SIPERG Members

Dr. Alan Wanamaker — Professor and Principle Investigator

Welcome to the SIPERG. I am a broadly trained geoscientist who is interested in using geochemical and sclerochronological techniques to document (and better understand) changes in Earth’s climate and ecosystems through time. I particularly enjoy developing and using proxy archives to unravel past environments. We have several exciting research projects that are underway, so if you would like to know more about us, and our research group, please contact me.

Suzanne Ankerstjerne — Lab Manager

I am the lab manager for the Stable Isotope Laboratory in the department of Geological and Atmospheric Sciences. My duties include coordinating and scheduling activities within the lab and maintaining the resources necessary to complete quality stable isotope measurements. I enjoy working with students, Iowa State faculty, and other scientists to obtain high quality data.

Hannah Carroll — Ph.D. Candidate

I am a PhD student co-majoring in Ecology and Evolutionary Biology and Environmental Science. I am co-advised by Al Wanamaker and Lynn Clark. I received my B.Sc. in 2008 from the University of Washington, Tacoma, where I conducted research in marine larval ecology. My dissertation research focuses on multi-proxy explorations of plant community ecology, climate, and fire over the Holocene in the Midwestern United States.

Juan Carlos Romero Gelvez— PhD Student

Juan Carlos setting up the water collection system

I recently completed a MS in Geology at Iowa State University. Specifically, I developed a rainfall record for the last 50,000 years from the Colombian Andes using several stalagmites. My PhD research will involve high-resolution sampling of stalagmites to investigate El Nino Southern Oscillation (ENSO) dynamics during the Holocene.

Diana Thatcher — PhD Candidate

I am a PhD student at Iowa State University working with Dr. Alan Wanamaker. I recently completed an MS in Geology (2015) and I have a BS degree in Meteorology from ISU with a minor in Chemistry. My project involves studying speleothems from a cave in Portugal (behind me in this picture) to develop a decadal-scale paleoclimate record of hydroclimate and atmospheric variability during the late Holocene.

Nina Whitney — PhD

I recently successfully defended my PhD at Iowa State University in Geology and Environmental Science, working with Dr. Al Wanamaker. Previously, I completed an MS degree (2015) in Quaternary and Climate Studies at the University of Maine in the Climate Change Institute and a BA in Geology from Carleton College (2012). My PhD work involves studying and documenting the oceanographic evolution of the Gulf of Maine during recent millennia using the long-lived bivalve Arctica islandica and other proxy techniques. Specifically, my research uses nitrogen, oxygen and radiocarbon isotope proxies to document changing water properties in the Gulf of Maine over the last several centuries and infer changing ocean current dynamics. This work also leads me to look at how the Atlantic meridional overturning circulation (AMOC) has changed recently. For more information on my research and for a copy of my C.V., please visit

Current Undergraduate Researchers and Laboratory Assistants

Ian Searles


Karine Holmes

Grace Murphy (photo coming)



Graduate Students

Juan Carlos Romero Gelvez: MS Geology, July 2019 – “A 50 kyr rainfall record derived from Colombian stalagmites: insights on intertropical convergence zone dynamics and the role of ocean circulation.”

Jared Ballew: MS Geology 2018- “Refinement and utilization of the marine climate proxy Arctica islandica: An ideal replication strategy for stable isotope studies and an investigation into the shell growth and hydrographic variability of Georges Bank (Northwestern Atlantic).”

Madelyn Mette: PhD Geology and PhD Environmental Science 2017- Arctica islandica shell growth and geochemical records from northern Norway as North Atlantic marine climate proxies for the last millennium.”

Diana Thatcher: MS Geology and MS Environmental Science 2015 – “Developing a decadal-scale stalagmite record of hydroclimate and atmospheric variability for western Iberia (Portugal) during the Late Holocene.”

Erin Lower: MS Geology 2012 – “A high-resolution geochemical proxy record of radiocarbon and oxygen isotopes in the Gulf of Maine using Arctica islandica shell carbonate.”

Shelly Griffin: MS Geology 2012 – “Applying dendrochronology visual crossdating techniques to the marine bivalve Arctica islandica and assessing the utility of master growth chronologies as proxies for temperature and secondary productivity in the Gulf of Maine.”

Erin Beirne: MS Geology 2011 – “Pursuing a proxy for carbon cycling in the temperate North Atlantic: an investigation of the utility of Arctica islandica shell carbonate to millennial scale dissolved inorganic carbon reconstructions.”

Previous Undergraduate Researchers and Laboratory Assistants

Jessica Feenstra

Ron VanDenBroeke

Megan Hosford

Andrew Lane

Dana Korneisel

Hayley Nelson

Shaina Ives

Claire Gruver-Pandich

Jared Ballew

Jesse Matt

Katie Luzier

Aubrey Foulk

Alexis Gruber

Owen Tazelaar

Gabrielle Heidrich