244 research outputs found
Tropical cyclones within the sedimentary record : analyzing overwash deposition from event to millennial timescales
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 February 2009.Tropical cyclone activity over the last 5000 years is investigated using overwash
sediments from coastal lagoons on the islands of Vieques, Puerto Rico and Koshikijima,
Japan. A simple sediment transport model can reproduce the landward fining deposits
observed at Vieques, and reveals that although the record exhibits centennial-tomillennial
changes in hurricane overwash frequency, the magnitude of these flooding
events has remained relatively constant. Stochastic simulations of hurricane overwash
show that breaks in activity at Vieques are extremely long and unlikely to occur under the
current hurricane climatology and the present barrier morphology. Periods of less
frequent hurricane deposition at Vieques are contemporaneous with intervals of increased
El Niño occurrences and reduced precipitation in West Africa, suggesting a dominant
influence by these two climatic phenomena. Hiatuses in overwash activity between 3600-
to-2500 and 1000-500 years ago are longer than what is generated by overwash
simulations under a constant El Niño-like state, indicating that mechanisms in addition to
variability in the El Niño/Southern Oscillation are required to completely produce the
overwash variability at Vieques. Periods of low overwash activity at Vieques are
concurrent with increased overwash activity at Kamikoshiki and may indicate a
correspondence between tropical cyclone activity in the western Northern Atlantic and
the western North Pacific.Funding for this research was provided by the Earth Systems History Program of
the National Science Foundation, the Risk Prediction Initiative, the National Geographic
Society, the Andrew W. Mellon Foundation Endowed Fund for Innovative Research, and
graduate student fellowships from the Coastal Ocean Institute at Woods Hole
Oceanographic Institution and the United States Geological Survey
Sediment deposition in the lower Hudson River estuary
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1999This study uses geophysical and sedimentological data collected from the
Lower Hudson River estuary to identify the depositional response of the estuary
to high river discharge events. Erosional and depositional environments in the
estuary are identified through the use of side-scan sonar, bottom penetrating
sonar and surficial sediment sampling. Sediment cores are used to document
deposit thicknesses and to obtain the spatial distribution of estuarine deposits.
Results show a high degree of spatial and temporal variability in sedimentation within the estuary. Two primary deposits are identified underneath the
turbidity maximum for the estuary. Approximately 300,000 metric tons of sediment were deposited within these two deposits during May and June of 1998.
This short-term accumulation underneath the turbidity maximum of the estuary can account for 30 to 98 percent of the estimated, river-borne sediment
load supplied to the estuary during the 1997-1998 water year. Both the tidally
produced stratigraphy observed in sediment cores and the spatial distribution
of identified deposits, support the theory that sedimentation underneath the
turbidity maximum of the estuary is primarily the results of a convergence in
bottom water flow, caused by the formation of a salinity front during ebb tide.This research was funded by the Hudson River Foundation and a National Science
Foundation Coastal Trainee Fellowship
MultiLog: a tool for the control and output merging of multiple logging applications
MultiLog is a logging tool that controls, gathers, and combines the output, on-the-fly, from existing research and commercial logging applications or “loggers.” Loggers record a specific set of user actions on a computing device, helping researchers to better understand environments or interactions, guiding the design of new or improved interfaces and applications. MultiLog reduces researchers’ required implementation effort by simplifying the set-up of multiple loggers and seamlessly combining their output. This in turn increases the availability of logging systems to non-technical experimenters for both short-term and longitudinal observation studies. MultiLog supports two operating modes: “researcher mode” where experimenters configure multiple logging systems, and “deployment mode” where the system is deployed to user-study participants’ systems. Researcher mode allows researchers to install, configure log filtering and obfuscation, observe near real-time event streams, and save configuration files ready for deployment. Deployment mode simplifies data collection from multiple loggers by running in the system tray at user log-in, starting loggers, combining their output, and securely uploading the data to a web-server. It also supports real-time browsing of log data, pausing of logging, and removal of log lines. Performance evaluations show that MultiLog does not adversely affect system performance, even when simultaneously running several logging systems. Initial studies show the system runs reliably over a period of 10 weeks
Data transfer: A longitudinal analysis of clipboard and drag-and-drop use in desktop applications
Data transfer within and between desktop applications facilitates efficient data-centric tasks on modern computer operating systems. This data can be transferred via the clipboard (cut, copy, paste) or through more direct drag-and-drop actions. This paper presents results gathered during a 90-day longitudinal log study of 17 participants’ clipboard and drag-and-drop interactions. The paper characterises the frequency, time and type of actions, interaction mechanism, and whether the users’ computer configuration affects these findings. We found clipboard operations are more common than drag-and-drop operations (and drag-and-drop is rarely used by some participants), most data transfer occurs on the same screen for multi-screen users, clipboard and drag-and-drop operations are used for different applications and the applications used for clipboard operations align with previously reported results
Understanding and improving cross-application interaction in desktop computing
Cross-application interaction on modern computer operating systems is becoming more prevalent as users begin to work more dynamically and utilise more applications simultaneously to complete a task. Such tasks could consist of writing a research paper, developing software or preparing a presentation. These tasks all require the use of multiple applications to complete. However, the interaction between these applications is still poorly understood. At present the research community does not have an extensive overview of the ways in which users work with multiple applications to complete tasks. Previous research mainly focusses on interaction within windows which lacks the cross-application element. Data flow between applications is also not fully understood. Research into a more conceptual, higher level approach to working, with a view to understanding how interaction and communication between these applications aids users when completing tasks, is required. This work has two main aims: 1) To understand how users utilise the open application set to complete tasks and 2) To improve cross-application interaction for users. Within (1) MultiLog (an extensive logging framework) is presented. The MultiLog system is used to gather data during a 90 day study logging users’ interactions with their PCs. This data is then analysed and presented. Within (2) this thesis uses these results to inform the design of QuickFileAccess which aids users when locating folders by dynamically managing the Windows Quick Access list. The results of the log study enabled previously published results to be updated. New results in the area of data transfer, covered a deep understanding of not only how users employed the Windows clipboard to transfer data between applications, but also how participants utilised the “drag-and-drop” facility for data transfer. Results informed the design and development of the QuickFileAccess tool
Watershed Suspended Sediment Supply and Potential Impacts of Dam Removals for an Estuary
Observations and modeling are used to assess potential impacts of sediment releases due to dam removals on the Hudson River estuary. Watershed sediment loads are calculated based on sediment-discharge rating curves for gauges covering 80% of the watershed area. The annual average sediment load to the estuary is 1.2 Mt, of which about 0.6 Mt comes from side tributaries. Sediment yield varies inversely with watershed area, with regional trends that are consistent with substrate erodibility. Geophysical and sedimentological surveys in seven subwatersheds of the Lower Hudson were conducted to estimate the mass and composition of sediment trapped behind dams. Impoundments were classified as (1) active sediment traps, (2) run-of-river sites not actively trapping sediment, and (3) dammed natural lakes and spring-fed ponds. Based on this categorization and impoundment attributes from a dam inventory database, the total mass of impounded sediment in the Lower Hudson watershed is estimated as 4.9 ± 1.9 Mt. This represents about 4 years of annual watershed supply, which is small compared with some individual dam removals and is not practically available given current dam removal rates. More than half of dams impound drainage areas less than 1 km2, and play little role in downstream sediment supply. In modeling of a simulated dam removal, suspended sediment in the estuary increases modestly near the source during discharge events, but otherwise effects on suspended sediment are minimal. Fine-grained sediment deposits broadly along the estuary and coarser sediment deposits near the source, with transport distance inversely related to settling velocity
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Indigenous Knowledge and Climate Adaptation Science
Through this seminar we seek to engage and partner with environmental coordinators, scholars and elders from Tribal Nations to explore prominent examples of Indigenous climate adaptation science, models for collaboration on diverse knowledges in scientific research, and the co-creation of best practices for resilience and adaptation to our rapidly changing climate. Format: 3-week rotations of paired Tribal Elders/Knowledge Keepers and Tribal Scholars/Environmental Coordinators. Each module will focus on a particular climate related topic and will be matched to the particular expertise of the module’s pair of invitees
Grain-size analysis of hurricane-induced event beds in a New England salt marsh, Massachusetts, USA
Author Posting. © Coastal Education and Research Foundation, 2021. This article is posted here by permission of Coastal Education and Research Foundation for personal use, not for redistribution. The definitive version was published in Journal of Coastal Research 37(2), (2021): 326-33, https://doi.org/10.2112/JCOASTRES-D-19-00159.1.Tropical cyclones pose a growing threat to coastal infrastructure and livelihood. Because instrumental and historic records are too short to help us understand interactions between tropical cyclones and climate on a longer scale, proxy records are the only means for reconstructing millennia of tropical cyclone impacts. This study determines grain-size trends in storm-induced overwash deposits along a transect of sediment cores from a salt marsh in Mattapoisett, Massachusetts, to characterize sorting trends and compare deposits associated with individual storms. The overwash deposits preserved within the high-marsh peat provide a record spanning the last two millennia. Building on a 2010 study, a different approach was used to accurately determine the grain-size distribution of overwash deposits from cores in a transect running perpendicular to the adjacent sandy/gravely barrier. Although maximum grain-size values are expected to decrease as distance from the barrier increases, not all event deposits that were studied follow this trend within uncertainty. Analysis of the storm event beds reveal a significant difference in settling trends between historic and prehistoric deposits, with historic deposits largely displaying landward-fining trends and prehistoric deposits largely displaying landward-coarsening trends. This suggests changes in the hydrodynamic or that geomorphic regime may have altered the way in which storm beds were deposited at this site. This new in-depth, transect-based approach has utility for improving the accuracy of future storm reconstructions, particularly for events for which no historic record exists
Exploring typhoon variability over the mid-to-late Holocene : evidence of extreme coastal flooding from Kamikoshiki, Japan
Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Quaternary Science Reviews 28 (2009): 1774-1785, doi:10.1016/j.quascirev.2009.02.005.Sediment cores from two coastal lakes located on the island of Kamikoshiki in
southwestern Japan (Lake Namakoike and Lake Kaiike) provide evidence for the
response of a backbarrier beach system to episodic coastal inundation over the last 6400
years. Subbottom seismic surveys exhibit acoustically laminated, parallel to subparallel
seismic reflectors, intermittently truncated by erosional unconformities. Sediment cores
collected from targeted depocenters in both lakes contain finely laminated organic mud
interbedded with coarse grained units, with depths of coarse deposits concurrent with
prominent seismic reflectors. The timing of the youngest deposit at Kamikoshiki
correlates to the most recently documented breach in the barrier during a typhoon in 1951
AD. Assuming this modern deposit provides an analog for identifying past events, paleo
typhoons may be reconstructed from layers exhibiting an increase in grain-size, a break in
fine-scale stratigraphy, and elevated Sr concentrations.
Periods of barrier breaching are concurrent with an increase in El Niño frequency,
indicating that the El Niño/Southern Oscillation has potentially played a key role in
governing typhoon variability during the mid-to-late Holocene. An inverse correlation is
observed between tropical cyclone reconstructions from the western North Atlantic and
the Kamikoshiki site, which may indicate an oscillating pattern in tropical cyclone
activity between the western Northern Atlantic and the western North Pacific, or at least
between the western Northern Atlantic and regions encompassing southern Japan. The
two kamikaze typhoons which contributed to the failed Mongol invasions of Japan in
1274 AD and 1281 AD occur during a period with more frequent marine-sourced
deposition at the site, suggesting the events took place during a period of greater regional
typhoon activity.The study was supported by the Coastal Ocean Institute (COI) and the Ocean and Climate Change
Institute (OCCI) at Woods Hole Oceanographic Institute
Turbidity hysteresis in an estuary and tidal river following an extreme discharge event
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ralston, D. K., Yellen, B., Woodruff, J. D., & Fernald, S. Turbidity hysteresis in an estuary and tidal river following an extreme discharge event. Geophysical Research Letters, 47(15), (2020): e2020GL088005, doi:10.1029/2020GL088005.Nonlinear turbidity‐discharge relationships are explored in the context of sediment sourcing and event‐driven hysteresis using long‐term (≥12‐year) turbidity observations from the tidal freshwater and saline estuary of the Hudson River. At four locations spanning 175 km, turbidity generally increased with discharge but did not follow a constant log‐log dependence, in part due to event‐driven adjustments in sediment availability. Following major sediment inputs from extreme precipitation and discharge events in 2011, turbidity in the tidal river increased by 20–50% for a given discharge. The coherent shifts in the turbidity‐discharge relationship along the tidal river over the subsequent 2 years suggest that the 2011 events increased sediment availability for resuspension. In the saline estuary, changes in the sediment‐discharge relationship were less apparent after the high discharge events, indicating that greater background turbidity due to internal sources make event‐driven inputs less important in the saline estuary at interannual time scales.This work was sponsored by the National Estuarine Research Reserve System Science Collaborative, funded by the National Oceanic and Atmospheric Administration and managed by the University of Michigan Water Center (NAI4NOS4190145), with additional support to Yellen and Woodruff from USGS Cooperative Agreement No. G19AC00091
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