Maureen Raymo and Gisela Winckler are co-chief scientists for two different International Ocean Discovery Program expeditions aboard the JOIDES Resolution.
Maureen Raymo and Gisela Winckler, Lamont-Doherty Earth Observatory scientists studying climate change, are leading two different expeditions to regions of the Southern Ocean in spring 2019.
Both scientists will be participating in International Ocean Discovery Program (IODP) expeditions aboard the JOIDES Resolution. From March 20 to May 20, Raymo, a paleoceanographer and director of the Lamont Core Repository, is one of two co-chief scientists on the ship; the second is Michael Weber, a paleoclimatologist at the University of Bonn.
Winckler, a Lamont geochemist and Center for Climate and Life Fellow, is a co-chief scientist on the expedition immediately after Raymo’s. Winckler and her co-chief scientist, Frank Lamy, a marine geologist at the Alfred Wegener Institute for Polar and Marine Research, will sail on the JOIDES Resolution from May 20 to July 20.
Several other Lamont scientists are also participating in these expeditions. Sidney Hemming, a geologist and chair of the Columbia Department of Earth and Environmental Sciences, is sailing with Raymo. Julia Gottschalk and Jennifer Middleton, both postdocs, are participants on the expedition co-led by Winckler.
Iceberg Alley and Subantarctic Ice and Ocean Dynamics
The scientists on Raymo’s expedition are investigating how Antarctica’s ice sheets responded to changes in atmospheric carbon dioxide in the past and the impact of these changes on global sea level.
After years of planning, Raymo and her colleagues determined that a region of the Scotia Sea, east of the Antarctic Peninsula, is the ideal location to monitor the long-term history of icebergs that broke off the Antarctic Ice Sheet. They’ll visit six different sites in an area near the Drake Passage known as “Iceberg Alley” and collect sediment cores at each site that are about five inches in diameter and up to a few hundred meters to a kilometer long.
A sediment core is composed of organisms that lived and died in the surface ocean, as well as dust that blows into the ocean, or silt, sand, and mud dropped by icebergs, all of which falls to the bottom and accumulates layer by layer over millions of years.
Ships like the JOIDES Resolution are equipped to drill into the ocean floor and collect cores of this material; analyses of the sediments can reveal information about Earth’s climate history.
Raymo and her colleagues hope the cores they collect will contain seafloor sediments that date back as far as 20 million years, which would allow them to derive a 20 million-year history of Antarctic ice sheet behavior.
“Where we’re going, we’re going to see everything that was dropped by icebergs—the material they scraped off Antarctica—as they moved north away from the continent, hit warmer water, and began to melt,” said Raymo. “By matching the geochemical fingerprint of the material dropped by the icebergs to the geology of the bedrock of Antarctica, we hope to be able trace back through time where the icebergs were coming from, when, and how many there were.”
Scientists know that ice sheets are melting and accelerating the rate of sea level rise, but how much sea levels will rise in the future isn’t well understood, in part due to uncertainties in climate models. But by studying a period in the past when global temperatures were two degrees Celsius warmer than in pre-industrial times, scientists can try to determine how Earth’s climate responded to past changes in atmospheric carbon dioxide, and what sea levels and the state of the Antarctic polar ice cap were like during this time period. Scientists can then use this information to make better projections of how much and how fast future sea levels will rise, and how this will impact society.
Raymo and her colleagues also want to find out if there were certain climate thresholds or tipping points in the past where there was some degree point of warming that caused the stability of the ice sheets to change dramatically.
“If we could document that,” Raymo said. “We could say, ‘look, if the planet warms by more than this amount, we will likely be in serious trouble.’ Theoretically, that kind of information could be gleaned from in-depth knowledge of the past climate history of Antarctica.”
Although the Southern Ocean can be a difficult place to work due to its location, extreme weather conditions, and need to navigate around icebergs, Raymo is excited about the adventure.
“It’s a very pure experience—you’re doing science day in day out for 60 days with 30 smart scientists and technicians in beautiful state-of-the-art labs. And we all have this shared sense of mission and purpose and excitement about everything we’re discovering. Every day brings a new surprise.”
Dynamics of the Pacific Antarctic Circumpolar Current
For Gisela Winckler, her IODP expedition is the fulfillment of a professional dream. “I’m thrilled to be the co-chief scientist on this cruise,” said Winckler. “It’s a once-in-a-lifetime experience.”
She and her colleagues will sail on the JOIDES Resolution from Punta Arenas, Chile to explore the Pacific sector of the Southern Ocean, one of the stormiest and windiest parts of the global ocean. The science team will collect sediment cores from seven different locations at the Chilean margin and in the central South Pacific, one of the most remote places on Earth.
The Southern Ocean helps control how much carbon dioxide is in Earth’s atmosphere, so it plays a vital role in the global climate system, its variability, and how it responds to climate change. Scientists know that the Southern Ocean is changing rapidly due to warming temperatures, but many of its basic processes are still not well understood because it’s so remote.
The expedition is focused on the Antarctic Circumpolar Current (ACC), the largest and fastest current on the planet, which flows around Antarctica and connects the Atlantic, Pacific, and Indian Oceans, and therefore plays a critical role in global ocean circulation and climate.
The scientists on Winckler’s expedition hope to collect sediment cores that date back at least five million years and perhaps as far as 10 million years. By studying different grain sizes and the ratio between the coarse and fine material in the sediments, scientists can determine the speed of the ACC. This and other data will enable them to understand how the Southern Ocean system responded to past climate change, and how the speed of the ACC has changed over time.
“One of the big questions scientists still have is how atmospheric carbon dioxide changed in the past,” said Winckler. “The Southern Ocean played an important role in those changes. We’ll reconstruct what the ocean looked like in past intervals of warmth, when global temperatures were two or three degrees Celsius higher than today, and during cooler climates and what the processes were by which it exchanged carbon dioxide with the atmosphere. We don’t have any record of the feedbacks between ocean, atmosphere and the Antarctic ice sheet for the entire South Pacific—it’s uncharted territory.”
Winckler’s team will also examine the dust contained in the sediment cores. Dust carries iron, which “fertilizes” the ocean by providing nutrients essential for the growth of marine phytoplankton. Today in the Southern Ocean, not all the major nutrients in the surface ocean are consumed, mainly due to a lack of iron. But during glacial periods, dust delivered iron, stimulating phytoplankton growth. This process draws carbon dioxide from the atmosphere, through photosynthesis, into the ocean and impacts the carbon cycle.
The results of this research will improve understanding of the ACC and shed light on the role of the Southern Ocean in the global carbon cycle. Winckler says they’ll also be used to improve climate models.
“That’s where the paleoclimate record can be tremendously helpful,” she said. “The information we learn will be fed into the models. That back and forth between models and observations will eventually get us to a better understanding of future scenarios.”
As co-chief scientist, Winckler feels excitement and a great sense of responsibility for ensuring that the expedition is a success so that scientists can answer critical questions about how our planet is changing.
“We have to make sure we put all these different pieces of information together to get the most out of the sediment cores,” she said. “I truly think the questions we are trying to answer are so important that we must get this work done as fast as we can.”
— Renee Cho is a freelance writer who also contributes to the Earth Institute’s State of the Planet