climate change. This research lets us look at a period of history when the earth was warmer than it is today and see what affect it had on glaciers. We can also study how glaciers responded to periods of rapid climate change.

An aerial view of the study areas. Photo: Jason Briner

Field Notes: Why Alaska?

Jason Briner: Very little is known from about this region.  When combined with records of glacier change from elsewhere, our new data will inform us about the spatial pattern of climate change throughout the Arctic.

Field Notes: How do you reconstruct what the Brooks Range might have looked like up to 30,000 years ago?

Jason Briner: There are two main ways. Last summer, we worked up in the mountainous parts of the Brooks Range to study the deposits that the glaciers left behind, like the boulders and moraines.

We combine what we learn from these site visits with aerial photographs to find these traces of where glaciers were in the past. Then we take samples to determine when these features were created.

When all the pieces are in place, we assemble a history of past glacier change (For more background on an earlier field mission in to the Brooks Range, check out some of our previous coverage of this project.)

The second way—what we did in April and May of this year—is to analyze sediment layers from lakes that exist down valley of glaciers. These layers tell us how glaciers grew and shrank in the past.

Field Notes: Can you elaborate?

Jason Briner: Glaciers produce a lot of sediment, which they deposit into rivers. Those rivers carry the sediment down mountain valleys and out to the sea. In valleys with lakes, some of these glacier-sediments become trapped in lake basins.

So, at the bottom of a lake there is a pile of layered sediment. And within all those layers of sediment is a history of how the glaciers changed through time.

We obtain cores of these sediments and analyze them in our labs to reconstruct glacier and climate changes.

Field Notes: Where did you collect samples this spring?

Darrell Kaufman: Our study lakes are located along the northern front of the central Brooks Range where Pleistocene mountain glaciers left massive deposits that now enclose lake basins. We took sediment cores from three lakes—Shainin Lake (about 70 km southwest of the Toolik Field Station); Shainin Pond (just 400 m from Shainin Lake); and Cascade Lake (145 km west of Shainin).

The team’s temporary home and shelter from the harsh conditions in the Brooks Range. Photo: Jason Briner

Field Notes: Describe a typical day in the field.

David Fortin: We usually got up at 7 am and started planning the daily operations over a good breakfast and strong coffee. By 8 am all of the gear was packed in the sled at the back of the snowmobile on its way to the first coring site of the day. The usual routine would be:

1. Shovel a 4m x 4m area to the ice surface.

2. Auger one or multiple holes in the ice, cut in between the holes with the ice saw.

3. Install the coring tripod and start the coring operation

4. Retrieve the core, cut in the cores 1.5-meter sections; label and bring the cores back to the camp.

By then it usually was lunchtime, and we would discuss the next operation in the kitchen tent. After one or two more cores in the afternoon, we would have dinner around 7 pm, clean up the gear, recharge the batteries and crawl into our sleep tents. Most evening, we were back in our sleeping bags around 9pm.

Field Notes: How were the weather conditions this spring?

David Fortin: We experienced a wide range of working conditions, from near perfect weather, i.e. a few degrees below freezing point with a nice clear sky, to total blizzard with low visibility and rapid snow accumulation.

There was close to two feet of snow accumulation over a period of 24 hours at Shainin Lake! For a few days, temperatures dropped below 0°F early in the morning, making our work with open water fairly difficult; the propane torch became one of our most precious allies.

Field Notes: What’s next for this project?

Jason Briner: We have one more field season planned for the end of this summer. In the spring, we deployed some sampling equipment—called an incremental sediment sampler--in the lake to collect sediment samples throughout the late spring and summer.  Our fieldwork later this summer is to recover the samples and equipment.