Recent and ongoing projects
 
Interhemispheric Water-Mass Exchange at Intermediate Water Depth in the Atlantic Recorded by Nd Isotope Ratios
The clear difference in the εNd signature of North Atlantic and Southern Ocean water masses, makes εNd measured on fossil marine sediments, an ideal tool to constrain  changes in the northward extent of Antarctic Intermediate Water (AAIW) in the Atlantic. Two new εNd records from the mid-depth Tobago Basin (tropical W Atlantic) and Brazil margin (SW Atlantic) show abrupt εNd increases during the last deglaciation, suggesting enhanced northward penetration of AAIW. Most notably, AAIW presence in the tropical Atlantic was high at ~19ky and during Heinrich event 1 and the Younger Dryas. The latter mark episodes of reduced North Atlantic Deep Water formation, supporting a ‘seesaw’ relationship between AAIW northward extent and NADW formation. 
Proxies: Authigenic Nd isotope ratios.
Funding: Lamont-Doherty Postdoctoral Fellowship and ARCHES.
Mentors: S. Goldstein, S. Hemming.

Glacial Water Mass Geometry in the South Atlantic: Testing Neodymium Isotopes Versus Benthic Carbon Isotopes as Paleo-Water Mass Tracers
The study is designed to conduct a large-scale survey of the Holocene and LGM distribution of Nd isotopes in the South Atlantic, an area particularly sensitive to changes in the export flux of NADW. With respect to the quasi-conservative nature of Nd isotopes in the ocean, this will add critical complementary insight into past water mass geometry (as understood from benthic δ13C) and changes in relative mixing proportions of water masses. Moreover, it will promote the further development of a highly promising water mass tracer as paleoceanographic tool.
Proxies: Nd and Sr isotope ratios, benthic foraminiferal δ13C
Funding: NSF grant OCE-07-26575 (PI: K. Pahnke; co-PIs: S. Goldstein, S. Hemming).

Vertical εNd Distribution in the Western Tropical Atlantic During the Last Glacial Maximum and Holocene
This project was the focus of the senior thesis of Joseph Simonson, Columbia, 2008.
A depth transect of four sediment cores from Ceara Rise, North Atlantic, were analyzed for Nd isotopes in the Holocene (core-top) and last glacial maximum (LGM) time slices. The Holocene profile clearly mirrors the water-column structure of AAIW, underlain by NADW and AABW. The LGM profile shows a marked shift of eNd towards Southern Ocean values at depth, indicating increased northward penetration of AABW at that time. This is consistent with the current understanding of the water-mass geometry during the LGM. 
Proxies: Authigenic Nd and Sr isotope ratios.
Funding: LDEO Climate Center, NSF grant OCE-07-26575 (PI: K. Pahnke; co-PI: S. Goldstein).

GEOTRACES: International intercalibration of Nd isotopes and REEs
“GEOTRACES is an international study of the global marine biogeochemical cycles of trace elements and their isotopes. Its mission is to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions” (GEOTRACES Science Plan, http://geotraces.org).
Together with Tina van de Flierdt (Imperial College, London) I am coordinating the intercalibration of Nd isotopes and REE concentrations for the GEOTRACES program. We collected 20L and/or 0.5-2L of seawater each at two stations in the northwest Atlantic (BATS and Virginia slope) for 17 different laboratories worldwide for the intercalibration of Nd isotopes and/or REE concentrations. Each lab also received three particulate samples from BATS deep (4000m) and BATS surface (30m), and from the Virginia slope from 40m water depth. 
Additionally, we conducted a number of tests at both stations in surface and deep waters to compare different filter types and sizes for their performance and effect on the dissolved Nd and REE fractions. A depth profile at BATS will serve as GEOTRACES baseline profile for repeated reoccupation in the future. 
Parameters: Nd isotopes and REE concentrations in seawater and particulates.
Funding: NSF grant OCE-07-52402 (PI: R.F.Anderson; co-PIs: B.Moran, T.v.d.Flierdt, K.Pahnke, M.Q.Fleisher).

Hydrological Changes in the Panama Basin Across the Last Glacial Termination
Panama Basin, eastern tropical Pacific, core KNR176-32JPC (4.5ºN, 78ºW, 2200 mbsf).
Pahnke et al., Paleoceanography 2007.pdf
Proxies: Alkenone D/H ratios and alkenone unsaturation ratios (UK’37).
Funding: Comer Fellowship (Garry Comer Science and Education Foundation). 
Mentor: Julian P. Sachs.

Mid-Latitude Southern Hemisphere Sea Surface Temperature Changes
Chatham Rise, southwest Pacific, cores MD97-2120 (45ºS, 175ºE, 1210 mbsf), MD97-2121 (40ºS, 178ºE, 3014 mbsf). Cape Basin, southeast Atlantic, ODP Site 1089 (4ºS, 10ºE, 4621 mbsf).
Pahnke and Sachs, Paleoceanography 2006.pdf
Proxy: Alkenone unsaturation ratios (UK’37).
Funding: Comer Fellowship (Garry Comer Science and Education Foundation). 
Mentor: Julian P. Sachs.

Past Antarctic Intermediate Water Variability in the Southwest Pacific
Chatham Rise, southwest Pacific, core MD97-2120 (45ºS, 175ºE, 1210 mbsf). 
Pahnke and Zahn, Science 2005.pdf
Proxies: benthic foraminiferal (C. wuellerstorfi) δ13C, δ18O.
Funding: DAAD stipend (German Academic Exchange Service) and Leverhulme Trust, UK (PI: Rainer Zahn).

Millennial-Scale Changes in Surface Ocean Conditions in the SW Pacific Over the Past 340,000 Years
Chatham Rise, southwest Pacific, core MD97-2120 (45ºS, 175ºE, 1210 mbsf). 
Pahnke et al., Science 2003.pdf
Proxies: planktonic foraminiferal (G. bulloides) Mg/Ca, δ18O.
Funding: DAAD stipend (German Academic Exchange Service) and Leverhulme Trust, UK (PI: Rainer Zahn).















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