Introduction

Sea ice is a key research focus of the CliC Project, and a core element of new efforts of WCRP to enhance credibility of Arctic climate prediction and projection. Observations indicated that Arctic sea ice has become one of the most rapidly changing components of the global climate system. Due to its nature, sea ice is much more sensitive to variations in external forcing than other climate system components, and it integrates the interdependent processes of the global energy and water cycles. Changes in sea ice also feed back into the overlying atmosphere and the underlying ocean, with the potential to further amplify environmental change as a system, impacting ecosystems and societies. Understanding present arctic sea ice conditions, its predictability and projecting future changes have therefore become central pieces of current climate studies.

The most prominent recent changes observed in arctic sea ice is the accelerating decrease in sea ice cover since the mid-1990s including the extreme loss of summer sea ice cover in 2007. Understanding this phenomenon would be a key to untangling the complex problem of rapid sea ice change and would enhance the credibility of future sea ice change projections. Existing studies have attributed such rapid changes to various factors including greenhouse-gas-emissions forcing, intensification of the North Atlantic and North Pacific warm water intrusion, shifts of atmospheric circulation and increases in poleward atmospheric heat transport, sea ice-induced albedo feedback and cloud-modulated and forced surface shortwave and longwave radiation, as well as preconditioning by wind-driven sea ice export. However, the fundamental driving forces behind these contributing factors and their relative importance have not been quantified. A coordinated effort to integrate the current state-of-knowledge and to conduct a synthetic analysis about the recently observed rapid sea ice change and its future occurrence are pressing needs. This effort falls well within the recommended research areas described in the recent WCRP White Paper (WP) and will help coordination of the forthcoming CMIP5 activities.

Objectives

This workshop had four objectives:

• To synthesize the state-of-knowledge and assess the leading drivers of systematic changes in Arctic sea ice cover, including triggers and terminators of rapid change episodes (RaCE), and mechanisms that could aid intermittent or longer-term recovery of the perennial ice pack.
  
  
• To assess the role of the rapid sea ice change episode in influencing the ice cover's future trajectory over interannual to decadal and century time scales and in determining the timing of a seasonally ice-free Arctic Ocean.
  
  
• To determine the large-scale atmospheric and oceanic consequences of the rapid sea ice loss.
  
  
• To identify knowledge gaps and provide suggestions/recommendations for observational campaigns and for coordinating the forthcoming CMIP5 research activities.

Participants and Workshop Location and Date

This workshop took place at IARC from 6-8 Oct. 2010, bringing together 35 experts in both observations and model simulations from the areas of sea ice, atmosphere, and ocean. Participants included:

Agnieszka Beszczynska-Möller (AWI/Germany)	- ocean
Uma Bhatt (GI)	- atmosphere
Cecilia Bitz (UW)	- sea ice
Eddy Carmack (IOS/Canada)	- ocean
Joey Comiso (NASA)	- sea ice
Hajo Eicken (GI/IARC)	- sea ice
Ian Eisenman (Caltec)	- sea ice
Sebastian Gerland (NPI/Norway)	- sea ice
Rune Grand Graversen (Stockholm/Sweden)	- atmosphere
Larry Hinzman (IARC)	- director
Masahiro Hori (JAXA)	- sea ice
Kay Huebner (MPI-M/Germany)	- ocean
Jenny Hutchings (IARC)	- sea ice
Vladimir Kattsov (Russia)	- atmosphere
Jennifer Kay (NCAR)	- atmosphere
Yinghui Liu (U. Wisconsin/NOAA)	- atmosphere
Alexander Makshtas (AARI/Russia)	- atmosphere
Svein Østerhus (BCCR/Norway)	- ocean
Jim Overland (NOAA)	- atmosphere
Don Perovich (CRREL)	- sea ice
Igor Polyakov (IARC)	- ocean
Ignatius Riger (APL/UW)	- sea ice
Andrew Roberts (IARC)	- sea ice
Joao Rodrigues (Cambridge/UK)	- sea ice
Julienne Stroeve (NSIDC)	- sea ice
Adrienne Tivy (IARC)	- sea ice
Steve Vavrus (U. Wisconsin)	- atmosphere
John Walsh (IARC)	- atmosphere
Muyin Wang (PMEL/NOAA/UW)	- atmosphere
Eiji Watanabe (IARC)	- ocean
Mike Winton (GFDL/NOAA)	- sea ice
Daqing Yang (CliC)	- arctic climate
Jinlun Zhang (APL/UW)	- sea ice
Xiangdong Zhang (IARC)	- atmosphere
Jinping Zhao (OUC/China)	- ocean

Expected Outcomes

We anticipate that the workshop will help the community of sea ice and climate modelers and observationalists to understand the nature of changes that the Arctic sea ice cover has been undergoing over the past few decades and in the state-of-the-art climate model simulations and projections, to identify research and observation needs and next steps that should be taken to improve projections of future sea ice changes on interannual to decadal and century timescales, and to put into perspective interannual variability relative to secular and long-term externally forced changes.

We plan to develop a review/synthesis paper wrapping up workshop outcomes. The tentative target of the publication will be the Bulletin of the American Meteorological Society or EOS.

Organizers and Sponsorship

The organizing committee consisted of experts representing the core constituencies and sponsorship for the meeting, including IARC, the CliC Arctic Sea Ice Working Group, and the CliC and WRCP Programs. The members include:

Xiangdong Zhang (IARC/UAF), Hajo Eicken (UAF/CliC), John Walsh (UAF), Sebastian Gerland (NPI/CliC), Vladimir Kattsov (MGO/Russia/WCRP), Greg Flato (CCCMA/Canada/WCRP), Eddy Carmack (IOS/Canada), Daqing Yang (CliC).

Agenda

Wed Oct 6, 2010

09:00 - 10:00 AM: Introduction (Convener: Xiangdong Zhang)

Welcome by IARC director (Larry Hinzman) and CliC Office director (Daqing Yang)
John Walsh: Workshop overview by the organization committee
Vladimir Kattsov: WCRP White Paper
Daqing Yang: Climate and Cryosphere (CliC) Project: an update
Sebastian Gerland: CliC Sea Ice Working Group

10:00 - 10:20 AM: Break

10:20 - 11:50 AM: Oral presentation I (Convener: Eddy Carmack)

Focal topic: Rapid changes in sea ice mass balance: Multi-scale observations from satellites, field experiments, and proxy data; recent rapid changes in historical context

10:20 - 10:50 AM:	Josefino Comiso: The Rapidly Shrinking Arctic Multiyear Ice Cover
10:50 - 10:20 AM:	Sebastian Gerland: Examples from sea ice observations north of Svalbard with relevance for satellite remote sensing
10:20 - 11:50 AM:	Hajo Eicken: Recent changes in the sea ice mass balance in the Beaufort and Chukchi Sea
11:50 - 12:20 AM:	Joao Rodrigues: Recent measurements of Arctic sea ice thickness from U.K. submarines
12:20 - 12:50 AM:	Jinping Zhao: Low ice concentration appeared in central Arctic of 2010 and the physical explanation

12:50 - 1:00 PM: Lunch

1:00 - 3:30 PM: Oral presentation II (Convener: Hajo Eicken)

Focal topic: Changes in large-scale atmospheric and oceanic circulations, including wind forcing and heat transport, and their roles in driving sea ice mass balances and imbalances

1:00 - 1:30 PM:	Eddy Carmack: Perspectives on the underlying ocean
1:30 - 2:00 PM:	Svein Osterhus: Poleward propagation of oceanic heat anomalies
2:00 - 2:30 PM:	Igor Polyakov: Recent changes of arctic multiyear sea-ice coverage and the likely causes
2:30 - 3:00 PM:	Agnieszka Beszczynska-Möller: Oceanic heat flux through Fram Strait: a potential link between North Atlantic conditions and recent changes of the Arctic sea ice?
3:00 - 3:30 PM:	Julienne Stroeve: Sea ice response to an extreme negative phase of the Arctic Oscillation during winter 2009/2010

3:30 - 4:00 PM: Break

4:00 - 05:30 PM: Discussion I (Conveners: Eddy Carmack and Hajo Eicken)

Focal topic: Observational gaps (what is crucial but not available; inter-product scatter and causes; expectations for observing systems in the near future)

4:00 - 05:30 PM: 6:00 - 7:30PM: Poster presentations (Moderated by Xiangdong Zhang)

All participants

Thurs Oct 7, 2010

9:00 - 10:30 AM: Oral presentation II (Convener: Sebastian Gerland)

Focal topic: Changes in large-scale atmospheric and oceanic circulations, including wind forcing and heat transport, and their roles in driving sea ice mass balances and imbalances

9:00 - 9:30 AM:	Rune Grand Graversen: On the linkage between atmospheric circulation changes and Arctic sea-ice melt
9:30 - 10:00 AM:	Ignatius Rigor: Interdecadal Variations in Arctic Sea Ice
10:00 - 10:30 AM:	Jennifer Kay: Does poleward heat transport affect Arctic amplification?

10:30 - 11:00 AM: Break

11:00 - 12:00 AM: Oral presentation II (Convener: Sebastian Gerland)

11:00 - 11:30 AM:	Adrienne Tivy: Exploring atmospheric and oceanic forcing of inter-annual variability in summer sea ice extent in observations using canonical correlation analysis
11:30 - 12:00 AM:	Xiangdong Zhang: Atmosperhic circualtion's driving role in the recent rapid changes in sea ice

12:00 - 1:00 PM: Lunch

1:00 - 3:30 PM: Oral presentation III (Convener: Daqing Yang)

Focal topic: Physical processes including scale-interactions, cloudiness, radiative forcing, turbulent heat flux, ocean mixing

1:00 - 1:30 PM:	Don Perovich: The sea ice albedo feedback in a changing Arctic
1:30 - 2:00 PM:	Steve Vavrus: Arctic Cloud Changes during Intervals of Rapid Sea Ice Loss
2:00 - 2:30 PM:	Muyin Wang: Melting pond in the Arctic Sea ice: How much can we learn from the NPEO?
2:30 - 3:00 PM:	Yinghui Liu: Understanding the Interactions and Feedbacks Between Arctic Sea Ice, Clouds, and the Atmosphere from Satellite Observations
3:00 - 3:30 PM:	Andrew Roberts: Multiscale mechanics metrics to aid understanding of changes in the Arctic sea ice cover

3:30 - 4:00 PM: Break

4:00 - 5:30 PM: Discussion II (Conveners: Sebastian Gerland and Daqing Yang)

Focal topic: Gaps in understanding processes and feedbacks (scales; climate system component interactions; etc.)

6:00 - 8:00 PM: Chapman Chair lecturer Ian Eisenman:

Changes in the sea ice seasonal cycle in response to climate change

Continued discussions II with lecture audience (Convener: Eddy Carmack)

Fri Oct 8, 2010

9:00 - 10:30 AM: Oral presentation IV (Convener: John Walsh)

Focal topic: Large-scale atmospheric and oceanic feedbacks and consequences

9:00 - 9:30 AM:	James E. Overland: Hot Arctic-Cold Continents: Climate Impacts of the Newly Open Polar Sea
9:30 - 10:00 AM:	Masahiro Hori: A study on recent summer atmospheric impacts on the Arctic sea-ice variation and brief overview of JAXA's activities for the Arctic researches
10:00 - 10:30 AM:	Uma Bhatt: What drives recent Arctic tundra vegetation changes?

10:30 - 11:00 AM: Break

11:00 - 12:00 AM: Oral presentation V (Convener: John Walsh)

Focal topic: Rapid changes in model simulations and projections including model performance, sensitivity, and predictability

11:00 - 11:30 AM:	Cecilia Bitz: Arctic sea ice projections in the CCSM4
11:30 - 12:00 AM:	Mike Winton: Do climate models underestimate the sensitivity of Arctic sea ice?

12:00 - 1:00 PM: Lunch

1:00 - 3:30 PM: Oral presentation V (Convener: Vladimir Kattsov)

1:00 - 1:30 PM:	Alexander Makshtas: Model estimations of sea ice conditions in the Arctic Basin at the end of XX and XXI century
1:30 - 2:00 PM:	Jinlun Zhang: Hindcast and Future Projections of Summer Arctic Sea Ice: 1978-2050
2:00 - 2:30 PM:	Kay Huebner: Impact of Snow on Sea Ice Growth

2:30 - 3:00 PM: Break

3:00 - 4:00 PM: Discussion III (Conveners: John Walsh and Vladimir Kattsov)

Focal topic: Shortcomings and limitations of state-of-the-art models (particularly AOGCMs) including issues of model evaluation and discrimination, initialization, assimilation, etc.

Predictability of sea ice on different time scales (in a wider context of the polar climate predictability). Potential uses of models in charting the trajectory of sea ice.

All participants

4:00 - 5:30 PM: Reports, Workshop Summary, and Plan for Review Paper (Convener: Xiangdong Zhang, John Walsh and Vladimir Kattsov)

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