Compounding impact of severe weather events fuels marine heatwave in the coastal ocean

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Dzwonkowski, B., Coogan, J., Fournier, S., Lockridge, G., Park, K., & Lee, T. Compounding impact of severe weather events fuels marine heatwave in the coastal ocean. Nature Communications, 11(1), (2020): 4623, doi:10.1038/s41467-020-18339-2.Exposure to extreme events is a major concern in coastal regions where growing human populations and stressed natural ecosystems are at significant risk to such phenomena. However, the complex sequence of processes that transform an event from notable to extreme can be challenging to identify and hence, limit forecast abilities. Here, we show an extreme heat content event (i.e., a marine heatwave) in coastal waters of the northern Gulf of Mexico resulted from compounding effects of a tropical storm followed by an atmospheric heatwave. This newly identified process of generating extreme ocean temperatures occurred prior to landfall of Hurricane Michael during October of 2018 and, as critical contributor to storm intensity, likely contributed to the subsequent extreme hurricane. This pattern of compounding processes will also exacerbate other environmental problems in temperature-sensitive ecosystems (e.g., coral bleaching, hypoxia) and is expected to have expanding impacts under global warming predictions.This work would not have been possible without the help of the Tech Support Group at the Dauphin Island Sea Lab. A portion of this work was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. This research was made possible by the NOAA RESTORE Science Program (NA17NOS4510101 and NA19NOS4510194) and NOAA NGI NMFS Regional Collaboration Network (18-NGI3-61)

Crustal structure of the Trans-Atlantic Geotraverse (TAG) segment (Mid-Atlantic Ridge, 26°10′N) : implications for the nature of hydrothermal circulation and detachment faulting at slow spreading ridges

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 8 (2007): Q08004, doi:10.1029/2007GC001629.New seismic refraction data reveal that hydrothermal circulation at the Trans-Atlantic Geotraverse (TAG) hydrothermal field on the Mid-Atlantic Ridge at 26°10′N is not driven by energy extracted from shallow or mid-crustal magmatic intrusions. Our results show that the TAG hydrothermal field is underlain by rocks with high seismic velocities typical of lower crustal gabbros and partially serpentinized peridotites at depth as shallow as 1 km, and we find no evidence for low seismic velocities associated with mid-crustal magma chambers. Our tomographic images support the hypothesis of Tivey et al. (2003) that the TAG field is located on the hanging wall of a detachment fault, and constrain the complex, dome-shaped subsurface geometry of the fault system. Modeling of our seismic velocity profiles indicates that the porosity of the detachment footwall increases after rotation during exhumation, which may enhance footwall cooling. However, heat extracted from the footwall is insufficient for sustaining long-term, high-temperature, hydrothermal circulation at TAG. These constraints indicate that the primary heat source for the TAG hydrothermal system must be a deep magma reservoir at or below the base of the crust.This research was supported by NSF grant OCE-0137329

Plutonic foundation of a slow-spreading ridge segment : oceanic core complex at Kane Megamullion, 23°30′N, 45°20′W

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 9 (2008): Q05014, doi:10.1029/2007GC001645.We mapped the Kane megamullion, an oceanic core complex on the west flank of the Mid-Atlantic Ridge exposing the plutonic foundation of a ∼50 km long, second-order ridge segment. The complex was exhumed by long-lived slip on a normal-sense detachment fault at the base of the rift valley wall from ∼3.3 to 2.1 Ma (Williams, 2007). Mantle peridotites, gabbros, and diabase dikes are exposed in the detachment footwall and in outward facing high-angle normal fault scarps and slide-scar headwalls that cut through the detachment. These rocks directly constrain crustal architecture and the pattern of melt flow from the mantle to and within the lower crust. In addition, the volcanic carapace that originally overlay the complex is preserved intact on the conjugate African plate, so the complete internal and external architecture of the paleoridge segment can be studied. Seafloor spreading during formation of the core complex was highly asymmetric, and crustal accretion occurred largely in the footwall of the detachment fault exposing the core complex. Because additions to the footwall, both magmatic and amagmatic, are nonconservative, oceanic detachment faults are plutonic growth faults. A local volcano and fissure eruptions partially cover the northwestern quarter of the complex. This volcanism is associated with outward facing normal faults and possible, intersecting transform-parallel faults that formed during exhumation of the megamullion, suggesting the volcanics erupted off-axis. We find a zone of late-stage vertical melt transport through the mantle to the crust in the southern part of the segment marked by a ∼10 km wide zone of dunites that likely fed a large gabbro and troctolite intrusion intercalated with dikes. This zone correlates with the midpoint of a lineated axial volcanic high of the same age on the conjugate African plate. In the central region of the segment, however, primitive gabbro is rare, massive depleted peridotite tectonites abundant, and dunites nearly absent, which indicate that little melt crossed the crust-mantle boundary there. Greenschist facies diabase and pillow basalt hanging wall debris are scattered over the detachment surface. The diabase indicates lateral melt transport in dikes that fed the volcanic carapace away from the magmatic centers. At the northern edge of the complex (southern wall of the Kane transform) is a second magmatic center marked by olivine gabbro and minor troctolite intruded into mantle peridotite tectonite. This center varied substantially in size with time, consistent with waxing and waning volcanism near the transform as is also inferred from volcanic abyssal-hill relief on the conjugate African plate. Our results indicate that melt flow from the mantle focuses to local magmatic centers and creates plutonic complexes within the ridge segment whose position varies in space and time rather than fixed at a single central point. Distal to and between these complexes there may not be continuous gabbroic crust, but only a thin carapace of pillow lavas overlying dike complexes laterally fed from the magmatic centers. This is consistent with plate-driven flow that engenders local, stochastically distributed transient instabilities at depth in the partially molten mantle that fed the magmatic centers. Fixed boundaries, such as large-offset fracture zones, or relatively short segment lengths, however, may help to focus episodes of repeated melt extraction in the same location. While no previous model for ocean crust is like that inferred here, our observations do not invalidate them but rather extend the known diversity of ridge architecture.NSF Grants OCE-0118445, OCE-0624408 and OCE-0621660 supported this research. B. Tucholke was also supported by the Henry Bryant Bigelow Chair in Oceanography at Woods Hole Oceanographic Institution

Cascading weather events amplify the coastal thermal conditions prior to the shelf transit of Hurricane Sally (2020)

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Dzwonkowski, B., Fournier, S., Lockridge, G., Coogan, J., Liu, Z., & Park, K. Cascading weather events amplify the coastal thermal conditions prior to the shelf transit of Hurricane Sally (2020). Journal of Geophysical Research: Oceans, 126(12), (2021): e2021JC017957, https://doi.org/10.1029/2021JC017957.Changes in tropical cyclone intensity prior to landfall represent a significant risk to human life and coastal infrastructure. Such changes can be influenced by shelf water temperatures through their role in mediating heat exchange between the ocean and atmosphere. However, the evolution of shelf sea surface temperature during a storm is dependent on the initial thermal conditions of the water column, information that is often unavailable. Here, observational data from multiple monitoring stations and satellite sensors were used to identify the sequence of events that led to the development of storm-favorable thermal conditions in the Mississippi Bight prior to the transit of Hurricane Sally (2020), a storm that rapidly intensified over the shelf. The annual peak in depth-average temperature of >29°C that occurred prior to the arrival of Hurricane Sally was the result of two distinct warming periods caused by a cascade of weather events. The event sequence transitioned the system from below average to above average thermal conditions over a 25-day period. The transition was initiated with the passage of Hurricane Marco (2020), which mixed the upper water column, transferring heat downward and minimizing the cold bottom water reserved over the shelf. The subsequent reheating of the upper ocean by surface heat flux from the atmosphere, followed by downwelling winds, effectively elevated shelf-wide thermal conditions for the subsequent storm, Hurricane Sally. The coupling of climatological downwelling winds and warm sea surface temperature suggest regions with such characteristics are at an elevated risk for storm intensification over the shelf.his paper is a result of research funded by the National Oceanic and Atmospheric Administration's RESTORE Science Program under awards NA17NOS4510101 and NA19NOS4510194 to the University of South Alabama and Dauphin Island Sea Lab and by the NASA Physical Oceanography program under award 80NSSC21K0553 and WBS 281945.02.25.04.67 to the University of South Alabama and the Jet Propulsion Laboratory. A portion of this work was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. We thank the NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Ocean Biology Processing Group for the Moderate-resolution Imaging Spectroradiometer (MODIS) Terra ocean color data; 2014 Reprocessing. NASA OB.DAAC, Greenbelt, MD, USA. 10.5067/AQUA/MODIS/MODIS_OC.2014.0

Perceptions of Light Pollution and its Impacts: Results of an Irish Citizen Science Survey

Background: Light pollution is increasingly an area of concern for health and quality of life research. Somewhat surprisingly, there are relatively few descriptions of perceptions of light pollution in the literature. The current study examined such perceptions in a Irish sample. Methods: A survey was circulated as part of a citizen science initiative of a national newspaper; the survey included questions regarding night sky brightness and the impact of light at night on sleep and animal behaviour. Complete responses from 462 respondents were analysed. Results: Urban location was, as anticipated, associated with reported brighter night skies, and public lighting was reported as the main source of light at night for urban settings, whilst neighbours’ domestic lighting was the most commonly reported source for rural settings. Respondents from rural settings were more likely to report that light at night impinged on sleep, whilst city dwellers were more likely to report recent changes in wildlife behaviour. Conclusions: Citizen science approaches may be useful in gathering data on public perceptions of light pollution and its impacts. In the current study, this perception was strongly influenced by location, highlighting the importance of assessing experiences and attitudes across a number of geographical settings

Perceptions of Light Pollution and its Impacts: Results of an Irish Citizen Science Survey

Background: Light pollution is increasingly an area of concern for health and quality of life research. Somewhat surprisingly, there are relatively few descriptions of perceptions of light pollution in the literature. The current study examined such perceptions in a Irish sample. Methods: A survey was circulated as part of a citizen science initiative of a national newspaper; the survey included questions regarding night sky brightness and the impact of light at night on sleep and animal behaviour. Complete responses from 462 respondents were analysed. Results: Urban location was, as anticipated, associated with reported brighter night skies, and public lighting was reported as the main source of light at night for urban settings, whilst neighbours? domestic lighting was the most commonly reported source for rural settings. Respondents from rural settings were more likely to report that light at night impinged on sleep, whilst city dwellers were more likely to report recent changes in wildlife behaviour. Conclusions: Citizen science approaches may be useful in gathering data on public perceptions of light pollution and its impacts. In the current study, this perception was strongly influenced by location, highlighting the importance of assessing experiences and attitudes across a number of geographical settings

Data supplementing article "Estuarine circulation in a shallow but stratified estuary: Different responses to river discharge between deep ship channel and shoals"

The dataset uploaded includes the measured salinity and velocity at two monitoring stations (one at the lower Mobile Bay and the other at the eastern edge of ship channel in middle Mobile Bay) and from multiple ship cruises crossing the lower, middle, and upper Mobile Bay. Detail information on the measurement frequency, date, and location can be found in the mat files. Records with bad quality are filled with NaN values