71 research outputs found
Little Ice Age climate in the Western Tropical Atlantic inferred from coral geochemical proxies
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 2016Paleoclimate archives place the short instrumental record of climate variability in
a longer temporal context and allow better understanding of the
rate,
nature
and
extent
by
which
anthropogenic
warming
will
impact
natural
and
human
systems. The ocean is a
key component of the climate system and records of past ocean variability are thus
essential for characterizing natural variability and quantifying climate sensitivity to
radiative forcing. Coral skeletons are high-resolution archives of tropical sea surface
temperatures (SSTs), but inconsistencies call the accuracy of existing coral proxy records
into question. In this thesis, I first quantify the errors associated with the traditional coral
thermometer, Sr/Ca, by comparing in situ logged SST with Sr/Ca-derived SST in four
corals on the same reef. I show that intercolony disparities in mean Sr/Ca, amplitude of
variability, and trend are not due to differences in water temperature, but rather to
âvital effectsâ that result in a ± 2 ÌC uncertainty on reconstructed SST.
I then expand, refine, and test a new paleothermometer, Sr-U, across multiple coral
species and through time. I show that Sr-U captures spatial SST variability with an
uncertainty of ± 0.6 ÌC. When applied to two corals outside of the calibration, Sr-U
accurately captures the mean SST and the 20th century trend in the Western Tropical
Atlantic.
Finally, I apply Sr-U to a coral from the Little Ice Age (LIA) to address uncertainties in
the magnitude of western tropical Atlantic cooling during a 95-year period spanning
1465-1560. Results suggest the region was 1.1 ÌC±0.6°C cooler than the 1958-1988 mean,
but within error of early 20th century SST at this site. Critically, several periods of
warmth, equivalent to the 1958-1988 mean, occurred during a solar minimum that is
widely believed to have been a cool period of the LIA. My results indicate that Sr/Ca
exaggerates the actual cooling by almost 3 °C. My record demonstrates the value of Sr-U
and highlights the need for continuous accurate SST records to better constrain the
amplitude, drivers, and mechanisms of LIA tropical climate change.would like to acknowledge the National Science Foundationâs Graduate
Research Fellowship Program for funding three years of my education. NSF
grants OCE-0926986 to Anne Cohen and Delia Oppo, OCE-1031971to Anne
Cohen, OCE-1338320 to Glenn Gaetani and Anne Cohen supported portions of
my research, fieldwork, and stipend. WHOIâs Ocean Exploration Institute funded
the last year of my stipend. WHOIâs Access to the Sea Program and the
Bermuda Biological Station for Research Fund funded fieldwork. WHOIâs Ocean
Ventures Fund provided me the experience of writing a scientific proposal and
funds for sample analysis. am grateful to research grants as well as travel grants from WHOIâs Academic
Programs Office and the MIT Graduate Student Council for funding my
conference travel expenses
Comparison of equatorial Pacific sea surface temperature variability and trends with Sr/Ca records from multiple corals
Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 31 (2016): 252â265, doi:10.1002/2015PA002897.Coral Sr/Ca is widely used to reconstruct past ocean temperatures. However, some studies report different Sr/Ca-temperature relationships for conspecifics on the same reef, with profound implications for interpretation of reconstructed temperatures. We assess whether these differences are attributable to small-scale oceanographic variability or âvital effectsâ associated with coral calcification and quantify the effect of intercolony differences on temperature estimates and uncertainties. Sr/Ca records from four massive Porites colonies growing on the east and west sides of Jarvis Island, central equatorial Pacific, were compared with in situ logger temperatures spanning 2002â2012. In general, Sr/Ca captured the occurrence of interannual sea surface temperature events but their amplitude was not consistently recorded by any of the corals. No long-term trend was identified in the instrumental data, yet Sr/Ca of one coral implied a statistically significant cooling trend while that of its neighbor implied a warming trend. Slopes of Sr/Ca-temperature regressions from the four different colonies were within error, but offsets in mean Sr/Ca rendered the regressions statistically distinct. Assuming that these relationships represent the full range of Sr/Ca-temperature calibrations in Jarvis Porites, we assessed how well Sr/Ca of a nonliving coral with an unknown Sr/Ca-temperature relationship can constrain past temperatures. Our results indicate that standard error of prediction methods underestimate the actual error as we could not reliably reconstruct the amplitude or frequency of El NiñoâSouthern Oscillation events as large as ± 2°C. Our results underscore the importance of characterizing the full range of temperature-Sr/Ca relationships at each study site to estimate true error.This study was supported by an NSF Graduate Research Fellowship to A.A. and by NSF-OCE-0926986 and NSF-OCE-1031971.2016-08-0
Twentieth century warming of the tropical Atlantic captured by Sr-U paleothermometry
Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 32 (2017): 146â160, doi:10.1002/2016PA002976.Coral skeletons are valuable archives of past ocean conditions. However, interpretation of coral paleotemperature records is confounded by uncertainties associated with single-element ratio thermometers, including Sr/Ca. A new approach, Sr-U, uses U/Ca to constrain the influence of Rayleigh fractionation on Sr/Ca. Here we build on the initial Pacific Porites Sr-U calibration to include multiple Atlantic and Pacific coral genera from multiple coral reef locations spanning a temperature range of 23.15â30.12°C. Accounting for the wintertime growth cessation of one Bermuda coral, we show that Sr-U is strongly correlated with the average water temperature at each location (r2â=â0.91, Pâ<â0.001, nâ=â19). We applied the multispecies spatial calibration between Sr-U and temperature to reconstruct a 96âyear long temperature record at Mona Island, Puerto Rico, using a coral not included in the calibration. Average Sr-U derived temperature for the period 1900â1996 is within 0.12°C of the average instrumental temperature at this site and captures the twentieth century warming trend of 0.06°C per decade. Sr-U also captures the timing of multiyear variability but with higher amplitude than implied by the instrumental data. Mean Sr-U temperatures and patterns of multiyear variability were replicated in a second coral in the same grid box. Conversely, Sr/Ca records from the same two corals were inconsistent with each other and failed to capture absolute sea temperatures, timing of multiyear variability, or the twentieth century warming trend. Our results suggest that coral Sr-U paleothermometry is a promising new tool for reconstruction of past ocean temperatures.NSF Graduate Research Fellowships Grant Numbers: NSF-OCE-1338320, NSF-OCE-1031971, NSF-OCE-0926986;
WHOI Access to the Sea Grant Numbers: 27500056, 0734826;
NSF HRD;
UPR Central Administration to EAHD through the Center for Applied Tropical Ecology and Conservation of UPR2017-08-1
Repeat bleaching of a central Pacific coral reef over the past six decades (1960â2016)
© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Communications Biology 1 (2018): 177, doi:10.1038/s42003-018-0183-7.The oceans are warming and coral reefs are bleaching with increased frequency and severity, fueling concerns for their survival through this century. Yet in the central equatorial Pacific, some of the worldâs most productive reefs regularly experience extreme heat associated with El Niño. Here we use skeletal signatures preserved in long-lived corals on Jarvis Island to evaluate the coral community response to multiple successive heatwaves since 1960. By tracking skeletal stress band formation through the 2015-16 El Nino, which killed 95% of Jarvis corals, we validate their utility as proxies of bleaching severity and show that 2015-16 was not the first catastrophic bleaching event on Jarvis. Since 1960, eight severe (>30% bleaching) and two moderate (<30% bleaching) events occurred, each coinciding with El Niño. While the frequency and severity of bleaching on Jarvis did not increase over this time period, 2015â16 was unprecedented in magnitude. The trajectory of recovery of this historically resilient ecosystem will provide critical insights into the potential for coral reef resilience in a warming world.Funding for this study was provided by National Science Foundation awards OCE 1537338, OCE 1605365, and OCE 1031971 to A.L.C., and the Robertson Foundation to A.L.C., National Science Foundation Graduate Research Fellowships to T.M.D. and A.E.A., and a National Defense Science and Engineering Graduate Fellowship to H.E.R
Mid-Holocene, coral-based sea surface temperatures in the western tropical Atlantic
© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution-NonCommercialâNoDerivs License. The definitive version was published in Rodriguez, L. G., Cohen, A. L., Ramirez, W., Oppo, D. W., Pourmand, A., Edwards, R. L., Alpert, A. E., & Mollica, N. Mid-Holocene, coral-based sea surface temperatures in the western tropical Atlantic. Paleoceanography and Paleoclimatology, 34(7), (2019): 1234-1245, doi:10.1029/2019PA003571.The Holocene is considered a period of relative climatic stability, but significant proxy dataâmodel discrepancies exist that preclude consensus regarding the postglacial global temperature trajectory. In particular, a midâHolocene Climatic Optimum, ~9,000 to ~5,000 years BP, is evident in Northern Hemisphere marine sediment records, but its absence from model simulations raises key questions about the ability of the models to accurately simulate climate and seasonal biases that may be present in the proxy records. Here we present new midâHolocene sea surface temperature (SST) data from the western tropical Atlantic, where twentiethâcentury temperature variability and amplitude of warming track the twentiethâcentury global ocean. Using a new coral thermometer SrâU, we first developed a temporal SrâU SST calibration from three modern Atlantic corals and validated the calibration against SrâU time series from a fourth modern coral. Two fossil corals from the Enriquillo Valley, Dominican Republic, were screened for diagenesis, Uâseries dated to 5,199 ± 26 and 6,427 ± 81 years BP, respectively, and analyzed for Sr/Ca and U/Ca, generating two annually resolved SrâU SST records, 27 and 17 years long, respectively. Average SSTs from both corals were significantly cooler than in early instrumental (1870â1920) and late instrumental (1965â2016) periods at this site, by ~0.5 and ~0.75 °C, respectively, a result inconsistent with the extended midâHolocene warm period inferred from sediment records. A more complete sampling of Atlantic Holocene corals can resolve this issue with confidence and address questions related to multidecadal and longerâterm variability in Holocene Atlantic climate.This study was supported by NSF OCE 1747746 to Anne Cohen and by NSF OCE 1805618 to Anne Cohen and Delia Oppo. Eric Loss and his crew on Pangaea Exploration's Sea Dragon enabled fieldwork in Martinique, and George P. Lohman, Thomas DeCarlo, and Hanny Rivera assisted with coral coring. Kathryn Pietro and Julia Middleton assisted in the laboratory, and Louis Kerr provided technical support on the SEM at MBL. Gretchen Swarr provided technical support on the Element and iCap ICPMS at WHOI. We also thank Edwin Hernandez, Jose Morales, and Amos Winter for discussion. All data generated in this study will be made publicly available at http://www.ncdc.noaa.gov/dataâ access/paleoclimatologyâdata/dataset
ACC/AHA guidelines for percutaneous coronary intervention (revision of the 1993 PTCA guidelines)âexecutive summary21When citing this document, the American College of Cardiology and the American Heart Association would appreciate the following citation format: Smith SC, Jr, Dove JT, Jacobs AK, Kennedy JW, Kereiakes D, Kern MJ, Kuntz RE, Popma JJ, Schaff HV, Williams DO. ACC/AHA guidelines for percutaneous coronary intervention: executive summary and recommendations: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1993 Guidelines for Percutaneous Transluminal Coronary Angioplasty). J Am Coll Cardiol 2001;37:2215â38.22Address for reprints: a single reprint of this document is available by calling 800-253-4636 (US only) or writing the American College of Cardiology, Educational Services, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. This document (reprint no. 71-0205), as well as the companion full-text guideline (reprint no. 71-0206), are available on the ACC Web site at www.acc.organd the AHA Web site at http://www.americanheart.org. To purchase additional reprints (specify version): up to 999 copies, call 800-611-6083 (US only) or fax 413-665-2671; 1000 or more copies, call 214-706-1466, fax 214-691-6342; or E-mail: [email protected]. A report of the American College of Cardiology/American Heart Association Task Force on practice guidelines (Committee to revise the 1993 guidelines for percutaneous transluminal coronary angioplasty) endorsed by the Society for Cardiac Angiography and Interventions
Patient experience of home and waiting room blood pressure measurement: a qualitative study of patients with recently diagnosed hypertension
Background Out-of-office blood pressure (BP) measurement is advocated to confirm hypertension diagnosis. However, little is known about how primary care patients view and use such measurement.Aim To investigate patient experience of out-of-office BP monitoring, particularly home and practice waiting room BP measurement, before, during, and after diagnosis.Design and setting A cross-sectional, qualitative study with patients from two UK GP surgeries participating in a feasibility study of waiting room BP measurement.Method Interviewees were identified from recent additions to the practice hypertension register. Interviews were recorded, transcribed, and coded thematically.Results Of 29 interviewees, 9 (31%) and 22 (76%) had used the waiting room monitor and/or monitored at home respectively. Out-of-office monitoring was used by patients as evidence of control or the lack of need for medication, with the printed results slips from the waiting room monitor perceived to improve âtrustworthinessâ. The waiting room monitor enabled those experiencing uncertainty about their equipment or technique to double-check readings. Monitoring at home allowed a more intensive and/or flexible schedule to investigate BP fluctuations and the impact of medication and lifestyle changes. A minority used self-monitoring to inform drug holidays. Reduced intensity of monitoring was reported with both modalities following diagnosis as initial anxiety or patient and GP interest decreased.Conclusion Home and practice waiting room measurements have overlapping but differing roles for patients. Waiting room BP monitors may be a useful out-of-office measurement modality for patients unwilling and/or unable to measure and record their BP at home
ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia DevicesâSummary Article A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/NASPE Committee to Update the 1998 Pacemaker Guidelines) 11This document was approved by the American College of Cardiology Foundation Board of Trustees in September 2002, the American Heart Association Science Advisory and Coordinating Committee in August 2002, and the North American Society for Pacing and Electrophysiology in August 2002.22The ACC/AHA Task Force on Practice Guidelines makes every effort to avoid any actual or potential conflicts of interest that might arise as a result of an outside relationship or personal interest of a member of the writing panel. Specifically, all members of the writing panel are asked to provide disclosure statements of all such relationships that might be perceived as real or potential conflicts of interest. These statements are reviewed by the parent task force, reported orally to all members of the writing panel at the first meeting, and updated as changes occur. The conflict of interest information for the writing committee members is posted on the ACC, AHA, and NASPE Web sites with the full-length version of the update.33When citing this document, the ACC, the AHA, and NASPE would appreciate the following citation format: Gregoratos G, Abrams J, Epstein AE, Freedman RA, Hayes DL, Hlatky MA, Kerber RE, Naccarelli GV, Schoenfeld MH, Silka MJ, Winters SL. ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia DevicesâSummary Article: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/NASPE Committee to Update the 1998 Pacemaker Guidelines). J Am Coll Cardiol2002;40:1703â19.44Copies: This document is available on the World Wide Web sites of the ACC (www.acc.org) and the AHA (www.americanheart.org). A single copy of the complete guidelines is available by calling 800-253-4636 (US only) or writing the American College of Cardiology, Resource Center, 9111 Old Georgetown Road, Bethesda, MD 20814-1699 (ask for No. 71-0237). To obtain a copy of the Summary Article, ask for reprint No. 71-0236. To purchase additional reprints (specify version and reprint number): up to 999 copies, call 800-611-6083 (US only) or fax 413-665-2671; 1000 or more copies, call 410-528-4426, fax 410-528-4264, or e-mail [email protected](J Am Coll Cardiol 2002;40:1703â19.)66©2002 by the American College of Cardiology Foundation and the American Heart Association, Inc.
ACC/AHA Guidelines for the Management of Patients With ST-Elevation Myocardial InfarctionâExecutive Summary A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1999 Guidelines for the Management of Patients With Acute Myocardial Infarction)
Although considerable improvement has occurred in the process of care for patients with ST-elevation myocardial infarction (STEMI), room for improvement exists (1â3). The purpose of the present guideline is to focus on the numerous advances in the diagnosis and management of patients with STEMI since 1999. This is reflected in the changed name of the guideline: âACC/AHA Guidelines for the Management of Patients With ST-Elevation Myocardial Infarction.â The final recommendations for indications for a diagnostic procedure, a particular therapy, or an intervention in patients with STEMI summarize both clinical evidence and expert opinion (Table 1).To provide clinicians with a set of recommendations that can easily be translated into the practice of caring for patients with STEMI, this guideline is organized around the chronology of the interface between the patient and the clinician. The full guideline is available at http://www.acc.org/clinical/guidelines/stemi/index.htm
ACC/AHA/ASNC Guidelines for the Clinical Use of Cardiac Radionuclide ImagingâExecutive Summary A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASNC Committee to Revise the 1995 Guidelines for the Clinical Use of Cardiac Radionuclide Imaging)44The ACC/AHA Task Force on Practice Guidelines makes every effort to avoid any actual or potential conflicts of interest that might arise as a result of an outside relationship or personal interest of a member of the writing panel. Specifically, all members of the writing panel are asked to provide disclosure statements of all such relationships that might be perceived as real or potential conflicts of interest. These statements are reviewed by the parent task force, reported orally to all members of the writing panel at the first meeting, and updated as changes occur.55This document was approved by the American College of Cardiology Foundation Board of Trustees in July, 2003, the American Heart Association Science Advisory and Coordinating Committee in July, 2003, and the American Society of Nuclear Cardiology Board of Directors in July, 2003.66When citing this document, the American College of Cardiology Foundation, the American Heart Association, and the American Society of Nuclear Cardiology request that the following citation format be used: Klocke FJ, Baird MG, Bateman TM, Berman DS, Carabello BA, Cerqueira MD, DeMaria AN, Kennedy JW, Lorell BH, Messer JV, OâGara PT, Russell RO Jr, St. John Sutton MG, Udelson JE, Verani MS, Williams KA. ACC/AHA/ASNC guidelines for the clinical use of cardiac radionuclide imagingâexecutive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASNC Committee to Revise the 1995 Guidelines for the Clinical Use of Radionuclide Imaging). J Am Coll Cardiol 2003;42:1318â33.77(J Am Coll Cardiol 2003;42:1318â33)88©2003 by the American College of Cardiology Foundation and the American Heart Association, Inc.
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