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  • American Meteorological Society (AMS)  (12)
  • Blackwell Publishing Ltd
  • Paleontological Society
  • American Geophysical Union
  • 2015-2019  (17)
  • 1
    Publication Date: 2019-04-04
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Wave generation, dissipation, and disequilibrium in an embayment with complex bathymetry. Journal of Geophysical Research-Oceans, 123(11), (2018): 7856-7876, doi:10.1029/2018JC014381.
    Description: Heterogeneous, sharply varying bathymetry is common in estuaries and embayments, and complex interactions between the bathymetry and wave processes fundamentally alter the distribution of wave energy. The mechanisms that control the generation and dissipation of wind waves in an embayment with heterogeneous, sharply varying bathymetry are evaluated with an observational and numerical study of the Delaware Estuary. Waves in the lower bay depend on both local wind forcing and remote wave forcing from offshore, but elsewhere in the estuary waves are controlled by the local winds and the response of the wavefield to bathymetric variability. Differences in the wavefield with wind direction highlight the impacts of heterogeneous bathymetry and limited fetch. Under the typical winter northwest wind conditions waves are fetch‐limited in the middle estuary and reach equilibrium with local water depth only in the lower bay. During southerly wind conditions typical of storms, wave energy is near equilibrium in the lower bay, and midestuary waves are attenuated by the combination of whitecapping and bottom friction, particularly over the steep, longitudinal shoals. Although the energy dissipation due to bottom friction is generally small relative to whitecapping, it becomes significant where the waves shoal abruptly due to steep bottom topography. In contrast, directional spreading keeps wave heights in the main channel significantly less than local equilibrium. The wave disequilibrium in the deep navigational channel explains why the marked increase in depth by dredging of the modern channel has had little impact on wave conditions.
    Description: Funding was provided by National Science Foundation Coastal SEES: Toward Sustainable Urban Estuaries in the Anthropocene (OCE 1325136) and Ministry of Science and Technology (MOST 107‐2611‐M‐006‐004). We thank James Kirby, Fengyan Shi, and the two anonymous reviewers for their careful reading of our manuscript and their insightful comments. We thank Tracy Quirk for providing wave measurements in Bombay Hook, DE and Stow Creek, NJ. We thank Katie Pijanowski for compiling historical and modern bathymetric data for the estuary. Data supporting this study are posted to Zenodo (http://doi.org/10.5281/zenodo.1433055).
    Description: 2019-04-04
    Keywords: estuarine hydrodynamics ; wave energy ; equilibrium wave ; anthropogenic impact
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2019-06-11
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124 (2019): 196-211, doi:10.1029/2018JC014313.
    Description: Since the late nineteenth century, channel depths have more than doubled in parts of New York Harbor and the tidal Hudson River, wetlands have been reclaimed and navigational channels widened, and river flow has been regulated. To quantify the effects of these modifications, observations and numerical simulations using historical and modern bathymetry are used to analyze changes in the barotropic dynamics. Model results and water level records for Albany (1868 to present) and New York Harbor (1844 to present) recovered from archives show that the tidal amplitude has more than doubled near the head of tides, whereas increases in the lower estuary have been slight (〈10%). Channel deepening has reduced the effective drag in the upper tidal river, shifting the system from hyposynchronous (tide decaying landward) to hypersynchronous (tide amplifying). Similarly, modeling shows that coastal storm effects propagate farther landward, with a 20% increase in amplitude for a major event. In contrast, the decrease in friction with channel deepening has lowered the tidally averaged water level during discharge events, more than compensating for increased surge amplitude. Combined with river regulation that reduced peak discharges, the overall risk of extreme water levels in the upper tidal river decreased after channel construction, reducing the water level for the 10‐year recurrence interval event by almost 3 m. Mean water level decreased sharply with channel modifications around 1930, and subsequent decadal variability has depended both on river discharge and sea level rise. Channel construction has only slightly altered tidal and storm surge amplitudes in the lower estuary.
    Description: Funding for D. K. R., W. R. G., and C. K. S. was provided by NSF Coastal SEES awards OCE-1325136 and OCE-1325102. Funding for S.T. and H. Z. was provided by the U.S. Army Corps of Engineers (award W1927 N-14-2-0015), and NSF (Career Award 1455350). Data supporting this study are posted to Zenodo (https://doi.org/10.5281/zenodo.1298636).
    Description: 2019-06-11
    Keywords: barotropic tides ; flood frequency ; storm surge ; dredging ; estuary ; tidal river
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2019-12-07
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124(7), (2019): 4784-4802, doi: 10.1029/2019JC015006.
    Description: Modifications for navigation since the late 1800s have increased channel depth (H) in the lower Hudson River estuary by 10–30%, and at the mouth the depth has more than doubled. Observations along the lower estuary show that both salinity and stratification have increased over the past century. Model results comparing predredging bathymetry from the 1860s with modern conditions indicate an increase in the salinity intrusion of about 30%, which is roughly consistent with the H5/3 scaling expected from theory for salt flux dominated by steady exchange. While modifications including a recent deepening project have been concentrated near the mouth, the changes increase salinity and threaten drinking water supplies more than 100 km landward. The deepening has not changed the responses to river discharge (Qr) of the salinity intrusion (~Qr−1/3) or mean stratification (Qr2/3). Surprisingly, the increase in salinity intrusion with channel deepening results in almost no change in the estuarine circulation. This contrasts sharply with local scaling based on local dynamics of an H2 dependence, but it is consistent with a steady state salt balance that allows scaling of the estuarine circulation based on external forcing factors and is independent of depth. In contrast, the observed and modeled increases in stratification are opposite of expectations from the steady state balance, which could be due to reduction in mixing with loss of shallow subtidal regions. Overall, the mean shift in estuarine parameter space due to channel deepening has been modest compared with the monthly‐to‐seasonal variability due to tides and river discharge.
    Description: Funding was provided by NSF Coastal SEES (OCE 1325136). Data supporting this study are posted to Zenodo (https://doi.org/10.5281/zenodo.2551285) or are available by contacting the author.
    Description: 2019-12-07
    Keywords: estuarine circulation ; salinity intrusion ; stratification ; dredging ; Hudson River
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2019
    Description: Journal of Physical Oceanography, Ahead of Print. 〈br/〉
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
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  • 5
    Publication Date: 2017-03-09
    Description: The richly fossiliferous Ekspedition Bræ Formation of North Greenland yields a typical oligospecific fossil assemblage with well-preserved trilobites, helcionelloids, and lingulate brachiopods. The trilobites include Itagnostus subhastatus new species, Itagnostus sp. cf. I . gaspensis (Rasetti, 1948), Elrathina aphrodite new species, Elrathina athena new species, Elrathina hera new species, and Elrathia groenlandica new species—a fossil assemblage typical of the Bathyuriscus - Elrathina Zone as known from the Cordilleran regions of Laurentia. Excellent preservation allows a detailed assessment of the prosopon and elucidates aspects of the ontogenetic development of Elrathina and Elrathia . An evaluation of Elrathina includes a redescription of its type species, E . cordillerae (Rominger, 1887), based on the type material, and indicates that most specimens collected from the Burgess Shale and previously dealt with as E . cordillerae represent a new species.
    Print ISSN: 0022-3360
    Electronic ISSN: 1937-2337
    Topics: Geosciences
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  • 6
    Publication Date: 2016-12-20
    Description: The richly fossiliferous Ekspedition Bræ Formation of North Greenland yields a typical oligospecific fossil assemblage with well-preserved trilobites, helcionelloids, and lingulate brachiopods. The trilobites includeItagnostus subhastatusnew species,Itagnostussp. cf.I.gaspensis(Rasetti, 1948),Elrathina aphroditenew species,Elrathina athenanew species,Elrathina heranew species, andElrathia groenlandicanew species—a fossil assemblage typical of theBathyuriscus-ElrathinaZone as known from the Cordilleran regions of Laurentia. Excellent preservation allows a detailed assessment of the prosopon and elucidates aspects of the ontogenetic development ofElrathinaandElrathia. An evaluation ofElrathinaincludes a redescription of its type species,E.cordillerae(Rominger, 1887), based on the type material, and indicates that most specimens collected from the Burgess Shale and previously dealt with asE.cordilleraerepresent a new species.
    Print ISSN: 0022-3360
    Electronic ISSN: 1937-2337
    Topics: Geosciences
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  • 7
    Publication Date: 2015-11-01
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
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  • 8
    Publication Date: 2019-12-26
    Description: Two questions motivated this study: 1) Will meteorological droughts become more frequent and severe during the 21st century? 2) Given the projected global temperature rise, to what extent does the inclusion of temperature (in addition to precipitation) in drought indicators, play a role in future meteorological droughts? To answer, we analyzed the changes in drought frequency, severity, and historically undocumented extreme droughts over 1981-2100, using Standardized Precipitation Index (SPI, including precipitation only) and Standardized Precipitation-Evapotranspiration Index (SPEI, indirectly including temperature), and under two Representative Concentration Pathways (RCP4.5 and RCP8.5). As input data, we employed 103 high-resolution (0.44°) simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX), based on a combination of sixteen Global Circulation Models (GCMs) and twenty Regional Circulation Models (RCMs). This is the first study on global drought projections including RCMs based on such a large ensemble of RCMs. Based on precipitation only, ∼15% of the global land is likely to experience more frequent and severe droughts during 2071-2100 versus 1981-2010 for both scenarios. This increase is larger (∼47% under RCP4.5, ∼49% under RCP8.5) when precipitation and temperature are used. Both SPI and SPEI project more frequent and severe droughts, especially under RCP8.5, over southern South-America, Mediterranean Region, southern Africa, southeastern China, Japan, and southern Australia. A decrease in drought is projected for high-latitudes in Northern Hemisphere and southeastern Asia. If temperature is included, drought characteristics are projected to increase over North America, Amazonia, central Europe and Asia, Horn of Africa, India, and central Australia; if only precipitation is considered, they are found to decrease over those areas.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
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  • 9
    Publication Date: 2016-10-13
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
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  • 10
    Publication Date: 2016-06-01
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
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