INTIMATE 1995 to 2009

At a Workshop Session following the NASP Symposium, the INTIMATE programme was formally established, with John Lowe as Project Co-ordinator and Mike Walker as Secretary. INTIMATE was designed to encourage collaboration between the ice-core, marine and terrestrial communities that had begun during the later stages of the NASP programme, and to integrate the increasing number of high-resolution proxy climate records from the Last Termination that were becoming available from different parts of the North Atlantic realm. The aim was also to underpin the proxy records for climate change with high-resolution chronologies, and to correlate key events in order to determine leads and lags in the climate system during the Last Glacial-Interglacial Transition (LGIT).

Organisation of INTIMATE 1995-2009

INTIMATE was organised through a Secretariat involving the Co-ordinator, Secretary, and a Steering Group. The Co-ordinators have been John Lowe (1995-2003), Wim Hoek (2003-2008) and Chris Turney (2008-2010). The Secretary’s position has been held by Mike Walker (1995-1999), Wim Hoek (1999-2003), and Zicheng Yu (2003-2008). The first Steering Group was appointed at the Hoor Workshop in 1997 (see below), and was composed of John Lowe and Mike Walker (ex-officio), Sigfus Johnsen (ice core community), Karen-Luise Knudsen (marine community), Svante Bjorck and Barbara Wohlfarth (terrestrial community: Europe) and Les Cwynar (terrestrial community: North America). In 2003 following the Reno Workshop at the XVIth INQUA Congress, and in response to the expanded remit of INTIMATE (see below), a new Steering Group was appointed, with Wim Hoek and Zicheng Yu as ex-officio members, seven regional co-ordinators (Svante Bjorck - Northern Europe; Thomas Litt - Central Europe; Sjoerd Bohncke - Western Europe; Blas Valero-Garces - Southern Europe; Les Cwynar - North American Atlantic Seaboard; Fabienne Marret - African Atlantic Seaboard; Karen-Luise Knudsen -Northern Atlantic/GIN Seas; Gerard Bond – Atlantic Marine Records; Sigfus Johnsen and Jorgen-Peder Steffensen – Ice-core Records (GRIP); Pieter Grootes; Ice-core records (GISP2); Bernd Kromer - Radiocarbon calibration; Siwan Davies - Tephrochonrology; and Hans Renssen - Palaeoclimatic modelling. Sadly Gerard Bond passed away on 29th June 2005. He had been active in INTIMATE since the start of the project, was a keynote speaker at the INTIMATE Symposium in Durban in 1999, and attended several INTIMATE Workshops. His death was a great loss to Quaternary science.

Fig 3. Sigfus, Barbara etc at HoorThe INTIMATE Steering Group, Hoor, Sweden, 1997. Left to right: Sigfus Johnsen, John Lowe, Barbara Wohlfarth, Karen-Luise Knudsen, Svante Bjorck and Mike Walker; inset, Les Cwynar.

Workshops and Symposia, 1995-2009

Following the inaugural meeting in Berlin, a series of Workshops and Symposia have been held during which the aims of the programme have been discussed and further developed. There have been nine International Workshops:

Hoor, Sweden, October, 1997, convened by Svante Bjorck, Karen-Luise Knudsen, Sigfus Johnsen and Barbara Wohlfarth. The theme of the meeting was the subdivision and chronology of the Last Termination in relation to the ice-core record, and the meeting was attended by 49 scientists from 13 countries.

Fredericton, Canada, August, 1998, convened by Les Cwynar and attended by more than 30 scientists. This meeting reviewed a range of data-sets from the last-interglacial transition from both western Europe and eastern North America.

Fig 4. Les Cwynar.KillarneyLes Cwynar with a core from Killarney Lake during the fieldtrip associated with the New Brunswick Workshop, 1998

Fig 5. Wim, Mike and JohnJohn Lowe, Mike Walker and Wim Hoek at the INQUA Congress in Durban, South Africa, 1999

Kangerlussuaq, Greenland, August, 2000, convened by Ole Bennike and Jorgen-Peder Steffensen and attended by 31 INTIMATE project members from 9 countries. The themes of the meeting were the standardisation of procedures for the calibration and publication of radiocarbon dates, and comparisons of datasets from the Last Termination on a common (calendar) timescale

Fig 6. Kanger00Participants in the Kangerlussuaq Workshop on the Greenland ice sheet

Tromso, Norway, June, 2002, convened by Nalan Koc, Morten Hald and Torre Vorren, and attended by 36 INTIMATE project members from 12 countries. Discussion at the workshop centred on improving the reliability of correlation between marine, terrestrial and ice-core sequences.

Fig 7. Tromso jpgPre-Workshop dinner drinks at the ‘Midnight Sun Workshop’, Tromso

Reno, Nevada, July, 2003, organised by Wim Hoek. The workshop, which was held at the XVth INQUA Congress, was attended by 33 scientists from 14 countries, considered the question of whether climatic oscillations during the Last Termination were globally synchronous.

Bonn, Germany, 2004, convened by Thomas Litt. The meeting reviewed new data from a range of proxy records, discussed recent developments in the chronology of the Last Termination, and considered proposals for future meetings and associated research agendas. The workshop was attended by 38 participants from 12 countries.

Fig 8. Bonn fieldtripHans-Ulrich Schmincke explains the stratigraphy at the type locality of the Laacher See Tephra (Wingertsberg)
on a field excursion during the Bonn Workshop

Myraldur, Iceland, September, 2005, organised by Jon Eiriksson, Arny Sveinbjornsdottir, Olafur Ingolfsson and Sigfus Johnsen. Discussion centred on new records from the North Atlantic region, on geochronology, and on correlation. The meeting was attended by 28 scientists from 8 countries.

Fig 9. Myraldur, IcelandParticipants in the Myraldur Workshop, Iceland, 2005

Cairns, Australia, August 2007, held at the XIVth INQUA Congress, convened by Wim Hoek, and attended by representatives from both Hemispheres.

Oxford, UK, September, 2008, organised by Simon Blockley, Chris Bronk Ramsey and Christine Lane, along with colleagues from the Research Laboratory for Archaeology and the History of Art in Oxford (Peter Ditchfield, Anna Oh and Richard Staff). The workshop reviewed recent developments in dating and high-precision correlation, and considered future directions for INTIMATE, including a proposed application to the EU COST Action Programme.

Fig 10. OxfordParticipants in the Oxford Workshop, 2008

In addition to the Workshops, INTIMATE-sponsored Symposia and Poster Sessions have been organised at the INQUA Congresses in Durban (1999), Reno (2003), and Cairns (2007), and at the annual European Geoscience Union (EGU) General Assembly in Vienna (2008).

Developments in the INTIMATE programme

Although the original aims of INTIMATE remain largely unchanged, there have been important developments within the programme. Following on from NASP, INTIMATE focussed initially on the North Atlantic realm but, after discussions at the Durban INQUA, it was agreed to expand the geographical coverage to include the South Atlantic and Mediterranean regions. At the Tromso Workshop, the decision was taken to expand the remit further and to adopt a global perspective. This opened the way to the establishment of the first Southern Hemisphere INTIMATE Group in Australasia (OZ INTIMATE) in 2004 (Turney et al., 2006a). Rewi Newnham was appointed overall Co-ordinator, with Jamie Shulmeister responsible for the New Zealand sub-group and Simon Haberle for the Australia sub-group. Since the establishment of OZ INTIMATE, six Workshops have been held (Sydney, 2004; Wellington, 2004, 2005; Auckland, 2006; Sydney 2009; and Stradbroke Island, Queensland, 2010).

In addition to expanding the geographical coverage of INTIMATE, the temporal range of the programme has also been increased. The initial focus of the programme was on the Last Termination (sensu lato), broadly between 18 and 8 ka BP. At the Tromso Workshop (2002), it was agreed that the remit of INTIMATE should be extended to cover the interval 30-8 ka BP and, at the Oxford Workshop (2008), the decision was taken to extend this even further, back to 60 ka BP to reflect the time period covered by the new high-resolution GICC05 chronology from the GRIP and NGRIP ice cores, and the extension of the range of radiocarbon calibration (INTCAL09).

Links with international research groups and organisations

INQUA (International Union for Quaternary Research): INTIMATE was formally accepted as a Working Group of the INQUA Palaeoclimate Commission in Durban (1999) and re-affirmed as such at the Reno Congress in 2003. As noted above, INTIMATE-sponsored symposia were held at these two meetings, and also at the INQUA Congress in Cairns (2007). INTIMATE received financial support from INQUA during the 1999-2003, and 2003-2007 inter-Congress periods. Following reorganisations within the structures of INQUA, in 2007 INTIMATE became an ‘International Focus Group’ of the Palaeoclimate Commission, with the North Atlantic and Australasian INTIMATE Groups designated as separate ‘Research Projects’. Both projects received further financial support from INQUA during the 2007-2011 inter-Congress period.

PAGES (Past Global Changes: IGBP): In 2001, formal links were established between INTIMATE and the PAGES PEP (Pole-Equator-Pole) Programme. INTIMATE was represented at the PAGES International Meetings in London (John Lowe) and Aix-en Provence (Wim Hoek), and Jef Vandenberghe and John Lowe were responsible for INTIMATE’s contribution (Vandenberghe et al., 2004) to the major PAGES synthetic volume dedicated to PEP III (the transect through Europe and Africa; Battarbee et al., 2004).

Subcommission on Quaternary Stratigraphy (SQS): At the 2004 Workshop in Bonn, it was agreed that INTIMATE should respond to an invitation from the SQS (a subcommission of the International Commission on Stratigraphy: ICS) to form a Joint Working Group to define the stratotype for the base of the Holocene in the Greenland NGRIP ice core. The Working Group involved 19 scientists from 10 countries under the chairmanship of Mike Walker, and the outcome of the Group’s deliberations are described below.

Principal achievements of INTIMATE 1995-2009

An event stratigraphy for the North Atlantic region: The formulation of an event stratigraphy for the North Atlantic region based on the oxygen isotope signal in the GRIP ice core was the principal outcome of discussions at the Hoor Workshop in 1997. This approach was initially suggested by the late Sir Nick Shackleton, who was a participant in the Hoor Workshop. The isotopic profile spanning the time interval 23-11 ka BP was divided into a series of stadials and interstadials and sub-stadials/sub-interstadials, which formed a stratigraphic template for the sequence of climatic changes that occurred during the Last Termination in Greenland and adjacent areas of the North Atlantic. Details can be found in Bjorck et al. (1998) and Walker et al. (1999). This scheme has since been widely adopted and the terminology is now routinely employed throughout the North Atlantic province.

fig 11. event stratigraphy
The INTIMATE event stratigraphy for the Last Termination (after Bjorck et al., 1998).

Protocols for ice-ocean-land correlation: These were first discussed at the Kangerlussuaq Workshop in 2000. They involved (a) recommendations for the use of 14C dates and for the derivation of reliable age estimates based on 14C (including issues of site selection; the provision of contextual information on 14C dates; the use of calibration programmes; wiggle matching to the 14C calibration curve; and the use of Bayesian and other statistical methods); (b) the use of an event-stratigraphic approach in inter-regional correlations; and (c) the employment of time-parallel markers horizons based on tephras, δ18O stratigraphy, and palaeomagnetic signals (Lowe et al., 2001). Further discussion of these issues at the Tromso, Bonn and Myrdalur Workshops resulted in a revision and updating of these protocols, along with an extension of the time range to 30 ka BP (Lowe et al., 2008). More recently, the INTIMATE event stratigraphy has been further extended to 48 ka BP (Blockley et al. 2011, Quaternary Science Reviews,in press.

Developments in geochronology: INTIMATE scientists have been involved in two important aspects of the geochronology of the Last Termination: (a) in refinements in 14C age modelling using Bayesian and other statistical approaches (e.g. Bronk Ramsey, 2008; 2009; Blockley et al., 2007, 2008); and (b) in the development of high-resolution ice core-chronologies, most notably the GICC05 timescale on the NGRIP core, which was first presented during the Carlsberg Dating Conferences (2005, 2006), Carlsberg Academy, Copenhagen (Rasmussen et al., 2006; Svensson et al., 2008).

fig 12. ice cores 830 ka
Comparison of the δ18O records for the NGRIP and GRIP ice-core records for the last 30,000 years at a 50-year resolution (after Lowe et al., 2008).

Developments in tephrochronology: Major advances have been made in tephrochronology in recent years. They include the recovery of non-visible tephras from marine and terrestrial sediments; refinements in the geochemical fingerprinting of tephras; the dating of tephra horizons; the detection of volcanic signals in ice cores, and the development of increasingly comprehensive tephra data-bases. In the North Atlantic region, for example, more than twenty tephra isochrones have been identified from the Last Termination alone. INTIMATE scientists have been at the forefront of many of these developments (Davies et al., 2002; Turney et al., 2004, 2006b; Davies et al, 2011).

Ratification of the Pleistocene-Holocene boundary: As described above, a Joint Working Group of INTIMATE and the Subcommission on Quaternary Stratigraphy (SQS) was established to bring forward a proposal for the definition of the Pleistocene-Holocene boundary (Global Stratotype Section and Point: GSSP) based on the NorthGRIP Greenland ice core. The boundary was identified using a range of physical and chemical properties, and a timescale, based on multi-parameter annual layer counting provides an age of 11,700 calendar yr b2k (before AD 2000) for the base of the Holocene, with a maximum counting error of 99 yr. Five auxiliary stratotypes (Splan Pond, eastern Canada; Cariaco Basin, Venezuela; Eifelmaar Lakes, Germany; Lake Suigetsu, Japan; and Lake Maratoto, New Zealand) were recommended to support the proposal. This was submitted to the International Commission on Stratigraphy (ICS) via the SQS and, in May 2008, the Executive Committee of the International Union of Geological Sciences (IUGS) ratified the Holocene GSSP located at 1492.45m depth in the NGRIP ice core, Greenland (Walker et al., 2008; 2009).

Fig 13. Holocene boundary

The visual stratigraphy of the NGRIP core between 1491.6 and 1493.25 m depth obtained using a digital line scanner. Here the image is ’reversed’ so that clear ice shows up black, whereas the cloudy bands, which contain relatively large quantities of impurities, in particular micrometre-sized dust particles from dry areas in eastern Asia, appear white. The location of the Pleistocene–Holocene boundary at 1492.45 m is shown in the enlarged lower image (after Walker et al., 2009).