TY - JOUR
T1 - Constraining past seawater δ18O and temperature records developed from foraminiferal geochemistry
AU - Thirumalai, Kaustubh
AU - Quinn, Terrence M.
AU - Marino, Gianluca
N1 - Funding Information:
We thank the International Ocean Discovery Program for helping facilitate this project. K.T. thanks the UTIG Ewing-Worzel fellowship, the JSG Lagoe Micropaleontology Fund, and the National Science Foundation under a cooperative agreement with the Consortium for Ocean Leadership as a U.S. Science Support Program for support. G.M.'s postdoctoral fellowship is supported by the Australian Laureate Fellowship project FL120100050 (to E.J. Rohling). This work was supported by the National Science Foundation grant OCE-0902921 to T.M.Q. K.T. thanks J. N. Richey for test piloting PSU Solver. We are grateful to Deborah Khider and an anonymous reviewer for their comments and suggestions, which significantly (p < 0.01) benefitted this manuscript, and also thank Heiko Pälike and an Associate Editor for their help. A copy of PSU Solver with a detailed set of help files, documentation, and example data sets is publicly available online (Mathworks: https://www.mathworks.com/matlabcentral/fileexchange/59565-paleo-seawater-uncertainty-solver; GitHub: https://github.com/holy-kau/PSUSolver) or requested via email from K.T. (kau@ig.utexas.edu). Workers interested in modifying PSU Solver or incorporating new or updated parameters may freely contact K.T. for assistance (if required).
Publisher Copyright:
©2016. American Geophysical Union. All Rights Reserved.
PY - 2016/10/1
Y1 - 2016/10/1
N2 - Paired measurements of magnesium-to-calcium ratios (Mg/Ca) and the stable oxygen isotopic composition (δ18O) in foraminifera have significantly advanced our knowledge of the climate system by providing information on past temperature and seawater δ18O (δ18Osw, a proxy for salinity and ice volume). However, multiple sources of uncertainty exist in transferring these downcore geochemical data into quantitative paleoclimate reconstructions. Here we develop a computational toolkit entitled Paleo-Seawater Uncertainty Solver (PSU Solver) that performs bootstrap Monte Carlo simulations to constrain these various sources of uncertainty. PSU Solver calculates temperature and δ18Osw, and their respective confidence intervals using an iterative approach with user-defined errors, calibrations, and sea-level curves. Our probabilistic approach yields reduced uncertainty constraints compared to theoretical considerations and commonly used propagation exercises. We demonstrate the applicability of PSU Solver for published records covering three timescales: the late Holocene, the last deglaciation, and the last glacial period. We show that the influence of salinity on Mg/Ca can considerably alter the structure and amplitude of change in the resulting reconstruction and can impact the interpretation of paleoceanographic time series. We also highlight the sensitivity of the records to various inputs of sea-level curves, transfer functions, and uncertainty constraints. PSU Solver offers an expeditious yet rigorous approach to test the robustness of past climate variability inferred from paired Mg/Ca-δ18O measurements.
AB - Paired measurements of magnesium-to-calcium ratios (Mg/Ca) and the stable oxygen isotopic composition (δ18O) in foraminifera have significantly advanced our knowledge of the climate system by providing information on past temperature and seawater δ18O (δ18Osw, a proxy for salinity and ice volume). However, multiple sources of uncertainty exist in transferring these downcore geochemical data into quantitative paleoclimate reconstructions. Here we develop a computational toolkit entitled Paleo-Seawater Uncertainty Solver (PSU Solver) that performs bootstrap Monte Carlo simulations to constrain these various sources of uncertainty. PSU Solver calculates temperature and δ18Osw, and their respective confidence intervals using an iterative approach with user-defined errors, calibrations, and sea-level curves. Our probabilistic approach yields reduced uncertainty constraints compared to theoretical considerations and commonly used propagation exercises. We demonstrate the applicability of PSU Solver for published records covering three timescales: the late Holocene, the last deglaciation, and the last glacial period. We show that the influence of salinity on Mg/Ca can considerably alter the structure and amplitude of change in the resulting reconstruction and can impact the interpretation of paleoceanographic time series. We also highlight the sensitivity of the records to various inputs of sea-level curves, transfer functions, and uncertainty constraints. PSU Solver offers an expeditious yet rigorous approach to test the robustness of past climate variability inferred from paired Mg/Ca-δ18O measurements.
KW - error
KW - foraminifera
KW - paired Mg/Ca-δO analysis
KW - paleosalinity
KW - paleotemperature
KW - uncertainty
UR - http://www.scopus.com/inward/record.url?scp=84992316373&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84992316373&partnerID=8YFLogxK
U2 - 10.1002/2016PA002970
DO - 10.1002/2016PA002970
M3 - Article
AN - SCOPUS:84992316373
SN - 2572-4517
VL - 31
SP - 1409
EP - 1422
JO - Paleoceanography and Paleoclimatology
JF - Paleoceanography and Paleoclimatology
IS - 10
ER -