James Girton

Physical Oceanography Lunchtime Seminar, Spring 2013

Tuesday, March 26, 2013

12:30 Wednesdays, OSB 425, unless otherwise noted.

Seminar organizer: James Girton, girton (at) apl.washington.edu, 543-8467.

(The schedule of future seminar organizers can be found here.)

To add your name to the announcement e-mail list, please visit https://mailman1.u.washington.edu/mailman/listinfo/phys_ocean_seminars

Date Speaker Institution Title Abstract
Apr 3

Luc Rainville

APL-UW The Tortoise and the Hare: Observations of Internal Waves and Turbulence from Seagliders      

Apr 10

Eric Steig UW Earth and Space Sciences Antarctic surface melt, sub-ice-shelf-melt and the role of the atmosphere and the ocean. An update from the very latest research.  
Apr 17 Zhongxiang Zhao APL-UW

Internal tides from satellite altimetry

Apr 24 Tom Rossby Univ. Rhode Island OceanScope, a new approach to monitoring the oceans – with examples drawn from the recently reprocessed Nuka Arctica ADCP data.                        This talk will focus on the SCOR/IAPSO working group report ‘OceanScope’, which outlines in some detail a proposed partnership with the global shipping industry, and the opportunities it opens up in terms of observation, innovation, and scalability. The initial phase of OceanScope would focus on the North Atlantic for several reasons including already established activities, the strong call for improved observation, and the willingness of industry to assist in developing this capability. By way of example, we will discuss the recently reprocessed Nuka Arctica ADCP data (between Cape Farewell and Scotland), which reveal the striking constraint imposed by bathymetry on both the mean velocity field and the distribution of eddy kinetic energy. The results point to the some tantalizing possibilities for improved observation of the ocean as a dynamic system.
May 1 Ramsey Harcourt APL-UW Modeling Langmuir Turbulence  
May 8 (10 am) Melinda Webster UW Oceanography Spring snow depth on Arctic sea ice using iceBridge Masters Presentation; Advisor: Ignatius Rigor. Note special time: 10am, OSB 425.
May 8 (12:30 pm) Jennifer MacKinnon Scripps/UCSD Diapycnal mixing in the ocean: processes, patterns, and parameterizations  
May 15 Meghan Cronin  NOAA PMEL  Benthic Storms, Dust Storms, and Monitoring Ocean Storms in the Greater Agulhas System                                    Deep current meter data and output from two high-resolution global ocean circulation models are used to determine the prevalence and location of strong bottom currents in the greater Agulhas Current system. The two models and current meter data are remarkably consistent, showing that benthic storms, with bottom currents greater than 0.2 m s-1, occur throughout the Agulhas retroflection region south of Africa more than 20% of the time. Furthermore, beneath the mean Agulhas Current core and the retroflection front, bottom currents exceed 0.2 m s-1 more than 50% of the time, while away from strong surface currents, bottom currents rarely exceed 0.2 m s-1. The study was motivated by the lead author's efforts to deploy a NOAA surface mooring near the Agulhas Return Current. Implications for sediment transport are also discussed and the results are compared to atmospheric storms. Benthic storms of this strength (0.2 m s-1) are comparable to a 9 m s-1 (Beaufort 5) windstorm, but scaling shows that benthic storms may be less effective at lifting and transporting sediment than dust storms. A manuscript describing this study has been accepted for publication in GRL: Cronin, M. F., T. Tozuka, A. Biastoch, J. V. Durgadoo, L. M. Beal. Prevalence of strong bottom currents in the Greater Agulhas System. Geophys. Res. Let., Accepted, 2013.
May 22 Gary Lagerloef Earth and Space Research Latest Results from the Aquarius Salinity Satellite Mission  
May 29 Stephanie Waterman Univ. New South Wales Eddy-mean flow interactions in an idealised western boundary current jet: New insights from the consideration of eddy shape, orientation and propagation


June 5 Noel Pelland UW Oceanography (More) Dispatches from the Washington Coast: Seaglider Surveys Reveal Seasonal Cycles, Mesoscale Variability, and Links to Biology at Multiple Trophic Levels  
June 12 (10:30 am, APL HCC) Beth Curry UW Oceanography An observational study of Davis Strait transports

Davis Strait is one of two main gateways where freshwater from the Arctic enters the North Atlantic. An observing system began operating in Davis Strait in September 2004 with the goal of providing sustained, long-term quantification of Arctic-subarctic exchange west of Greenland. The system, including moorings, Seaglider surveys and autumn hydrographic sections, was designed to quantify volume, freshwater and heat transports and associated uncertainties. The goal of this analysis is to quantify Davis Strait transport variability and identify atmospheric forcing mechanisms driving the variability to help aid in understanding how exchanges between the Arctic and North Atlantic are being modified due to recent changes observed in the Arctic.

Data from six years (2004-10) of continuous measurements give annual volume,
liquid freshwater and temperature transports through Davis Strait of -1.6 ± 0.5
Sv, -93 ± 6 mSv and 23 ± 2 TW, respectively (negative sign indicates southward
transport). Sea ice export contributes additional 11 mSv of freshwater
transport. The array provides the first year-round measurements in the upper
100m and over the shelves, accounting for 38% (-0.6 Sv) of the net volume and 55%
(-51 mSv) of the net freshwater transports. Davis Strait volume and freshwater
fluxes are the same order of magnitude as those from Fram Strait, the other
Arctic outflow gateway.

Although there are no clear trends in the 2004-10 transports, reanalysis of
Davis Strait mooring data from 1987-90 reveals that less Arctic outflow and more
warm, salty North Atlantic inflow occurred in 2004-10 as compared to the
earlier period. A change in Arctic freshwater storage may have also caused a
freshening event observed between September 2009 to August 2010.

Lagged correlation analysis between Davis Strait transport and regional sea
level pressure (SLP) and winds reveals that atmospheric variability within
Baffin Bay significantly influences circulation and transport through Davis
Strait. A seasonal SLP trough, related to high SLP over the Arctic and low SLP
over the subpolar North Atlantic around Greenland and Iceland, establishes in
Baffin Bay beginning around October and weakens rapidly around March and April.
The SLP trough is an important mechanism driving Davis Strait transport.
Transport both northward and southward through Davis Strait is enhanced when the
SLP trough is present and transport is reduced when SLP variability throughout
Baffin Bay and Davis Strait is weak. Variations in winds and SLP in Baffin Bay
are associated with variations observed in the Arctic and North Atlantic but
they are modified and altered due to the inflows and adjustment caused by the
presence of Greenland.

Ph.D. Defense; Advisor: Craig M. Lee. Note special time and location: APL 6th floor Hardisty Conference Center (Henderson Hall Room 602).

June 13 (Thurs) Caroline Harbitz UW Oceanography Upper ocean temperature and salinity response to global tropical cyclones M.S. Exam; Advisors: Riser and Rhines. 12:30 P.M., 425 Ocean Sciences Building. Note special date.
June 18 (Tues, 123 MSB) Nan-Hsun Chi UW Oceanography Variations of Surface Mixed Layer Heat Budget During MJO Events in Central Indian Ocean M.S. Defense; Advisor: Lien. 12:30 pm, 123 Marine Sciences Building. Note special date and location.
June 21 (Fri) Randy Watts Univ. Rhode Island Divergent Eddy Heat Fluxes in Northern Drake Passage 12:30pm; OSB 425; Note special date.
July 10 Dr. Yusuke Kawaguchi JAMSTEC, Yokosuka, Japan A study of a warm baroclinic eddy in the Canda Basin of the Arctic Ocean: Its generation and estimation of heat impact onto environmental waters 12:30pm; OSB 425; Wednesday (i.e., off-season but regular day, time, and place.)


Physical Oceanography Lunchtime Seminar, Winter 2013

Wednesday, October 17, 2012

12:30 Wednesdays, OSB 425. 

Seminar organizer: Matthew Alford, malford (at) uw.edu, 221-3257.

To add your name to the announcement list, please visit https://mailman1.u.washington.edu/mailman/listinfo/phys_ocean_seminars.

Date Speaker Institution Title Abstract
Jan 9 Gunnar Voet APL/UW Flow, mixing and hydraulics in the Samoan Passage  
Jan 16 Cimarron Wortham MIT Space-time scales of low-frequency ocean variability  
Jan 23 NO SEMINAR      
Jan 30 Jacob Wenegrat UW Masters defense: Near-surface Shear Flow on the Equator  
Feb 6 Hayler Dosser UW Properties of Near-Inertial Waves in the Arctic Ocean from Year-Round Observations  
Feb 13 Torge Martin APL/UW Southern Ocean forced multi-centennial climate variability and global impacts Self-sustained oscillations of open ocean deep convection in the Southern Ocean drive a multi–centennial mode of climate variability in the Kiel Climate Model (KCM). The simulated deep convection in the Atlantic Sector of the Southern Ocean has intriguing similarities with the Weddell Polynya observed in the 1970s. The model shows how the competing roles of mid to deep ocean warming and surface freshening in forcing local buoyancy changes can cause global climate variations on a centennial timescale. These can be seen in global surface air temperature, Southern Hemisphere sea ice coverage, Southern Ocean and North Atlantic sea surface height, the Antarctic Circumpolar Current and the Atlantic Meridional Overturning Circulation (AMOC). Because of their magnitude the associated climate variations have the potential to locally mask global warming signals. In this presentation I will explain the mechanism behind the convection flip-flop and how it impacts the AMOC.
Feb 20 Jonathan Nash OSU The Unpredictable Nature of Internal Tides in the Coastal Ocean  
Feb 27 Beth Scott U. of Aberdeen Marine renewable energy extraction, climate change and trophic linkages: What do we need to understand?  
Mar 6 Kathleen Dohan ESR 20 year trends in OSCAR surface currents  
Mar 13 Jody Klymak U. Victoria Observational Examples of Submesoscale Lateral Mixing  
TUES Mar 19 3:30 [SPECIALDATE/TIME] Matthew Hecht Los Alamos National Laboratories Response of Atlantic Circulation to Freshwater Perturbations in a Strongly Eddying Ocean Model  
Mar 20 Brian White UNC Chapel Hill Mass and energy exchange at coastal density fronts: mixing layers, gravity currents, and internal waves In stratified coastal waters, large horizontal density gradients are common. These horizontal gradients result in propagating density fronts, which produce vertical shear, turbulent mixing, and can even generate large amplitude internal waves. In this talk two specific examples of flows with horizontal density gradients are discussed. The first is a buoyant plume propagating into stratification, which under certain conditions undergoes a resonant interaction with internal waves at the plume front. This resonance can produce large waves that develop overturning circulation and contain mixed fluid. The second case involves the mixing of two water masses with large horizontal shear and horizontal density gradient. An example is tidal flow which separates at the boundary of an island wake. In this case, vertical vorticity due to the horizontal shear tilts under gravity, is stretched and intensified, and produces large vertical mixing. These examples are explored through a combination of Boussinesq Navier-Stokes simulations, laboratory experiments, and theory, with a focus on scaling, evolution of energy budgets, turbulent mixing, and hydraulic theory for stratified fluids.