On the recent destabilization of the Gulf Stream path downstream of Cape Hatteras

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 Geophysical Research Letters 43 (2016): 9836–9842, doi:10.1002/2016GL069966.Mapped satellite altimetry reveals interannual variability in the position of initiation of Gulf Stream meanders downstream of Cape Hatteras. The longitude where the Gulf Stream begins meandering varies by 1500 km. There has been a general trend for the destabilization point to shift west, and 5 of the last 6 years had a Gulf Stream destabilization point upstream of the New England Seamounts. Independent in situ data suggest that this shift has increased both upper-ocean/deep-ocean interaction events at Line W and open-ocean/shelf interactions across the Middle Atlantic Bight (MAB) shelf break. Mooring data and along-track altimetry indicate a recent increase in the number of deep cyclones that stir Deep Western Boundary Current waters from the MAB slope into the deep interior. Temperature profiles from the Oleander Program suggest that recent enhanced warming of the MAB shelf may be related to shifts in the Gulf Stream's destabilization point.NSF Grant Numbers: OCE-1332834, OCE-15585212017-03-2

Spatial and temporal variability of the Gulf Stream near Cape Hatteras

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Andres, M. Spatil and temporal variability of the Gulf Stream near Cape Hatteras. Journal of Geophysical Research: Oceans, 126(9), (2021): e2021JC017579, https://doi.org/10.1029/2021JC017579.In situ observations from a 19-month deployment of current- and pressure-sensor equipped inverted echo sounders (CPIESs) along and across the Gulf Stream near Cape Hatteras capture spatial and temporal variability where this western boundary current separates from the continental margin. Regional hydrographic casts and two temperature cross-sections spanning the Gulf Stream southeast of Cape Hatteras are used with the CPIESs' records of acoustic travel time to infer changes in thermocline depth DT and Gulf Stream position. Wave-like Gulf Stream meanders are observed where the Stream approaches the separation location with periods less than 15 days, wavelengths less than 500-km, and phase speeds between 40 and 70 km d−1. Though meander amplitudes typically decrease by ∼30% on the final approach to Cape Hatteras, some signals are still coherent across the Gulf Stream separation location. Temporal variability in meander intensity may be related to the Loop Current ∼1,400 km upstream. Mesoscale variability is strongest downstream of the separation location where Gulf Stream position is no longer constrained by the steep continental slope. Low frequency transport changes in the Florida Straits are correlated with sea-surface height gradients along the entire South Atlantic Bight (SAB) and with DT inferred at the CPIES sites. The correlations with DT are likely due to coherent transport anomalies in the Gulf Stream approaching the separation location, which then drive Gulf Stream position changes downstream of the separation location. The patterns of coherent transport anomalies may reflect large-scale atmospheric forcing patterns or rapid equatorward propagation of barotropic signals along the SAB.This research was supported by the National Science Foundation through grant OCE-1558521

Laboratory experiments and observations of cyclonic and anticyclonic eddies impinging on an island

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 Journal of Geophysical Research 118 (2013): 762–773, doi:10.1002/jgrc.20081.Laboratory experiments are conducted to investigate the interactions of self-propagating barotropic cyclones and baroclinic anticyclones with an island. Results are interpreted in the context of observations around Okinawa Island, Japan, where ubiquitous arrivals of cyclones and anticyclones on the southeastern side of the island influence the flow around it, thereby impacting both the Ryukyu Current's and the Kuroshio's transport. In the laboratory, baroclinic anticyclones generate a buoyant current that flows clockwise around an island whereas barotropic cyclones generate a counterclockwise current. In both cases, the interaction is governed by conservation of circulation Γ around the island, which establishes a balance between the dissipation along the island in contact with the eddy and the dissipation along the island in contact with the generated current. Laboratory results and scaling analysis suggest that the interaction between an anticyclone (cyclone) and Okinawa Island should result in an instantaneous increase (decrease) of the Ryukyu Current transport and a delayed increase (decrease) of the Kuroshio transport. The estimated delays are in good agreement with those obtained with field measurements suggesting that the dynamics at play in the laboratory may be relevant for the flow around Okinawa Island.M.A.was supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the Ocean and Climate Change Institute and by the Penzance Endowed Fund in Support of Assistant Scientists.2013-08-1

Using acoustic travel time to monitor the heat variability of glacial Fjords

Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 38(9), (2021): 1535–1550, https://doi.org/10.1175/JTECH-D-20-0176.s1.Monitoring the heat content variability of glacial fjords is crucial to understanding the effects of oceanic forcing on marine-terminating glaciers. A pressure-sensor-equipped inverted echo sounder (PIES) was deployed midfjord in Sermilik Fjord in southeast Greenland from August 2011 to September 2012 alongside a moored array of instruments recording temperature, conductivity, and velocity. Historical hydrography is used to quantify the relationship between acoustic travel time and the vertically averaged heat content, and a new method is developed for filtering acoustic return echoes in an ice-influenced environment. We show that PIES measurements, combined with a knowledge of the fjord’s two-layer density structure, can be used to reconstruct the thickness and temperature of the inflowing water. Additionally, we find that fjord–shelf exchange events are identifiable in the travel time record implying the PIES can be used to monitor fjord circulation. Finally, we show that PIES data can be combined with moored temperature records to derive the heat content of the upper layer of the fjord where moored instruments are at great risk of being damaged by transiting icebergs.FS and MA acknowledge funding from the Kerr Family Foundation and the Grossman Family Foundation through the Woods Hole Oceanographic Institution. MA is supported by a grant from the National Science Foundation Office of Polar Programs (1332911). FS and RS acknowledge support from NSF OCE-1657601 and from the Heising-Simons Foundation

Adjustment of a wind-driven two-layer system with mid-basin topography

A linear primitive equations model is used to simulate spin-up of a two-layer ocean bisected by a meridional ridge. The ocean is forced with steady zonal winds east of the ridge. When wind-driven barotropic planetary Rossby waves propagate across the ridge, barotropic and baroclinic anomalies are generated as the barotropic flow adjusts. These ridge-generated anomalies propagate westward from the ridge as planetary Rossby waves and their arrival along the basin\u27s western boundary modulates the western boundary current (WBC) transport and vertical structure. Model results suggest that at short (\u3c1 year) and long (\u3e10 years) delay relative to a change in wind stress curl, net WBC transport, TWBC, is that predicted by the Sverdrup balance for a flat ocean, TSv, but at intermediate delay this balance is disrupted by arrival of the additional barotropic ridge-generated anomalies. The magnitude of the anomalous transport, TWBC, depends on the meridional deflection of the flow at the ridge relative to the length-scale over which wind stress curl varies. The timescale, tBT, associated with adjustment at the ridge is a function of latitude, density contrast between layers and ridge width

Interannual sea level variability in the western North Atlantic : regional forcing and remote response

© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geophysical Research Letters 40 (2013): 5915–5919, doi:10.1002/2013GL058013.Annually averaged sea level (1970–2012) measured by tide gauges along the North American east coast is remarkably coherent over a 1700 km swath from Nova Scotia to North Carolina. Satellite altimetry (1993–2011) shows that this coherent interannual variability extends over the Middle Atlantic Bight, Gulf of Maine, and Scotian Shelf to the shelf break where there is a local minimum in sea level variance. Comparison with National Center for Environmental Prediction reanalysis winds suggests that a significant fraction of the detrended sea level variance is forced by the region's along-shelf wind stress. While interannual changes in sea level appear to be forced locally, altimetry suggests that the changes observed along the coast and over the shelf may influence the Gulf Stream path downstream of Cape Hatteras.M. Andres gratefully acknowledges support from the Woods Hole Oceanographic Institution’s Coastal Ocean Institute. G. Gawarkiewicz acknowledges the support of NSF grant OCE-1129125

Effect of a sheared flow on iceberg motion and melting

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 Geophysical Research Letters 43 (2016): 12,520–12,527, doi:10.1002/2016GL071602.Icebergs account for approximately half the freshwater flux into the ocean from the Greenland and Antarctic ice sheets and play a major role in the distribution of meltwater into the ocean. Global climate models distribute this freshwater by parameterizing iceberg motion and melt, but these parameterizations are presently informed by limited observations. Here we present a record of speed and draft for 90 icebergs from Sermilik Fjord, southeastern Greenland, collected in conjunction with wind and ocean velocity data over an 8 month period. It is shown that icebergs subject to strongly sheared flows predominantly move with the vertical average of the ocean currents. If, as typical in iceberg parameterizations, only the surface ocean velocity is taken into account, iceberg speed and basal melt may have errors in excess of 60%. These results emphasize the need for parameterizations to consider ocean properties over the entire iceberg draft.National Oceanic and AtmosphericAdministration Grant Number: NA14OAR4320106; National Oceanic and Atmospheric Administration, U.S. Department of Commerce NSF Grant Numbers: PLR-1332911, OCE-1434041, OCE-1434041, PLR-13329112017-06-2

Teaching Tolerance in a Globalized World: An Introduction

The increasing diversity of student populations is a global educational trend. The relatively recent rapid influx of immigrants, refugees and asylum seekers, coupled with issues of increasing intolerance, social exclusion and feelings of alienation, and extremism among young people, are posing complex challenges for educational systems around the world. Education has a key role to play in preparing future generations to address these problems and ensuring that young people acquire the social, civic, and intercultural competences needed for active and successful participation in society. This book presents five empirical studies, designed to examine differing factors and conditions that may help schools and teachers in their endeavors to promote tolerance in a globalized world. The 2009 International Civic and Citizenship Education Study (ICCS) provided the research data. This introductory chapter describes the overall theoretical framework, discusses key constructs, and outlines the aims guiding the five studies, concluding with an overview of all chaptersInternational Civic and Citizenship Education Study (ICCS) provided the researchdata. This introductory chapter describes the overall theoretical framework,discusses key constructs, and outlines the aims guiding the five studies, concluding with an overview of all chapters

Atomically thin mica flakes and their application as ultrathin insulating substrates for graphene

We show that it is possible to deposit, by mechanical exfoliation on SiO2/Si wafers, atomically thin mica flakes down to a single monolayer thickness. The optical contrast of these mica flakes on top of a SiO2/Si substrate, which depends on their thickness, the illumination wavelength and the SiO2 substrate thickness, can be quantitatively accounted for by a Fresnel law based model. The preparation of atomically thin insulating crystalline sheets will enable the fabrication of ultrathin defect-free insulating substrates, dielectric barriers or planar electron tunneling junctions. Additionally, we show that few-layer graphene flakes can be deposited on top of a previously transferred mica flake. Our transfer method relies on viscoelastic stamps, as those used for soft lithography. A Raman spectroscopy study shows that such an all-dry deposition technique yields cleaner and higher quality flakes than conventional wet-transfer procedures based on lithographic resists.Comment: 11 pages, 5 figures, 1 graphical abstrac

Icebergs and sea ice detected with inverted echo sounders

Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 32 (2015): 1042–1057, doi:10.1175/JTECH-D-14-00161.1.A 1-yr experiment using a pressure-sensor-equipped inverted echo sounder (PIES) was conducted in Sermilik Fjord in southeastern Greenland (66°N, 38°E) from August 2011 to September 2012. Based on these high-latitude data, the interpretation of PIESs’ acoustic travel-time records from regions that are periodically ice covered were refined. In addition, new methods using PIESs for detecting icebergs and sea ice and for estimating iceberg drafts and drift speeds were developed and tested. During winter months, the PIES in Sermilik Fjord logged about 300 iceberg detections and recorded a 2-week period in early March of land-fast ice cover over the instrument site, consistent with satellite synthetic aperture radar (SAR) imagery. The deepest icebergs in the fjord were found to have keel depths greater than approximately 350 m. Average and maximum iceberg speeds were approximately 0.2 and 0.5 m s−1, respectively. The maximum tidal range at the site was ±1.8 m and during neap tides the range was ±0.3 m, as shown by the PIES’s pressure record.This work was supported by the National Science Foundation through the Divisions of Ocean Science and Polar Programs under Grant PLR-1332911. A. Silvano was supported as a WHOI guest student through a Gori Fellowship