By: Carey Schafer, Web Content Developer, USF CMS
To be a geologist, you must reckon with time. The Earth is 4.54 billion years old. The average lifespan of an adult in the United States is 79 years. Two timescales that are fundamentally at odds with one another.
Antarctic marine geologists at the USF College of Marine Science live in a world of time incompatibilities. Drawn to past, yet living in the present, they work to merge these two worlds -- ultimately with the goal of improving the future.
Million-year-old mud. To someone like College of Marine Science PhD candidate, Imogen Browne, really old mud is synonymous with gold. Browne, who works with Associate Professor Amelia Shevenell, PhD, studies 17 to 14 million-year-old mud to be exact. This mud, recovered from the bottom of the Ross Sea, allows Browne to time travel.
In 2018, Browne and Shevenell took part in the International Ocean Discovery Program (IODP) Expedition 374 to the Ross Sea. Their goal was to recover sediment cores that would be used to piece together the climatic history of Antarctica, specifically the growth and decay of ice sheets and changes in Southern Ocean circulation through time.
They struck gold. While at sea, the international team of scientists from 12 countries, recovered hundreds of meters of sediment from below the sea floor, representing millions of years of climate history.
Browne is working with sediments deposited during the Miocene, a geologic epoch that extends from 23 to 5.3 million years ago. “The Miocene is interesting because it contains intervals of both warm and cold climates. The middle Miocene is particularly interesting, because it’s the most recent time in Earth’s history when atmospheric carbon dioxide was as high as it is now,” said Browne. “It’s also the last time we had global conditions much warmer than today, with ice sheets much smaller.”
In contrast to Browne, fellow Shevenell lab member and PhD candidate, Kara Vadman, works with relatively “young,” 0 to 16,000-year-old samples she and Shevenell collected in 2014 from the Sabrina Coast, East Antarctica. East Antarctica receives less attention than West Antarctica, because it is more remote and stable. The relative lack of attention drew Vadman to the project.
“The East Antarctic Ice Sheet is one of the largest unknowns in future sea-level rise scenarios,” said Vadman. “Our work will provide insight into how the ocean and ice sheets have behaved in this area since the last glaciation, approximately 25,000 years ago.”
Browne and Vadman work as detectives, using geochemical clues to piece together how and why Antarctica’s ice sheets have changed over time. In total, marine geologists from the College of Marine Science, including Browne and Vadman, have conducted research in over ten locations across Antarctica, with samples spanning nearly 55 million years.
There is a reason this million-year-old mud has been likened to gold - it’s hard to get. Scientists must not only travel to the bottom of the Earth, but also to the bottom of the ocean. Planning for Antarctic field research involves years of careful preparation, followed by months on a ship or in the field.
A single trip may represent a significant portion of a researcher’s life. Missed birthdays and holidays. In geologic time, it’s a blink of an eye.
Shevenell, who wrote the science proposal for the 2018 IODP Expedition to the Ross Sea, has had firsthand experience with planning these trips. Shevenell and a team of scientists submitted a pre-proposal to obtain sediment cores in the Ross Sea in 2007, wrote the full proposal during a 2012 workshop at the College of Marine Science, and got expedition approval in 2017. According to Shevenell, this timeline is relatively quick, as coring proposals go. Her newest IODP proposal, an expedition to the Sabrina Coast continental shelf to expand on data collected by Vadman and CMS alumnae and IODP Curator, Katy Smith, has been in the works for several years.
Once at sea, scientists must adjust to a 12-hour work schedule. For Browne, this meant sleeping until 8 pm, waking up, working out, and showering in time for an 11 pm breakfast before the beginning of her shift. “Day and night don’t have the same feeling in Antarctica,” said Browne, “since it never got dark while we were there.”
Ryan Venturelli, a PhD candidate who works with Associate Professor Brad Rosenheim, PhD, is no stranger to the time commitment that accompanies Antarctic research. Venturelli is part of the Subglacial Antarctic Lakes Scientific Access (SALSA) project, which brings together geologists, geophysicists, geochemists, and microbiologists to study Mercer Subglacial Lake, a lake hidden under 1100 meters of Antarctic ice.
To prepare for SALSA, Venturelli traveled to Antarctica a year in advance of the SALSA field season to decontaminate and set up their mobile field laboratory in a shipping container. Once cleaned and prepped, the lab was transported to the SALSA field site along the Antarctic Traverse -- the “highway” connecting McMurdo station to the South Pole.
The following year, Venturelli spent six weeks in Antarctica with the SALSA science team, three of them spent living in a tent at a field camp 600 miles away from the nearest research station. The SALSA scientists reached their field camp near the middle of December, making for an atypical, but memorable holiday season.
“On New Year’s Eve, we were collecting our first sediment cores, which was really cool and maybe a bit weird for New Year’s Eve,” said Venturelli. “But we made sure to celebrate with appetizers in the food tent and by dropping a giant tinfoil ball from the ceiling.”
In total, members of the Rosenheim and Shevenell labs have spent over 1,000 days doing Antarctic field work. This does not include the time spent on proposals, processing and analyzing samples, and writing papers.
“Before I was a geologist, a day, a week, a season, a year: those were the time marks I was thinking about,” said Venturelli. “Throughout the last decade of being a geology student, I’ve started to think about time on a much different scale: the breakup and collision of continents, mountain building and erosion, glacial-interglacial cycles, the evolution of life on earth.”
For most Floridians, traveling to the ice-covered landscape of Antarctica would be like walking on the moon. Distant and different.
Yet, those studying Antarctica would argue these landscapes are inextricably linked.
“Antarctica’s ice sheets contain 58 meters of sea level equivalent ice, of which about 24 meters is sensitive to ocean warming, said Shevenell. “Understanding where and how fast Antarctica’s ice sheets are melting is really important to Floridians, many of whom live on the coast and a majority of whom live within a meter or two of sea level.”
There is a phrase one is bound to hear if they were to step into a marine geology class: the present is the key to the past, and the past is a window into the future. The work done by both the Shevenell and Rosenheim groups, while grounded in the past, has implications for the future of our planet.
One of the biggest challenges is how to communicate those risks, which occur on timescales longer than the average human lifespan. Based on current rates of sea level rise, the Tampa-St. Petersburg metro area will experience 0.9 meters of sea level rise by 2100. It’s estimated this would result in the displacement of between 100,000-230,000 people. “Although geologists are used to thinking on long timescales,” said Vadman, “for most people, it doesn’t resonate when you tell them about a threat 80-years down the line.”