Reconstructing 7000 years of North Atlantic hurricane variability using deep-sea sediment cores from the western Great Bahama Bank

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 28 (2013): 31–41, doi:10.1002/palo.20012.Available overwash records from coastal barrier systems document significant variability in North Atlantic hurricane activity during the late Holocene. The same climate forcings that may have controlled cyclone activity over this interval (e.g., the West African Monsoon, El Niño–Southern Oscillation (ENSO)) show abrupt changes around 6000 yrs B.P., but most coastal sedimentary records do not span this time period. Establishing longer records is essential for understanding mid-Holocene patterns of storminess and their climatic drivers, which will lead to better forecasting of how climate change over the next century may affect tropical cyclone frequency and intensity. Storms are thought to be an important mechanism for transporting coarse sediment from shallow carbonate platforms to the deep-sea, and bank-edge sediments may offer an unexplored archive of long-term hurricane activity. Here, we develop this new approach, reconstructing more than 7000 years of North Atlantic hurricane variability using coarse-grained deposits in sediment cores from the leeward margin of the Great Bahama Bank. High energy event layers within the resulting archive are (1) broadly correlated throughout an offbank transect of multi-cores, (2) closely matched with historic hurricane events, and (3) synchronous with previous intervals of heightened North Atlantic hurricane activity in overwash reconstructions from Puerto Rico and elsewhere in the Bahamas. Lower storm frequency prior to 4400 yrs B.P. in our records suggests that precession and increased NH summer insolation may have greatly limited hurricane potential intensity, outweighing weakened ENSO and a stronger West African Monsoon—factors thought to be favorable for hurricane development.This research was supported by awards from the Division of Ocean Sciences and the Division of Atmospheric and Geospace Sciences of the National Science Foundation to William B. Curry and an NSERC Post-Doctoral Fellowship to Peter van Hengstum.2013-09-1

Increased hurricane frequency near Florida during Younger Dryas Atlantic Meridional Overturning Circulation slowdown

Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Geology 45 (2017): 1047-1050, doi:10.1130/G39270.1.The risk posed by intensification of North Atlantic hurricane activity remains controversial, in part due to a lack of available storm proxy records that extend beyond the relatively stable climates of the late Holocene. Here we present a record of storm-triggered turbidite deposition offshore the Dry Tortugas, south Florida, USA, that spans abrupt transitions in North Atlantic sea-surface temperature and Atlantic Meridional Overturning Circulation (AMOC) during the Younger Dryas (12.9–11.7 k.y. B.P.). Despite potentially hostile conditions for cyclogenesis in the tropical North Atlantic at this time, our record and numerical experiments suggest that strong hurricanes may have regularly impacted Florida. Less severe surface cooling at mid-latitudes (~20–40°N) than across much of the tropical North Atlantic (~10–20°N) in response to AMOC reduction may best explain strong hurricane activity during the Younger Dryas near the Dry Tortugas and, potentially, along the entire southeastern coast of the United States.This work was supported by the U. S. Geological Survey Climate and Land Use Change Research and Development Program (Toomey), the Woods Hole Oceanographic Institution Ocean and Climate Change Institute (Toomey) and National Science Foundation grants (OCE-1356708 to Donnelly; 1356509 to van Hengstum)

Vortex Lattice Locking in Rotating Two-Component Bose-Einstein Condensates

The vortex density of a rotating superfluid, divided by its particle mass, dictates the superfluid's angular velocity through the Feynman relation. To find how the Feynman relation applies to superfluid mixtures, we investigate a rotating two-component Bose-Einstein condensate, composed of bosons with different masses. We find that in the case of sufficiently strong interspecies attraction, the vortex lattices of the two condensates lock and rotate at the drive frequency, while the superfluids themselves rotate at two different velocities, whose ratio is the ratio between the particle mass of the two species. In this paper, we characterize the vortex-locked state, establish its regime of stability, and find that it surives within a disk smaller than a critical radius, beyond which vortices become unbound, and the two Bose-gas rings rotate together at the frequency of the external drive.Comment: 6 pages, 2 figure

Coupling instrumental and geological records of sea-level change : evidence from southern New England of an increase in the rate of sea-level rise in the late 19th century

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 31 (2004): L05203, doi:10.1029/2003GL018933.We construct a high-resolution relative sea-level record for the past 700 years by dating basal salt-marsh peat samples above a glacial erratic in an eastern Connecticut salt marsh, to test whether or not the apparent recent acceleration in the rate of sea-level rise (SLR) is coeval with climate warming. The data reveal an average SLR rate of 1.0 ± 0.2 mm/year from about 1300 to 1850 A.D. Coupling of the regional tide-gauge data (1856 to present) with this marsh-based record indicates that the nearly three-fold increase in the regional rate of SLR to modern levels likely occurred in the later half of the 19th century. Thus the timing of the observed SLR rate increase is coincident with the onset of climate warming, indicating a possible link between historic SLR increases and recent temperature increases.A Research Initiative Grant from the NOSAMS facility at WHOI funded the C-14 analysis. The Postdoctoral Scholar Program at WHOI (with funding provided by the U.S.G.S.), The John E. and Anne W. Sawyer Endowed Fund, and The J. Lamar Worzel Assistant Scientist Fund provided support to J. Donnelly

Comparison of frequency and time domain methods of assessment of cerebral autoregulation in traumatic brain injury.

The impulse response (IR)-based autoregulation index (ARI) allows for continuous monitoring of cerebral autoregulation using spontaneous fluctuations of arterial blood pressure (ABP) and cerebral flow velocity (FV). We compared three methods of autoregulation assessment in 288 traumatic brain injury (TBI) patients managed in the Neurocritical Care Unit: (1) IR-based ARI; (2) transfer function (TF) phase, gain, and coherence; and (3) mean flow index (Mx). Autoregulation index was calculated using the TF estimation (Welch method) and classified according to the original Tiecks' model. Mx was calculated as a correlation coefficient between 10-second averages of ABP and FV using a moving 300-second data window. Transfer function phase, gain, and coherence were extracted in the very low frequency (VLF, 0 to 0.05 Hz) and low frequency (LF, 0.05 to 0.15 Hz) bandwidths. We studied the relationship between these parameters and also compared them with patients' Glasgow outcome score. The calculations were performed using both cerebral perfusion pressure (CPP; suffix 'c') as input and ABP (suffix 'a'). The result showed a significant relationship between ARI and Mx when using either ABP (r=-0.38, P<0.001) or CPP (r=-0.404, P<0.001) as input. Transfer function phase and coherence_a were significantly correlated with ARI_a and ARI_c (P<0.05). Only ARI_a, ARI_c, Mx_a, Mx_c, and phase_c were significantly correlated with patients' outcome, with Mx_c showing the strongest association.This is the accepted manuscript. The final version's available from Nature Publishing at http://dx.doi/10.1038/jcbfm.2014.192

Human arrival and landscape dynamics in the northern Bahamas

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fall, P. L., van Hengstum, P. J., Lavold-Foote, L., Donnelly, J. P., Albury, N. A., & Tamalavage, A. E. Human arrival and landscape dynamics in the northern Bahamas. Proceedings of the National Academy of Sciences of the United States of America, 118(10), (2021): e2015764118, https://doi.org/10.1073/pnas.2015764118.The first Caribbean settlers were Amerindians from South America. Great Abaco and Grand Bahama, the final islands colonized in the northernmost Bahamas, were inhabited by the Lucayans when Europeans arrived. The timing of Lucayan arrival in the northern Bahamas has been uncertain because direct archaeological evidence is limited. We document Lucayan arrival on Great Abaco Island through a detailed record of vegetation, fire, and landscape dynamics based on proxy data from Blackwood Sinkhole. From about 3,000 to 1,000 y ago, forests dominated by hardwoods and palms were resilient to the effects of hurricanes and cooling sea surface temperatures. The arrival of Lucayans by about 830 CE (2σ range: 720 to 920 CE) is demarcated by increased burning and followed by landscape disturbance and a time-transgressive shift from hardwoods and palms to the modern pine forest. Considering that Lucayan settlements in the southern Bahamian archipelago are dated to about 750 CE (2σ range: 600 to 900 CE), these results demonstrate that Lucayans spread rapidly through the archipelago in less than 100 y. Although precontact landscapes would have been influenced by storms and climatic trends, the most pronounced changes follow more directly from landscape burning and ecosystem shifts after Lucayan arrival. The pine forests of Abaco declined substantially between 1500 and 1670 CE, a period of increased regional hurricane activity, coupled with fires on an already human-impacted landscape. Any future intensification of hurricane activity in the tropical North Atlantic Ocean threatens the sustainability of modern pine forests in the northern Bahamas.This research was supported by NSF Awards GSS-1118340 (P.L.F.), OCE-1356509 (P.J.v.H.), OCE-1703087 (P.J.v.H.), and OCE-1356708 (J.P.D.)

Cerebral vasospasm affects arterial critical closing pressure.

The effect of cerebral vasospasm (CVS) after aneurysmal subarachnoid hemorrhage (SAH) on critical closing pressure (CrCP) has not been fully delineated. Using cerebral impedance methodology, we sought to assess the behavior of CrCP during CVS. As CrCP expresses the sum of intracranial pressure (ICP) and vascular wall tension, we also explored its role in reflecting changes in vascular tone occurring in small vessels distal to spasm. This retrospective analysis was performed using recordings from 52 patients, diagnosed with CVS through transcranial Doppler measurements. Critical closing pressure was calculated noninvasively using arterial blood pressure and blood flow velocity. Outcome was assessed at both discharge and 3 months after ictus with the Glasgow Outcome Scale. The onset of CVS caused significant decreases in CrCP (P=0.025), without any observed significant changes in ICP (P=0.134). Vasospasm induced asymmetry, with CrCP ipsilateral to CVS becoming significantly lower than contralateral (P=0.025). Unfavorable outcomes were associated with a significantly lower CrCP after the onset of CVS (discharge: P=0.014; 3 months after SAH: P=0.020). Critical closing pressure is reduced in the presence of CVS in both temporal and spatial assessments. As ICP remained unchanged during CVS, reduced CrCP most probably reflects a lower wall tension in dilated small vessels distal to spasm.GVV is supported by an A.G. Leventis Foundation Scholarship, and a Charter Studentship from St Edmund’s College, Cambridge. AGK is supported by a Royal College of Surgeons of England Research Fellowship, a National Institute for Health Research (NIHR) Academic Clinical Fellowship, and a Raymond and Beverly Sackler Studentship. JD is supported by a Woolf Fisher Trust scholarship. PJH is supported by an NIHR Research Professorship, the NIHR Cambridge Biomedical Research Centre and has been appointed as the Surgical Specialty Lead for Neurosurgery, Royal College of Surgeons of England Clinical Research Initiative. JDP and MC are supported by the NIHR Cambridge Biomedical Research Centre and JDP by NIHR Senior Investigator Award. The prospective study16 on which this retrospective analysis was based, was supported by the National Institute of Health Research, Biomedical Research Centre (Neuroscience Theme). MC was supported by NIHR Cambridge Biomedical Research Centre.This is the accepted manuscript. The final published version is available from Nature Publishing at http://www.nature.com/jcbfm/journal/vaop/ncurrent/full/jcbfm2014198a.html

Revising evidence of hurricane strikes on Abaco Island (the Bahamas) over the last 700 years

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Winkler, T. S., van Hengstum, P. J., Donnelly, J. P., Wallace, E. J., Sullivan, R. M., MacDonald, D., & Albury, N. A. Revising evidence of hurricane strikes on Abaco Island (the Bahamas) over the last 700 years. Scientific Reports, 10(1), (2020): 16556, doi:10.1038/s41598-020-73132-x.The northern Bahamas have experienced more frequent intense-hurricane impacts than almost anywhere else in the Atlantic since 1850 CE. In 2019, category 5 (Saffir-Simpson scale) Hurricane Dorian demonstrated the destructive potential of these natural hazards. Problematically, determining whether high hurricane activity levels remained constant through time is difficult given the short observational record (< 170 years). We present a 700-year long, near-annually resolved stratigraphic record of hurricane passage near Thatchpoint Blue Hole (TPBH) on Abaco Island, The Bahamas. Using longer sediment cores (888 cm) and more reliable age-control, this study revises and temporally expands a previous study from TPBH that underestimated the sedimentation rate. TPBH records at least 13 ≥ category 2 hurricanes per century between 1500 to 1670 CE, which exceeds the 9 ≥ category 2 hurricanes per century within 50 km of TPBH since 1850 CE. The eastern United States also experienced frequent hurricanes from 1500 to 1670 CE, but frequency was depressed elsewhere in the Atlantic Ocean. This suggests that spatial heterogeneity in Atlantic hurricane activity since 1850 CE could have persisted throughout the last millennium. This heterogeneity is impacted by climatic and stochastic forcing, but additional high-resolution paleo-hurricane reconstructions are required to assess the mechanisms that impact regional variability.Field support was provided by Jody Albury and the staff of Friends of the Environment in Marsh Harbour, The Bahamas, and technical support was provided was provided by M. Horgan and S. Molodtsov. Funding for this project was provided by NSF Awards OCE-1356509, OCE-1356708, OCE-1854917, OCE-1903616, and ICER-1854980. The open access publishing fees for this article have been covered by the Texas A&M University Open Access to Knowledge Fund (OAKFund), supported by the University Libraries

Climate forcing of unprecedented intense-hurricane activity in the last 2000 years

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Earth's Future 3 (2015): 49–65, doi:10.1002/2014EF000274.How climate controls hurricane variability has critical implications for society is not well understood. In part, our understanding is hampered by the short and incomplete observational hurricane record. Here we present a synthesis of intense-hurricane activity from the western North Atlantic over the past two millennia, which is supported by a new, exceptionally well-resolved record from Salt Pond, Massachusetts (USA). At Salt Pond, three coarse grained event beds deposited in the historical interval are consistent with severe hurricanes in 1991 (Bob), 1675, and 1635 C.E., and provide modern analogs for 32 other prehistoric event beds. Two intervals of heightened frequency of event bed deposition between 1400 and 1675 C.E. (10 events) and 150 and 1150 C.E. (23 events), represent the local expression of coherent regional patterns in intense-hurricane–induced event beds. Our synthesis indicates that much of the western North Atlantic appears to have been active between 250 and 1150 C.E., with high levels of activity persisting in the Caribbean and Gulf of Mexico until 1400 C.E. This interval was one with relatively warm sea surface temperatures (SSTs) in the main development region (MDR). A shift in activity to the North American east coast occurred ca. 1400 C.E., with more frequent severe hurricane strikes recorded from The Bahamas to New England between 1400 and 1675 C.E. A warm SST anomaly along the western North Atlantic, rather than within the MDR, likely contributed to the later active interval being restricted to the east coast.Funding was provided by US National Science Foundation (awards 0903020 and 1356708), the Risk Prediction Initiative at the Bermuda Institute for Ocean Sciences (BIOS), US Department of Energy National Institute for Climate Change Research, National Oceanic and Atmospheric Administration (award NA11OAR431010), and the Dalio Explore Fund

Cluster-Randomized Test-Negative Design Trials: A Novel and Efficient Method to Assess the Efficacy of Community-Level Dengue Interventions.

Cluster-randomized controlled trials are the gold standard for assessing efficacy of community-level interventions, such as vector-control strategies against dengue. We describe a novel cluster-randomized trial methodology with a test-negative design (CR-TND), which offers advantages over traditional approaches. This method uses outcome-based sampling of patients presenting with a syndrome consistent with the disease of interest, who are subsequently classified as test-positive cases or test-negative controls on the basis of diagnostic testing. We used simulations of a cluster trial to demonstrate validity of efficacy estimates under the test-negative approach. We demonstrated that, provided study arms are balanced for both test-negative and test-positive illness at baseline and that other test-negative design assumptions are met, the efficacy estimates closely match true efficacy. Analytical considerations for an odds ratio-based effect estimate arising from clustered data and potential approaches to analysis are also discussed briefly. We concluded that application of the test-negative design to certain cluster-randomized trials could increase their efficiency and ease of implementation