[Eoas-seminar] Meteorology MS Defense for Brian Haynes, October 31, 3:30 PM, Love 353

[eoas-seminar at lists.fsu.edu]

Meteorology Seminar

Brian Haynes

MS Meteorology Candidate



Title:  Climate Variability of the Arctic from an Isentropic Potential Vorticity Perspective

Major Professor:  Dr. Eric Chassignet

Date: October 31, 2019                           Time: 3:30 PM



Location: Werner A. Baum Seminar Room (353 Love Building)
(Please join us for refreshments served outside room 353 Love @ 3:00 PM)

ABSTRACT


The persistence of the positive phase of the Arctic Ocean Oscillation (AOO) during the last two decades is examined by invoking potential vorticity dynamics in a warming Arctic climate to describe tendencies of atmospheric forcing at the Arctic boundary layer.  Positive indices of the AOO are indicative of an anti-cyclonic wind stress being imparted at the ice-ocean surface in the Beaufort Sea, a pattern typical during Arctic winters, throughout most of a given year.  An IPV framework used to relate increasing Arctic ambient temperatures and sea ice loss with the AOO is achieved by analyzing isentropic output from a blend of the Climate Forecast System Reanalysis (CFSR) and Climate Forecast System version 2 (CFSv2) reanalysis data, as well as surface heat flux output from the same dataset in order to draw conclusions about how diabatic effects may annihilate low-level potential vorticity and reinforce atmospheric stability. These analyses were sectioned into a focus of the inherent differences between positive and negative (cyclonic-regime) phases of the AOO over the time period spanning 1979-2017, with a closer examination pertaining IPV advection and baroclinic development during differing AOO cycles in the Arctic on synoptic timescales.



The trends and patterns in Arctic IPV are compared with Arctic sea ice extent and linked to warming by a reduction in the meridional IPV gradient, which in turn weakens the zonal flow and allows for the meridional advection of lower potential vorticity into the region.  Baroclinic development of these disturbances vary in location and with season and can amplify ridging downstream, enhancing stationary waves.  This implies not only a connection between reduced IPV and the negative phase of the Arctic Oscillation (AO), but that the weakened IPV gradient may allow for transmittance of heat and momentum to the upper levels of the atmosphere, supporting previous studies regarding the impacts that wave-mean flow interaction has on the warming tropopause. These findings demonstrate that the ice melt season, specifically summer and autumn, has an important role in determining the AOO cycle and are supported by IPV theory.




Shel McGuire
Florida State University
Academic Program Specialist
Department of Earth, Ocean, & Atmospheric Science
1017 Academic Way, 410 Love Building (Meteorology)
Tallahassee, FL 32306
850-644-8582

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