IODP Survey of the "Shackleton Sites" on the Southwest Iberian Margin

Advances in our understanding of the Earth's climate system will rely on our ability to link high-resolution sedimentary archives from the oceans, ice-cores and terrestrial sequences, and to interpret these records in the context of novel Earth system modeling approaches. Few places exist in the world where sufficiently detailed and unambiguous marine-ice-terrestrial linkages are possible. One challenge for IODP, and the broader drilling community in general, is to identify and recover marine, ice and terrestrial sequences from appropriate locations and with adequate temporal resolution to study processes of the integrated climate system.

One such region is the southwest Iberian Margin where it has been demonstrated that the surface oxygen isotopic record could be correlated precisely to temperature variations (i.e., d18O) in Greenland ice cores. By comparison, the benthic d18O signal in the same core resembled the temperature record from Antarctica. Moreover, the narrow continental shelf and proximity of the Tagus River results in the rapid delivery of terrestrial material to the deep-sea environment off Portugal, thereby providing a record of atmospheric changes and permitting correlation of marine and ice core records to European terrestrial sequences. This is the only place in the ocean where such marine-ice-terrestrial correlations have been demonstrated unambiguously. It is therefore highly desirable to extend the Iberian Margin record to encompass the full range of Plio-Pleistocene glacial-interglacial cycles by drilling with the JOIDES Resolution (JR).

Towards this end, Proposal 771-Full was submitted to IODP by an international group of 16 proponents led by the UK. The proposal was well received and reviewed by the Science Steering and Evaluation Panel (SSEP), but the IODP Site Survey Panel (SSP) identified major inadequacies in the quality of the seismic data:

"The panel raised several concerns on the suitability of the submitted data with regard to its appropriateness, both to image the target properly and with regard to the site location. The panel also discussed the need for 2 high-resolution lines and considered that places where Mass Transport Deposits (MTDs) or closely spaced faults were present deserved these 2 high-resolution lines."

This proposal requests 25 days of ship time to collect the necessary seismic and sediment data needed to meet the SSP requirements and recommendations. Several "stand-alone" scientific objectives are also proposed related to the modern hydrography and sedimentary processes on the southwest Iberian Margin, and calibration of palaeoceanographic proxies used for reconstructing past changes in deep-water circulation. This value-added science will make effective use of ship time and contribute key information needed to interpret the downcore records to be obtained by IODP.

The primarily beneficiary will be members of the academic community who are engaged in IODP research, specifically millennial-scale climate variability in records from the Iberian Margin. The success of IODP is contingent upon grassroots efforts by the scientific community to propose the best science and identify the best places to drill on the ocean floor. As such, site survey is one of the most important activities of IODP and directly impacts the success of the program. The research proposed herein is directly relevant to the primary scientific objectives of the IODP Initial Science Plan. As such, the UK will benefit both through enhanced participation in the IODP and the results of the site survey will be important for the future program.

More importantly for knowledge exchange will be links to the community through the Sedgwick Museum at the University of Cambridge, which attracts in excess of 84,000 visitors per year, including over 100 school group visits. We will establish a general display on how ocean drilling contributes to the study of past climate change. We will take advantage of the media and education resources available through IODP, including web content, media kits, an audiovisual library, fun and games activities for children, core replicas, press releases, brochures and other public relations materials. We will also engage school children with hands-on learning activities.

We will disseminate the results of our research to the wide range of beneficiaries through public and academic talks, workshops and symposia, and conference papers. Key scientific results deemed important enough to be of widespread media interest will be disseminated via the University of Cambridge's Office of External Affairs and Communications and the UCL Media Relations Office.