Erroneous Model Field Representations in Multiple Pseudoproxy Studies: Corrections and Implications

Pseudoproxy experiments evaluate statistical methods used to reconstruct climate fields from paleoclimatic proxies during the Common Era. These experiments typically employ output from millennial simulations by general circulation models (GCMs). It is demonstrated that multiple published pseudoproxy studies have used erroneously processed GCM surface temperature fields: the NCAR Community Climate System Model (CCSM), version 1.4, field was incorrectly oriented geographically and the GKSS ECHO-g FOR1 field was corrupted by a hemispheric-scale smoothing in the Western Hemisphere. These problems are not associated with the original model simulations; they instead arose because of incorrect processing of the model data for the pseudoproxy experiments. The consequences of these problems are evaluated for the studies in which the incorrect fields were used. Some quantitative results are invalidated by the findings: these include all experiments that used the corrupted ECHO-g field and those aspects of previous CCSM experiments that focused on Niño-3 reconstructions. Other results derived from the CCSM field can be reinterpreted based on the information provided herein and their qualitative characteristics remain similar

Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2016Since the Last Glacial Maximum (LGM, ~ 20,000 years ago) air temperatures warmed, sea level rose roughly 130 meters, and atmospheric concentrations of carbon dioxide increased. This thesis combines global models and paleoceanographic observations to constrain the ocean’s role in storing and transporting heat, salt, and other tracers during this time, with implications for understanding how the modern ocean works and how it might change in the future. • By combining a kinematic ocean model with “upstream” and “downstream” deglacial oxygen isotope time series from benthic and planktonic foraminifera, I show that the data are in agreement with the modern circulation, quantify their power to infer circulation changes, and propose new data locations. • An ocean general circulation model (the MITgcm) constrained to fit LGM sea surface temperature proxy observations reveals colder ocean temperatures, greater sea ice extent, and changes in ocean mixed layer depth, and suggests that some features in the data are not robust. • A sensitivity analysis in the MITgcm demonstrates that changes in winds or in ocean turbulent transport can explain the hypothesis that the boundary between deep Atlantic waters originating from Northern and Southern Hemispheres was shallower at the LGM than it is today.Support for this work came from an MIT Presidential Fellowship, an NSF Graduate Research Fellowship, and grants NASA NNX12AJ93G – Gravity data for ocean circulation and climate studies, NSF OCE-0961713 – Collaborative Research: The Physics and Statistics of Global Sea Level Change, NSF OCE-1060735 – Collaborative Research: Beyond the Instrumental Record - the Ocean Circulation at the last Glacial maximum and the deglacial sequence, and NASA NNX08AR33G – Application of Satellite Altimetry Gravity Winds and in Situ Data to Problems of the Ocean Circulation

A global glacial ocean state estimate constrained by upper-ocean temperature proxies

Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 31 (2018): 8059-8079, doi:10.1175/JCLI-D-17-0769.1.We use the method of least squares with Lagrange multipliers to fit an ocean general circulation model to the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) estimate of near sea surface temperature (NSST) at the Last Glacial Maximum (LGM; circa 23–19 thousand years ago). Compared to a modern simulation, the resulting global, last-glacial ocean state estimate, which fits the MARGO data within uncertainties in a free-running coupled ocean–sea ice simulation, has global-mean NSSTs that are 2°C lower and greater sea ice extent in all seasons in both the Northern and Southern Hemispheres. Increased brine rejection by sea ice formation in the Southern Ocean contributes to a stronger abyssal stratification set principally by salinity, qualitatively consistent with pore fluid measurements. The upper cell of the glacial Atlantic overturning circulation is deeper and stronger. Dye release experiments show similar distributions of Southern Ocean source waters in the glacial and modern western Atlantic, suggesting that LGM NSST data do not require a major reorganization of abyssal water masses. Outstanding challenges in reconstructing LGM ocean conditions include reducing effects from model biases and finding computationally efficient ways to incorporate abyssal tracers in global circulation inversions. Progress will be aided by the development of coupled ocean–atmosphere–ice inverse models, by improving high-latitude model processes that connect the upper and abyssal oceans, and by the collection of additional paleoclimate observations.DEA was supported by a NSF Graduate Research Fellowship and NSF Grant OCE-1060735. OM acknowledges support from the NSF. GF was supported by NASA Award 1553749 and Simons Foundation Award 549931

Reply to “Comments on ‘Erroneous Model Field Representations in Multiple Pseudoproxy Studies: Corrections and Implications’”

The commenters confirm the errors identified and discussed in Smerdon et al., which either invalidated or required the reinterpretation of quantitative results from pseudoproxy experiments presented or used in several earlier papers. These errors have a strong influence on the spatial skill assessments of climate field reconstructions (CFRs), despite their small impacts on skill statistics averaged over the Northern Hemisphere. On the basis of spatial performance and contrary to the claim by the commenters, the Regularized Expectation Maximization method using truncated total least squares (RegEM-TTLS) cannot be considered a preferred CFR technique. Moreover, distinctions between CFR methods in the context of the discussion in the original paper are immaterial. Continued investigations using accurately described and faithfully executed pseudoproxy experiments are critical for further evaluation and improvement of CFR methods

Atlantic circulation change still uncertain

Deep oceanic overturning circulation in the Atlantic (Atlantic Meridional Overturning Circulation, AMOC) is projected to decrease in the future in response to anthropogenic warming. Caesar et al. 1 argue that an AMOC slowdown started in the 19 th century and intensified during the mid-20th century. Although the argument and selected evidence proposed have some merits, we find that their conclusions might be different if a more complete array of data available in the North Atlantic region had been considered. We argue that the strength of AMOC over recent centuries is still poorly constrained and the expected slowdown may not have started yet.K.H.K. acknowledges funding from NOAA grant NA20OAR4310481. D.E.A. and B.L.O.-B. acknowledge support from the National Center for Atmospheric Research, which is a major facility sponsored by the National Science Foundation under cooperative agreement no. 1852977. N.M.W. acknowledges support from a NOAA Climate and Global Change Postdoctoral Fellowship. M.F.J. acknowledges support from NSF award OCE-1846821 and C.M.L. acknowledges support from NSF award OCE-1805029. This is UMCES contribution 6062.Peer ReviewedArticle signat per 17 autors/es: University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, Solomons, MD, USA: K. Halimeda Kilbourne / Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA, USA: Alan D. Wanamaker / Geography Department, Durham University, Durham, UK: Paola Moffa-Sanchez / Centre for Geography and Environmental Sciences, University of Exeter, Penryn, UK: David J. Reynolds, Paul G. Butler & James Scourse / Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA: Daniel E. Amrhein & Bette L. Otto-Bliesner / Woods Hole Oceanographic Institution, Falmouth, MA, USA: Geoffrey Gebbie & Nina M. Whitney / Cooperative Institute for Marine and Atmospheric Studies, University of Miami, Miami, FL, USA: Marlos Goes / Atlantic Oceanographic and Meteorological Laboratory, National Oceanic and Atmospheric Administration, Miami, FL, USA: Marlos Goes / Department of the Geophysical Sciences, The University of Chicago, Chicago, IL, USA: Malte F. Jansen / Oceanography Department, Atmospheric and Environmental Research, Inc., Texas, TX, USA: Christopher M. Little / US Geological Survey, St Petersburg Coastal and Marine Science Center, St Petersburg, FL, USA: Madelyn Mette / Barcelona Supercomputing Center, Barcelona, Spain: Eduardo Moreno-Chamarro & Pablo Ortega / Graduate School of Oceanography, University of Rhode Island, Kingston, RI, USA: Thomas Rossby / University Corporation of Atmospheric Research, Boulder, CO, USA: Nina M. WhitneyPostprint (author's final draft)Matters Arising published on 17 February 2022. The Original Article was published on 25 February 2021

Memory recall in arousing situations – an emotional von Restorff effect?

BACKGROUND: Previous research has demonstrated a relationship between memory recall and P300 amplitude in list learning tasks, but the variables mediating this P300-recall relationship are not well understood. In the present study, subjects were required to recall items from lists consisting of 12 words, which were presented in front of pictures taken from the IAPS collection. One word per list is made distinct either by font color or by a highly arousing background IAPS picture. This isolation procedure was first used by von Restorff. Brain potentials were recorded during list presentation. RESULTS: Recall performance was enhanced for color but not for emotional isolates. Event-related brain potentials (ERP) showed a more positive P300-component for recalled non-isolated words and color-isolated words, compared to the respective non-remembered words, but not for words isolated by arousing background. CONCLUSION: Our findings indicate that it is crucial to take emotional mediator variables into account, when using the P300 to predict later recall. Highly arousing environments might force the cognitive system to interrupt rehearsal processes in working memory, which might benefit transfer into other, more stable memory systems. The impact of attention-capturing properties of arousing background stimuli is also discussed

Manipulating the alpha level cannot cure significance testing

We argue that making accept/reject decisions on scientific hypotheses, including a recent call for changing the canonical alpha level from p = 0.05 to p = 0.005, is deleterious for the finding of new discoveries and the progress of science. Given that blanket and variable alpha levels both are problematic, it is sensible to dispense with significance testing altogether. There are alternatives that address study design and sample size much more directly than significance testing does; but none of the statistical tools should be taken as the new magic method giving clear-cut mechanical answers. Inference should not be based on single studies at all, but on cumulative evidence from multiple independent studies. When evaluating the strength of the evidence, we should consider, for example, auxiliary assumptions, the strength of the experimental design, and implications for applications. To boil all this down to a binary decision based on a p-value threshold of 0.05, 0.01, 0.005, or anything else, is not acceptable