Gregory A. de Wet

PhD Candidate

Department of Geosciences, University of Massachusetts, Amherst

My research focuses broadly on paleoclimatology and paleolimnology with a particular interest in the Arctic region. I enjoy the combination of field work, meaningful science, and societal relevance that paleoclimatology allows for as a field of study.

I received a Bachelors of Science degree from Bates College in 2011, where I completed an Honors Thesis working with Dr. Mike Retelle on catchment dynamics and climate history recorded in proglacial Lake Linne in Svalbard. I completed my Masters of Science degree at the University of Massachusetts in the spring of 2013, working with Dr. Raymond Bradley to create a paleoclimate record from Nanerersarpik Lake in SE Greenland spanning the Holocene.

My current research involves the use of organic biomarkers to reconstruct paleoenvironments from lake sediments. During the first part of my PhD I worked with Profs. Julie Brigham-Grette and Isla Castañeda on sediments from Lake El’gygytgyn in Siberia. “Lake E” was created 3.6 million years ago by a meteorite impact and contains the longest known continuous terrestrial sediment record from the Arctic. We used bacterial membrane lipids called branched glycerol dialkyl glycerol tetraethers (brGDGTs) to reconstruct temperatures across “super-interglacial” Marine Isotope Stage 31 (~1.7 million years ago). Our record (published in EPSL), the highest resolution temperature reconstruction from this interval to date, suggests that the interglacial may have lasted much longer than previously thought, with warming persisting during intervals of reduced local summer insolation.

In the latter stages of my PhD here at UMass I have been working with Drs. Bradley and Castañeda (along with Dr. Vincent Bichet and colleagues at the University of Franche Comté in Besaçon, France) on Norse sites in the southwestern part of Greenland. Here we are using two different suites of biomarkers; brGDGTs, alkenones, leaf waxes, etc. to reconstruct paleoclimate and fecal sterols, PAHs (produced by biomass burning), and other polar compounds to reconstruct human presence in the landscape. The goal of this research is to produce paired records from the same sedimentary archive to understand how human populations may have responded to changing climate.

We are also applying this technique to lake sediments recovered from the Faroe Islands, where questions remain regarding the when the first people actually arrived in the archipelago. In addition to the organic molecules that are indicative of human presence in the landscape we also plan to look for ancient DNA from humans and grazing mammals to definitively determine when people first arrived.

In addition to the organic geochemical techniques described above, I have also been applying more traditional proxies to lake sediment archives. During my time at the University of Bergen on a Fulbright Research Scholarship (2015) I worked with Dr. Jostein Bakke and colleagues to reconstruct the glacial history of Gjøavatnet in NW Svalbard. This work is currently under review in Quaternary Science Reviews.

I plan to defend my PhD in the Spring of 2017 and am actively pursuing both post-doc and teaching opportunities with the goal of becoming a college professor.