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Department of Estuarine and Ocean Sciences Seminar Announcement

When: Wednesday, December 2, 2015
12:30 PM - 1:30 PM
Where: > See description for location
Description: The School for Marine Science and Technology
Department of Estuarine and Ocean Sciences
Seminar Announcement

"On the Processes Controlling Antarctic Dense Shelf Water Outflows"

Gustavo M. Marques
Postdoctoral Research Associate
Princeton University

Wednesday, December 2, 2015
12:30 pm - 1:30 pm

SMAST I, Room 204
706 S. Rodney French Blvd., New Bedford, MA

Abstract:
Formation of intermediate and abyssal water masses as dense water flows off continental shelves contributes to the lower limb of the meridional overturning circulation. This talk will be focused on two previously unknown processes that may influence the volume flux and physical properties of dense shelf water outflows around Antarctica. First, idealized and realistic numerical simulations will be used to show that Antarctic outflows can excite topographic vorticity waves (TVWs). The modeled waves are sufficiently energetic to play an important role in cross-slope water mass exchanges and Antarctic Bottom Water production. The wave frequency depends on the amount of stretching in the ambient fluid over the outflow and on the background along-slope mean flow. Frequency is higher for steeper bottom slope, larger outflow density anomaly, and stronger westward mean flow. For weak stratification and weak westward along-slope flows typical of the Antarctic slope, wave energy propagates eastward, in the opposite direction from phase velocity. These findings are consistent with recent observations of TVWs in the southern Weddell Sea and with a realistic simulation of the Ross Sea. Second, high-resolution numerical simulations that reveal flow splitting in oceanic outflows will be presented. Flow splitting, previously observed in laboratory studies, carry water properties from the shelf into the deep ocean at distinct depths. An important characteristic of this regime is the flow transition from a supercritical condition, where the Froude number (Fr) is greater than one, to a slower and more uniform subcritical condition (Fr < 1). This transition is associated with an internal hydraulic jump and consequent mixing enhancement. The parameters needed to identify this flow regime will be discussed. These results are the first evidence that flow splitting may occur in oceanic environments, such as the Antarctic outflows.


Note: Seminar will be simulcast to SMAST II, Room 325.

You can view the seminar live by clicking
here: "live event" . Please note: the earliest you will be able to log in is
15 minutes before the regularly scheduled time.


To view a video of an SMAST seminar (post-October 1st), go to http://www.umassd.edu/smast/newsandevents/seminarseries/ and click on a highlighted title.

For additional information, please contact Sue Silva at s1silva@umassd.edu
Contact: > See Description for contact information
Topical Areas: SMAST Seminar Series