Workshop on Holocene climate variability off Wilkes Land, East Antarctica

• Organizers: Johan Etourneau, Carlota Escutia, Rob McKay & Nancy Bertler

• Contact person: This email address is being protected from spambots. You need JavaScript enabled to view it.

• Participants: Etourneau, C. Escutia, R. Mckay, N. Bertler, X. Crosta, F. Jimenez Espejo, F. Sangiorgi, J. Hartman, K. Newton, B. Stenni, L. Sim, L. de Santis, B. Khim, J. Kim, L. Eking, A. Uv, K. Johnson, D. Lowry

• Day: Saturday 16^th, from 8:00-13:00 and 13:30-16:45

• Aim of the workshop:

Current understanding of Antarctic climate changes over the last deglacial warming period and the Holocene, as the baseline of the current global warming, mainly relies on ice cores that provide a synoptic view of atmospheric processes. Very few marine records exist, all of them with a much lower resolution than ice cores. Consequently, our knowledge of Antarctic Ocean evolution at the decadal resolution, at which the global warming affects ocean circulation, environmental conditions and ecosystems, is therefore extremely poor. The international IODP 318 “Wilkes Land Glacial History” expedition retrieved unique laminated sedimentary sequences with the goal of understanding the last ~12,000 years BP at seasonal to decadal timescales. The aim of the workshop is to bring scientists working on these archives in order to better constrain sedimentary records using novel methods for dating and monitor past changes in regional sea-ice, primary productivity (phytoplankton) and biogeochemical cycles via a series of new and traditional proxies, including a data-model comparison. Due to innovative (but complex) approaches, there is a crucial need to physically face the data and improve models by sharing complementary expertise. This workshop provides a rare opportunity to organize such a meeting with the final objective to produce several major publications in highly ranked journals and to prepare proposals on future joint research by involving both marine and continental (ice core) community as already initiated in the framework of the ESF PolarClimate HOLOCLIP project (2010-2012).

• Program:

8:00-8:15 - Introduction: J. Etourneau & C. Escutia

8:10-9:10 - Stratigraphy (grainsize, CT scans, image analysis), age model, and geochemistry: R. Mckay, R. Dunbar, C. Riesselman, A. Albot, Katelyn Johnson

9:10-9:45 - Palynology and TEX86-based sea-surface temperatures from the Adélie coastal margin: J. Hartman, V. Wilmott, F. Sangiorgi, P. Bilj, S. Schouten, H. Brinkhuis

9:45-10:30 - Compound-specific carbon and hydrogen isotope analysis of fatty acid biomarker: K. Newton, O. Seki, J. Bendle

10:30-10:45: Coffee break

10:45-11:00 - Biogenic opal productivity and Holocene paleoclimate in the Adelie Basin (IODP Exp. 318 Hole U1357A): B.K. Khim, J. Kim & R. Dunbar

11:00-11:25 - Holocene deglaciation of the East Antarctic margin: F. Jimenez-Espejo, C. Escutia, X. Crosta, J. Etourneau, G. Massé

11:25-12:00 - Sedimentary material and data available in the Adélie Land region: X. Crosta, P. Campagne, J. Etourneau, G. Massé

12:00-12:20 - A novel approach to monitor climate changes in Wilkes Land, East Antarctica, over the last 2,000 years - J. Etourneau, C. Yoshikawa, P. Campagne, M.-N. Houssais, N.O. Ogawa, F. Jimenez Espejo, H. Suga, I. Bouloubassi, C. Escutia, G. Masse, X. Crosta, N. Ohkouchi

12:20-12:25 - Deep Antarctic ice cores – Holoclip data base: Stenni et al.

12:25-13:00 - Wind driven Ocean/Ice Interactions during the Ross Sea region deglaciation: N. Bertler et al.

13:00-13:30 - Lunch break

13:30-15:00 - Discussions between ice core and marine communities: future work, strategy, workshops, proposals

15:00-16:30 - Discussions about Wilkes Land: The Holocene, the deglaciation and the last 2,000 years BP

16:30-16:45 - Close up

• Presentation and discussions

The oral presentations were divided in two parts: 1) the marine cores from the Wilkes Land area (i.e the IODP Site U1357 and MD03-2601) and 2) the ice cores related to the RICE and HOLOCLIP projects. During this workshop, we were able to face for the first time both atmospheric and oceanic conditions at nearly the same time resolution throughout the deglaciation, the Holocene and the last 2,000 years as very high sedimentation rates characterized the marine archives, thus allowing annual to multi-annual reconstructions. Moreover, new or recently developed biomarkers (e.g. dD of fatty acids, high branched isoprenoids (HBI), d¹⁵N of chlorins, TEX86-L) have been combined in the marine sections to more traditional proxies such as those used in micropaleontology (e.g. diatoms, palynology), geochemical (e.g. d¹⁸O of pore waters, biogenic opal, total organic carbon and nitrogen) and sedimentology (e.g. grain size and XRF), thus allowing a direct comparison of marine records with those generated on the continental ice cap. For instance, it has been evidenced that the Mertz polynya activities seem to be, similarly to nowadays, strongly connected to the Ross Sea climate and environmental conditions.

One of the greatest challenges discussed during the workshop is how to improve the integration of the marine and ice cores data and the comparison with models. As an example, we might compare Na records in the ice cores and sea ice-related proxies in marine sequences to link the oceanic conditions with the atmospheric circulation. To further enhance such kind of collaboration between the two communities, especially between the two groups targeting similar objectives, we proposed to create a webpage where all the published and unpublished data generated so far by the different groups could be shared. In this way, we could be more easily in contact with those who provided data for a specific study. In particular, a topic could be related to the 8.2 kyrs event where everyone involved in this joint and coordinated effort could have access to the database and use it in concert with the respective people to better understand such climatic event. Another point addressed during this workshop concerns the “wish list” of both communities regarding the data. Meltwater fluxes, Antarctic Bottom Water formation, Circumpolar Deep Water intrusion and polynya activity are of great interest for the ice core community. Conversely, atmospheric circulation, air temperature variations, precipitations and reconstructions of air-sea exchange are of primary importance for the marine community. Moreover, better-dated ice cores could be used to better constrain the chronology of deglaciation when marine cores meet some difficulties. Therefore, there is a strong need to improve discussions so that once all these marine and continental data are compared, they can also be very helpful for improving modeling studies. The main challenge in the very near future is therefore to design the merging of marine and ice core data from different teams. Sharing students, applying for SCAR fellowship and finding financial support for networking is fundamental to strengthen this necessary collaboration. To maintain this effort, we propose to organize a side meeting at the POLAR 2018 conference in Davos where the next XXXV SCAR Biennial meeting will take place. We thus hope to reinforce the international collaborations and resolve some of the main issues regarding past climate variability.