Abstract
Our understanding of oceanic variability on timescales longer than the time span of direct oceanographic measurements (about a century for most common measurements) relies on our capability to interpret the marine sediment record. Sediment observations have reached the point where hypotheses regarding oceanic conditions during specific time intervals of the geological past can be tested. An interval of preeminent interest is the Last Glacial Maximum (LGM, ca. 20 kyr BP), when large ice sheets occupied North America and northern Europe, and global sea level was reduced by more than 100 m. Much effort has been devoted to estimating oceanic conditions during the LGM, in particular in the Atlantic basin. Hypotheses regarding the ocean circulation during the LGM are particularly relevant, given the postulated role of ocean circulation in climate change. Here we report on a test of the null hypothesis that observations from glacial sediments in the Atlantic basin are consistent with the modern circulation.
Highlights
LeGrand and Wunsch (1995) ar- from Atlantic sediments (Marchal and Assuming that (i) the δ13C of dissolved inorganic carbon (δ13CDIC) estimates gued that NADW and/or AABW, which Curry, 2008; Fig. 1) to provide a new test have an uncertainty of 0.1‰ and (ii) deep are “formed” at high latitudes, could have of the null hypothesis that these data are water δ13CDIC is governed primarily by a entered the deep Atlantic with initial δ13C consistent with the modern circulation in balance between the effects of water advalues that are different from today, which the abyssal basin
An inverse method vection and organic matter remineralizawould be recorded in the sediment. was applied to produce an estimate of the tion. They showed that different assumptions abyssal circulation in the modern Atlantic its oxidation tends to depress the δ13C of about these initial values lead to signifi- (Fig. 2). This circulation estimate served as ambient DIC), the number of δ13CDIC values cantly different depictions of these water a reference state for the null hypothesis closest to core locations that are adjusted masses in the glacial Atlantic
Be consistent with recent observations, method was used to combine, with the These numbers correspond, respectively, the effect of varying initial composition on modern flow, estimates of two different to 7% and 21% of the total number of inferences about water mass distribution water properties derived from the sedi- δ13CDIC values at grid points closest to core can be significant
Summary
We report on a test of the null hypothesis that observations from glacial sediments in the Atlantic basin are consistent with the modern circulation.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
