Tracer transport timescales and the observed Atlantic-Pacific lag in the timing of the Last Termination
Gebbie, Geoffrey A.
MetadataShow full item record
The midpoint of the Last Termination occurred 4,000 years earlier in the deep Atlantic than the deep Pacific according to a pair of benthic foraminiferal δ18O records, seemingly implying an internal circulation shift because the lag is much longer than the deep radiocarbon age. Here a scenario where the lag is instead caused by regional surface boundary condition changes, delays due to oceanic transit timescales, and the interplay between temperature and seawater δ18O (δ18Ow) is quantified with a tracer transport model of the modern-day ocean circulation. Using an inverse method with individual Green functions for 2,806 surface sources, a time history of surface temperature and δ18Ow is reconstructed for the last 30,000 years that is consistent with the foraminiferal oxygen-isotope data, Mg/Ca-derived deep temperature, and glacial pore water records. Thus, in the case that the ocean circulation was relatively unchanged between glacial and modern times, the interbasin lag could be explained by the relatively late local glacial maximum around Antarctica where surface δ18Ow continues to rise even after the North Atlantic δ18Ow falls. The arrival of the signal of the Termination is delayed at the Pacific core site due to the destructive interference of the still-rising Antarctic signal and the falling North Atlantic signal. This scenario is only possible because the ocean is not a single conveyor belt where all waters at the Pacific core site previously passed the Atlantic core site, but instead the Pacific core site is bathed more prominently by waters with a direct Antarctic source.
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 27 (2012): PA3225, doi:10.1029/2011PA002273.
Showing items related by title, author, creator and subject.
Mixing in the North Atlantic Tracer Release Experiment : observations and numerical simulations of Lagrangian particles and passive tracer Sundermeyer, Miles A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1995-09)Mixing and stirring of passive tracer and Lagrangian particles in the open ocean was studied through comparison of observations from the North Atlantic Tracer Release Experiment, a numerical model, and existing theory. ...
Huybers, Peter; Gebbie, Geoffrey A.; Marchal, Olivier (American Meteorological Society, 2007-02)The ability of paleoceanographic tracers to constrain rates of transport is examined using an inverse method to combine idealized observations with a geostrophic model. Considered are the spatial distribution, accuracy, ...
Fate of nitrogen in riparian forest soils and trees : an N-15 tracer study simulating salmon decay Drake, Deanne C.; Naiman, Robert J.; Bechtold, J. Scott (2005-05-23)We introduced a 15N-NH4+ tracer to the riparian forest of a salmon-bearing stream (Kennedy Creek, Washington, USA) to quantify the cycling and fate of a late-season pulse of salmon-N, and, ultimately, mechanisms regulating ...