Dr Christina Riesselman, geologist, University of Otago, Dunedin
Three million years ago Earth was much as it is today – familiar continents, animals, and carbon dioxide levels. But temperatures were higher and sea levels were also about 20 metres higher. Today, a billion people live on land less than 20 metres above sea level, and carbon dioxide levels are rising.Working on the Antarctic ice shelf and at sea Dr Christina Riesselman collects sediment cores from hundreds of metres under the sea floor and reads the climate history of millennia past using the microscopic fossilised fish teeth and diatomic algae she finds in the cores.Christina will use her L'Oréal-UNESCO For Women in Science Fellowship to turn her focus to the end of the last Ice Age around 10,000 years ago. 2014 was the hottest year on record, but was it the hottest year since the end of the last ice age? Christina’s research could answer that question and help us understand and plan for the impact of our planet’s rapidly changing climate.
Christina is a geologist at the University of Otago in Dunedin.
Christina’s parents are both scientists and she was determined not to follow them. So she went to university intending to be a writer. But, the experiences of a Rocky Mountains childhood, visits to Yellowstone National Park, and a great geology lecturer combined to capture Christina’s interests.
From the University of Nebraska-Lincoln she went to the non-profit Joint Oceanographic Institutions in Washington DC, then Stanford, and the US Geological Survey, ending up in Otago in 2013 having been drawn south by a series of Antarctic expeditions.
In essence Christina is piecing together the climate record of past millennia. She does that with the help of ships like the JOIDES Resolution, one of the flagships of the International Ocean Discovery Program. The JOIDES Resolution is, for Christina, “Like a space shuttle for geoscientists.” It can lower a drill bit kilometres down under the Southern Ocean and then drill into the ocean floor and bring up sediment cores that hold the record of past climate going back millions of years.
Christina cracks these cores open to reveal the cycle of life and death in prehistoric Antarctica. The sediments contain the glass-like shells of diatoms, microscopic plants that form a large part of the plankton in the Southern Ocean. And these fossils can tell us much about the iciness, temperature, and chemistry of the oceans in which they grew.
“Sometimes I’ll crack open a core and there is a 3 cm layer representing a single year. I can see the retreat of the sea ice, the algae growing in spring and summer and then the return of the ice in winter,” says Christina. Other cores have taken her back to the time of the dinosaurs.
But her focus to date has been on sediment cores some three million years old. These are from an era when life on Earth was much as it is now with similar carbon dioxide levels to those in the atmosphere today as a result of human activity. But, there was one critical difference: temperatures were higher, the Antarctic ice sheets had retreated, and as a result the oceans were about 20 metres higher than they are today.
Christina will use her L’Oréal-UNESCO Fellowship to study more recent sediment cores that carry East Antarctica’s climate record of the past 11,000 years. This is a period of rapid climate change as the Earth came out of the last ice age and sea levels rose to their modern levels.
“What we’re learning about past climate will help us better understand the changes that we’re making to the planet right now, and help us plan for the future,” says Christina.
PhD (geological and environmental sciences), Stanford University, USA
Bachelor of Arts (English and geology), University of Nebraska-Lincoln, USA
Career highlights, awards, fellowships, grants
Korea Polar Research Institute sediment coring expedition (ANA05B), Ross Sea, Antarctica
Project leader for Ministry of Business, Innovation and Employment funded Past Antarctic Climate programme
Co-principal Investigator, New Zealand Antarctic Research Institute grant
Organiser and facilitator, Dual Careers in Academia panel and workshop for early career scientists, Goldschmidt2014, Sacramento, USA
Principal Investigator, Royal Society of New Zealand Marsden Fund, Windows onto warmer worlds: Sea ice, nutrient utilization, and primary production on the Wilkes Land margin, Antarctica
TRACERS modern process cruise (NBP13-02), Ross Sea, Antarctica
Invited contributor, A multiproxy approach to the reconstruction of Pliocene climate workshop, Barcelona, Spain
Invited presentation, Geological Society of Washington, Cosmos Club, Washington DC, USA
Mendenhall Postdoctoral Fellowship, U.S. Geological Survey
Invited presentation, International Symposium on the Antarctic Earth Sciences, Edinburgh, UK
Invited presentation, University School of Earth and Environment, Earth Surface Science Institute, Leeds, UK
Invited presentation, American Geophysical Union, San Francisco, USA