Professor Alexander Piotrowski

Reconstructing the Ocean-Climate Link with Geochemical Tracers

The primary focus of my research is to understand the link between ocean circulation and climate over recent earth history.  The global ocean overturning is an important component of the earth’s climate system because the deep ocean hosts a large reservoir of carbon dioxide that exchanges with the atmosphere on short timescales, and its circulation also transports heat across the face of the planet.  I am specifically interested in reconstructing changes in deep water mass source and structure and determining how these are linked with changes in deep ocean nutrient contents and overturning rate.  

My research group at Cambridge uses radiogenic isotopes, including those of Nd and Pb, and other geochemical tools, at globally distributed sites to gain a big picture view of past ocean geochemistry.   A number of my studies have used Nd isotopes to examine South Atlantic deep water sourcing changes during glacial–interglacial transitions (Piotrowski et al., 2005, Science), and glacial millennial-scale variability (Piotrowski et al., 2008, EPSL).  My research group is measuring Nd isotopes records at key locations in the deep ocean, including the the Atlantic (Piotrowski et al., EPSL 2012, Roberts et al., EPSL 2010, GCA 2012, Howe et al., Geology 2016) Indian Ocean (Piotrowski et al., EPSL 2009, Wilson et al., EPSL 2012) and Pacific (Noble et al., EPSL 2013, Hu et al., EPSL 2016).  My research group also was the first to relate how past changes in water-mass source to changes in the circulation strength in the North Atlantic using neodymium isotopes and proxies of deep ocean circulation including ²³¹Pa/²³⁰Th (Roberts et al., Science 2010), allowing a better understanding of the dynamics of past ocean circulation changes and its link to palaeoclimate changes. As a result of these studies a coherent picture of global thermohaline circulation changes during the last glacial cycle is emerging from our robust dataset (Howe et al., Nature Communications, 2016, Hu et al., EPSL 2016).  We are also interfacing geochemical measurements of dissolved chemistry with that of detrital sediment to investigate past changes in terrestrial weathering, sediment input to the ocean, and transport within the ocean circulation system.