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1: Improve knowledge and understanding of past polar climate variations (100+ years)

Co-leads: Sarah Gille (Scripps Institution of Oceanography, USA) and Julie Jones (University of Sheffield, UK)

The goal of theme 1 is to understand changes in the polar regions that are occurring and the processes behind them by considering a variety of resources that are available from the last century and longer in a unified, multi-disciplinary way. Theme participants will bring together estimates of past behavior in the polar regions, such as instrumental and proxy data records, modeling, and reanalyses techniques, in an optimal manner, to obtain estimates of past variability and change. These efforts can also help in the design of optimized observing systems for detecting and attributing changes, and quantifying the impact of maintaining or obtaining certain observations. We intend to identify new data records of the 20th century that have recently become available, which are especially important in the presatellite era. Models can potentially be used to enhance state reconstructions through forward data simulations.

Within this broader framework, this theme seeks to identify focussed research questions that can be successfully addressed in the near term through a concerted coordinated effort, to avoid it being a pure data-gathering exercise (as it is important to write publications as part of this theme).

Initial ideas for research questions/areas (initially focussed rather more on Southern Hemisphere due to interests/expertise of the leads, until a third lead may be found):
-    Use of mid-latitude surface pressure data to reconstruct Antarctic station pressures.  Can other data fields, such as sea ice concentration or sea surface temperature, lead to an improvement in Antarctic surface pressure reconstruction or be used for consistency tests?
-    Why is sea ice changing?  Is there evidence that trends in the sea ice are linked to other components of the system? Why are sea ice changes different at the two poles?
-    How annular is the annular mode and does its spatial structure change over time?
-    Can we reconstruct the Amundsen-Bellingshausen Sea Low (ABSL)?  

Possible next steps

-    Identify initial ‘straw man’ research questions.  Defining these questions will help identify core areas (and hence people who we would like to ask to play a role in the theme)
-    Run these questions past other relevant people already involved in PCPI
-    Refine these questions
-    Contact people who we would like to be involved
-    To potentially identify a 3rd co-lead with expertise of Arctic Climate, as neither current co-lead has strong knowledge of this region

We anticipate that much contact would be through teleconferencing/Skype, as our colleagues generally have many commitments, and may be more likely to agree to something that does not involve extensive travel.  We also plan to utilise meetings of opportunity, but given the disciplinary breadth of the community that would be involved (atmosphere, ocean, sea ice, Arctic, Antarctic), it may be more difficult to find meetings where all attend.  (However, sub-working groups may find that they can take advantage of meetings of opportunity.)