December 17, 2020

Adventures in Climate Research

UMass Amherst geoscientists uncover critical new evidence of ocean warming

In the high reaches of the Canadian Arctic, conducting climate research for UMass Amherst, postdoctoral researcher Francois Lapointe and his Inuit guide were chased by a muskox. Eluding the huge creature, Lapointe returned to UMass with important evidence of unprecedented warming of the Atlantic Ocean.

A team led by Lapointe and University Distinguished Professor Raymond Bradley in the Climate System Research Center of the University of Massachusetts Amherst and Pierre Francus at University of Québec-INRS analyzed sediments gathered from the bottom of Sawtooth Lake on remote Ellesmere Island. The sediments provide a record of the Atlantic temperatures there as long as 2,900 years ago and show that the warmest interval over this period has been in the past 10 years.

“It’s been ridiculously warm,” says Lapointe, who has conducted field work in this region over the past 10 years. “It is not what it used to be; this is a new normal.”

Conducting climate research in the High Arctic is demanding. To go to the Canadian Arctic, a small team of scientists, including Lapointe, flew to Iqaluit, the capital of the Canadian territory of Nunavut, and from there to the Polar Continental Shelf Program, a polar research station in Resolute Bay. From Resolute Bay, they flew to Ellesmere Island in a Twin Otter plane equipped with skis. They undertook the trip in April, when temperatures average from 0 to -10 degrees Fahrenheit and the ice on the lake is thick enough to support a plane.

The research team camped for several days on the ice, eating lots of pasta and some dehydrated meals. “You have to bring extra food, because you never know when the plane will be able to return due to the weather,” Lapointe explains.

Francois Lapointe holds a thin section of sediment layers from Sawtooth Lake.

To gather dozens of sediment cores, the researchers drilled through two to three meters of ice. Once drilled, they used a coring system to collect the precious cores. They then placed the cores in a large heated tent to prevent freezing while they waited for the Twin Otter. The cores were tightly placed in a wooden case to secure them for the trip back to INRS-Quebec and the Department of Geosciences at UMass Amherst, an international leader in the study of climate systems.

The hard-won samples were analyzed in INRS-Quebec and in the Morrill Science Center, they revealed information critical to deeper understanding of climate change. The sediments from the lake contain titanium left over from centuries of rock weathering. By measuring the titanium concentration in the layers of sediment, scientists were able to determine relative temperature and atmospheric pressure over time. Because of the lack of atmospheric and temperature information in this remote region, Lapointe used reanalysis data that combines observations made in the past with today’s weather model. The new analysis revealed that titanium concentration can consistently map the Atlantic Multidecadal Variability, a large-scale Atlantic sea surface temperature phenomenon.  

The newly extended record shows that the coldest temperatures were between about 1400-1600 AD, and the warmest interval occurred during just the past decade. The research team’s study was published in October in Proceedings of the National Academy of Sciences.

The research is important because it correlates with findings from sediment records from other parts of the Atlantic Ocean, ranging from north of Iceland to offshore Venezuela. “This gives us greater confidence in our findings,” Lapointe says.

“The pace of the warming for the past 10 years is like nothing in the paleo record,” he says. “This has many implications, including the fact that we just witnessed the most active Atlantic hurricane season ever recorded.”

Bradley adds, “The surface waters of the Atlantic have been consistently warm since about 1995. We don’t know if conditions will shift towards a cooler phase any time soon, which would give some relief for the accelerated Arctic warming. But if the Atlantic warming continues, atmospheric conditions favoring more severe melting of Canadian Arctic ice caps and the Greenland ice sheet can be expected in the coming decades.”

Lapointe concludes: “Scientists don’t know much about Arctic climate because weather stations have only been recording for 50 years or so, and they are sparsely distributed out there. As such, these sediment archives really allow us a better understanding of the Arctic climate system and may even uncover unsuspected findings.”