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To See Past Climate, Read Between the Clam's Lines

Field Notes
By Randall Hyman
Aug 27, 2014 11:46 PMNov 19, 2019 8:39 PM


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This is the second is a series of three posts from researchers' expedition to northern Norway. Read others in the series here.

Marine ecologists Rob Witbaard and Michael Carroll help Captain Thorleif Hanssen redeploy Witbaard's clam experiment. Fieldwork anywhere in the world is risky business, no less so here at the island of Ingøya off the north tip of Norway, where Arctic storms can blow up out of nowhere and prevent scientists from going to sea for days at a time. After arriving Monday evening in a wash of golden sunlight that poured like honey across the green tundra, our team of scientists has watched weather steadily worsen. It was a non-issue on land, where we battled wind and cold with layers of wool and Gore-Tex, but another story at sea, where waves and huge swells can toss you overboard into frigid waters. Despite three days of productive shoreline work, paleoclimatologist Al Wanamaker of Iowa State University has grown antsy waiting to sail far off shore. There sits the mother lode: Arctica islandica clams never before collected this far north nor this deep, at 71 degrees latitude and up to 600-foot depths. If Wanamaker scores, he’ll have a solid basis for tracking the climate impact of the northward-flowing Gulf Stream (North Atlantic Current), free of the influence of the freshwater runoff in coastal currents.

A Clam's Perspective

By reading the lines of annual growth rings on clam shells and measuring their carbon and oxygen isotopes, the team here is getting a lock on the strength of the North Atlantic Current over the past millennium as it entered the Barents Sea.

Artero and Witbaard enter data from wired clams in containers beside them. “There’s strong evidence for a connection between the amount of North Atlantic water entering the Arctic and the extent of sea ice,” says Wanamaker. “One intent of our study is to estimate the past behavior of the North Atlantic Current so that we can better understand the potential influence this system has on Arctic climate change.” However, the expedition’s captain, Norwegian Thorleif Hanssen, a burly man of few words, has wisely declined Wanamaker’s daily entreaties to ply deep waters, quietly shaking his head each evening with a single, “Not tomorrow.” Several days after our arrival, I realized how wise Hanssen had been as I accompanied marine ecologist Rob Witbaard aboard a fishing boat in sizeable post-storm swells that heaved our vessel back and forth. Witbaard and his PhD student Irene Ballesta Artero were there to redeploy the centerpiece of their research: an aluminum frame holding 28 clams, 16 of which are wired with electronic loggers tracking feeding and activity every minute. The frame also carries instruments that measure salinity, turbidity, light and temperature. A fluorescence sensor detects the abundance of phytoplankton, or clam food.

Irene Ballesta Artero pours dye into study clams' containers. The scientists had collected the frame from these same waters just two days before and downloaded all the data, before bathing the clams in a non-toxic calcein dye for 24 hours to time-stamp the shells with a thin fluorescent green growth line. They’ll use that marker to determine how much the clams have grown when they revisit them next year. “I’m looking at this project from the point of view of the clam,” said Witbaard, “trying to understand the environment and its consequences for shell growth.” By focusing on seasonal marine changes, especially the springtime bloom of phytoplankton, he and Artero are pinpointing the minute factors that trigger activity and growth. This is key to Wanamaker making increasingly accurate conclusions about the variable widths of annual growth increments and the interplay with climate change. As the 28 clams sank back into the sea, Artero gazed over our boat’s gunwales and murmured with a tinge of nostalgia, “Goodbye until next year.”

Beaches Above Water

The next day, winds subsided and seas grew calm. Wanamaker, his grad student Maddie Mette, and marine ecologist Michael Carroll set sail for deep water while another team dredged clams in shallow Sanden Bay. I, however, opted for dry land, joining geologist Mike Retelle who is working to reconstruct sea level changes since the last ice age by tagging the stepped terraces along the present shoreline. Dating each raised beach based upon the shells within it, Retelle can link living and dead clams collected on the modern beach to those above sea level, and extend the climate-change timeline beyond Wanamaker’s initial goal of a single millennium.

Geologist Mike Retelle hikes with an assistant atop a series of ancient raised beaches seen as terraces. “Here it is,” Retelle says as we work our way up from the shore and top a spongy tundra terrace filled with a small lake. Our path is strewn with orange-yellow cloudberries, and I pause to pop a few in my mouth and relish the sweet, tangy taste of an Arctic summer. “See the rounded gravel and rocks everywhere?” says Retelle. “This was once a beach. My guess is it’s about 6,000 years old.” Fifteen thousand years ago, as the last ice sheets began to recede from northern Scandinavia and the region shrugged off their frozen burden, land began rising, leaving these shoreline terraces. Once Retelle knows the ages of the terraces, he will be able to target sampling sites for clams of various ages, allowing Wanamaker to reconstruct climate change and ocean currents even farther back.

Treasure Trove of Clams

At the end of the day, we hike across a sandy field that is completely carpeted with Arctica islandica shells. This remarkable site is the genesis of the team’s entire project on Ingøya.

A vast field of Arctica islandica at Sanden Bay. Marine ecologist Michael Carroll described his “aha” moment to me a few days ago as we dredged for clams. “I first came here in 2000 when drilling was getting started in the Barents Sea,” Carroll explained. “At Sanden Bay I looked down and realized I had been walking on shells for the last 300 meters. It was an old seabed…It all clicked in my head that this was just a dynamite place.” No one had ever documented Arctica islandica this far north, and the treasure trove was completely unknown in the scientific community. While Retelle and I tracked land-based geology, Wanamaker went for the biggest treasure of all: deep-water clams. With seas calm and gorgeous weather returning to this magical island at the northern tip of Norway and Arctica islandica’s range, I’ll report on the last days of the team’s research week in the third and final blog of this series. All images by Randall Hyman

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