Daniel Murphy, Texas A&M University

Title: North Pacific intermediate water circulation over the last 60 kyr: Southern California margin

Relevant Expeditions: ODP Legs 146 and 167

Proposal Abstract: Over the last 60 kyr, the organic carbon content of California Margin sediments has varied significantly (6 to 12 wt%) on stadial to interstadial timescales, likely reflecting changes in the strength of the oxygen minimum zone. Two mechanisms have been proposed to explain these variations: 1) regional changes in sea-surface productivity influenced seafloor oxygen levels, and/or 2) the source of intermediate waters changed, with a more proximal, oxygen-rich North Pacific source during the stadials, and a more distal Southern Ocean source during the interstadials. For my Schlanger Ocean Drilling Fellowship research I will test potential causes of enhanced interstadial organic carbon accumulation by tracking changes in intermediate water-mass composition—as recorded at ODP sites 893 and 1017—across interstadials 8 to 14 (~37 to 52 kyr ago) using Nd isotopes from benthic foraminiferal calcite. My preliminary results using coeval fish debris indicate that benthic foraminifera reliably record seawater Nd values and indicate a Southern Ocean intermediate-water source during interstadials.  

Biography: Unlike many marine scientists, I did not grow up fascinated by the ocean.  In fact, I had never even seen the ocean until I attended Hawai’i Pacific University where I ended up earning my bachelor’s degree in marine biology. As a senior, I took geological oceanography as an elective and soon fell in love with paleoceanography. The questions it posed seemed bigger than those considered in marine biology—and more relevant given today’s changing climate. After completing my master’s degree at the University of California, Santa Barbara, I began my Ph.D. at Texas A&M University with Deborah Thomas as my advisor. Eventually, I hope to pursue a career in academia addressing questions from all time scales using the skill sets I am developing. The challenges presented to me by my research are almost as exciting as spending time with my wife Jonna and my daughter Autumn who was born in February 2007.