Contents: conveners, program committee, objectives, format and schedule, field trip, expected participation, field of interest, conference dates, abstract submission, accommodations, registration fee, and further information.

AGU Chapman Conference on Abrupt Climate Change

Byrd Polar Research Center
The Ohio State University
Columbus, Ohio, USA
15–19 June 2009

Conveners

• Harunur Rashid, Byrd Polar Research Center, The Ohio State University, Columbus, Ohio
• Lonnie Thompson, Byrd Polar Research Center, The Ohio State University, Columbus, Ohio
• Leonid Polyak, Byrd Polar Research Center, The Ohio State University, Columbus, Ohio

Program Committee

• Henning Bauch, IFM-GEOMAR, Bremen, Germany
• Claire Waelbroeck, LSCE-CNRS, Paris, France
• Valerie Masson-Delmotte, IPSL/CEA-CNRS, Paris, France
• Larry Edwards, University of Minnesota, USA
• Ian Hall, School of Earth Sciences, Cardiff University, United Kingdom
• Ian Howat, School of Earth Sciences/BPRC, Ohio State University, USA
• Konrad Hughen, Marine Chemistry and Geochemistry, WHOI, USA
• Tom Marchitto, Department of Geological Sciences/INSTAAR, University Colorado, USA
• Antje Voelker, INETI, Portugal

Conference Objectives and General Description

The main objective of the proposed conference on Abrupt Climate Change is to bring together a diverse group of researchers who deal with paleo-proxy records such as ice cores, corals, marine sediments, terrestrial (lakes and speleothems) archives, and coupled ocean-atmosphere climate models to discuss recent advances in understanding the mechanisms of abrupt climate changes. Since the discovery of the Dansgaard-Oeschger events in Greenland ice cores and their subsequent cousins in the marine sediments of the North Atlantic, search for these abrupt, millennial-scale events across the globe has been intensified. A good compilation of these abrupt climate events are given by Voelker et al. (2002). Since then, the number of paleoclimatic records has increased with most Northern Hemisphere records showing teleconnections with the D/O cycles in Greenland. However, the evidence for the abrupt climate change from the Southern Hemisphere is not clear although there appears to be a one-to-one correlation of the new EDML records of Antarctica with Greenland.

Marine and terrestrial paleoclimate records from the Southern Hemisphere are sparse and do not have enough temporal resolution to characterize the relevant timescales of climate variability. The paleo-records from the northern tropics and subtropics mainly show concordant climate changes with those in the North Atlantic, while asynchronous and even anti-correlated phenomena are exhibited in records from the Southern Hemisphere. For example, the Indian and East Asian monsoon systems seem to correlate with the North Atlantic climate, whereas the South American monsoon seems to operate differently. Furthermore, paleo-proxy records from the equatorial Pacific are characterized by a complex pattern of abrupt climate change that borrows elements from both the Northern and Southern Hemisphere end-members.

Three mechanisms were invoked to explain these abrupt climate changes: (a) freshwater forcing in which meltwater input from the circum-North Atlantic ice-sheets disrupts the meridional overturning circulation (MOC) by preventing the formation of North Atlantic Deep Water (NADW) in the Nordic seas; (b) sea-ice extent in which the albedo effect through altering the local and global energy and thus insulating the ocean from the atmosphere by cutting off the heat and moisture supply; and (c) tropical forcing which calls for a combination of the orbital configuration, El Niño-Southern Oscillation (La Niña) and sea-surface temperature (SST) conditions.

A number of outstanding scientific questions regarding Abrupt Climate Change include:

• Given the amount of attention focused on meltwater forcing in modulating the MOC from the circum-North Atlantic, to what degree and with what level of confidence do paleo-proxies suggest a one-to-one relationship between the freshwater fluxes and the strength of the MOC, as well as the sources of meltwater pulses?
• Are kinematic and nutrient proxies for the strength of the MOC congruent across the Abrupt Climate Changes?
• Do current GCM's simulate abrupt strengthening and gradual weakening of thermohaline circulation (THC), consistent with the rapid warming and gradual cooling of D/O events? If not, what other factors need to be considered other than the THC?
• Is there robust evidence for sea-ice in the Atlantic Ocean during the last glacial cycle? How much has sea-ice extent fluctuated on millennial-time scales? How has the fluctuations influenced the surface salinity and thus the density and water-mass stratification?
• With the exception of the tropical Atlantic marine record, most tropical paleo-records show a clear lack of D/O cooling. Does this indicate that the parts of the tropics respond differently due to ensuing changes in the hydrological cycles and temperature nested in the THC?
• Given the dramatic changes in Arctic sea-ice and hydrography, how did the Arctic freshwater budget affect the overturning circulation of the North Atlantic?
• Why does the Antarctic temperature show a more gradual and less pronounced warming and cooling compared to the D/O events in Greenland? Does this indicate a direct role for deep ocean circulation in ushering the abrupt climate changes?
• In light of the current concern about the instabilities of the West Antarctic and Greenland Ice Sheets how can paleoceanographic records be used to decipher past ice-sheet dynamics?
• What is the link between sea-ice extent and ice-sheet dynamics?
• What are the climate tipping points that have driven past civilizations to collapse?

We invite contributions dealing with any aspect of Abrupt Climate Change, including the numerical models which incorporate proxy records as well as idealized models. Abstracts are solicited for any topic relevant to the above or other questions relating to Abrupt Climate Change.

A Chapman conference is uniquely suited to fruitful discussion of existing records, strategies to acquire new records and research priorities, and of crosscutting science issues: a group of manageable size that includes observational and modeling expertise across sub-disciplines rarely occurs in any other venue.

Format and Schedule

The meeting will span five days, with Friday afternoon off (see below for the planned field trip). The schedule is designed to maximize discussion and debate opportunities, and to make the meeting approachable to a broad audience. Each meeting day will consist of a morning and afternoon session, beginning with a keynote lecture, then continuing with two sessions on each of the main focus areas:

1. Ice cores records from both poles and high altitudes
2. Marine records from pole to pole
3. Marine and terrestrial proxy records of abrupt climate change
4. Coupled climate models and their performance in simulating abrupt climate change
5. Abrupt climate change and collapse of past civilizations

The meeting will finish with a closing session to sum up the meeting and consider future directions. Each session from 1-5 above will include four invited talks (speakers TBA) to introduce the key issues, followed by open discussions moderated by the program committee, and brief poster presentations. There will be one poster session per day for other attendees to present their work except on Friday.

Field Trip

Friday trip to the end moraine and Torren Bogs of the southeastern Ohio, by Professor Garry Mackenzie of the School of Earth Sciences, The Ohio State University, is planned. Details to follow.

Expected Participation

100-150 including 25-35 graduate students. Support is anticipated for some postdocs and graduate students; details to follow.

Fields of Interest

Abrupt climate change, freshwater forcing, meridional overturning circulation, sea-ice and their impact in abrupt climate change, ice cores, paleo-monsoon, paleo-ENSO, ice-sheet dynamics, climate system and theory, general circulation models, and collapse of the past civilization.

Conference Dates

15-19 June 2009

Abstract Submission

Abstract Submission Deadline: 20 March 2009
Please follow the abstract submission instructions (.doc).

Attendance and participation in the workshop is based on selection of first-authored abstracts by the program committee; selection will be on a competitive basis and will take place a few weeks following the submission deadline.

Accommodations

Details to follow.

Registration Fee

Details to follow.

Registration Deadline

Details to follow.

Further Information

If you would like to receive future updates about this conference, e-mail chapman-abruptclimate@agu.org, or call the AGU Meetings Department at +1-202-777-7330. For information about the scientific program, please contact one of the conveners via e-mail:

Harunur Rashid
Byrd Polar Research Center
The Ohio State University
Columbus, Ohio
rashid.29@osu.edu

Lynn Everett
Byrd Polar Research Center
The Ohio State University
Columbus, Ohio
everett.2@osu.edu

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© 2009 American Geophysical Union

updated 26 November 2008