[pccgrads] GSS tomorrow at 5pm in OSB 425: Judy Twedt

Hilary Palevsky palevsky at u.washington.edu
Mon Nov 30 09:37:02 PST 2015

Hello PCC grads!
The final installment of the fall quarter Graduate Student Seminar
will be *this
Tuesday (tomorrow), December 1 at 5pm in OSB 425*! *Judy Twedt* from
Atmospheric Sciences will be presenting on "Assessing the Link between
Tropical Pacific Variability, Global Warming, and Antarctic Climate Change
in CESM 1.1." Check out the full description below!

Also, we will soon be setting up the schedule for the winter quarter GSS to
begin in January, so if you are interested in presenting, email me, Brad (
marklebr at uw.edu) or Greg (gquetin at uw.edu) to let us know!

Hope to see many of you tomorrow!

Hilary, Brad and Greg

*This week's talk:*
Judy Twedt (Atmospheric Sciences) "Assessing the Link between Tropical
Pacific Variability, Global Warming, and Antarctic Climate Change in CESM

The recent expansion in Antarctic sea ice and the reported hiatus in global
warming are at odds with CMIP5 model responses to anthropogenic forcing.
Many studies have looked to the cooling of the central and eastern Tropical
Pacific from 1980 - 2013 as potential drivers of these unexpected trends,
via Rossby wave teleconnections and increased ocean heat uptake in the
subtropical Pacific. Rossby waves emanating from the tropical Pacific are
known to impact high latitudes, but their role in the recent expansion of
Antarctic Sea ice is still a subject of debate. Furthermore, the
wind-driven cooling of the tropical Pacific may change the rate of surface
warming through an increase in ocean heat uptake, thus the Pacific may also
be causing the reported hiatus. We test both of these hypothesis in two
experiments carried out with a coupled ocean-atmosphere model, the
Community Earth System Model 1.1. The first method uses an energy
conserving flux adjustment to reproduce the observed cooling in the central
and eastern tropical Pacific. The second method introduces a new tool to
CESM; it adds an anomalous wind stress to the tropical Pacific while
preserving the atmosphere-ocean coupling.

We find that both forcing methods are able to simulate a cooling trend in
the tropical Pacific and the attendant changes in tropical convection. Yet
neither method reproduces a slowdown in global warming. Furthermore, the
teleconnections to Antarctica show a modest effect on sea ice extent, but
do not fully account for the recent expansion in Antarctic Sea Ice.

Bonus: (time permitting) I will also present some results from idealized
experiments with a slab ocean model in which teleconnections are simulated
through atmospheric heating anomalies. These experiments use prescribed
ocean dynamics and thus isolate the role of atmospheric forcing on sea ice.

*What is the GSS, you ask?*
The PCC Graduate Student Seminar (GSS) is organized by graduate students
for graduate students. The series provides an extremely laid back
environment where grad students give 25-35 min presentations on their
research followed by a 20 minutes of questions/discussion on the topic.
It's a great opportunity to see what is going on in climate research with
your fellow students down the hall or across campus. Plus, it you are
interested in presenting, it's a great chance to show off some of your own
research and receive feedback on your work. Presentations should be geared
toward a general scientific audience (of graduate students) with ample
background information so everyone can follow. As always, *be*v*er*ages
will be provided for a minimal donation.

<00>< <00>< <00>< <00>< <00><
Hilary Palevsky
PhD Candidate, Chemical Oceanography
University of Washington
School of Oceanography
Email: palevsky at u.washington.edu
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