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Victoria University Antarctic Research Expedition Science and Logistics Reports 2004-05: VUWAE 49

2 Proposed Programme

2 Proposed Programme

Seven key locations were identified for the NZ ITASE (International Transantarctic Scientific Expedition) programme. The analyses on the ice core from the first site, Victoria Lower Glacier in the McMurdo Dry Valleys, have almost been completed. For the 2004/05 field season we proposed to recover intermediate length cores from sites 2 and 3: Evans Piedmont Glacier and Mt Erebus Saddle. Additionally we recover a shallow 21m core from Windless Bight. Furthermore we continued our longer-term mass balance measurement time series at Victoria Lower Glacier.

Evans Piedmont Glacier Ice Core Record

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To our knowledge the Evans Piedmont Glacier site is, with 380m asl, the lowest elevation site identified for drilling in Antarctica. As such it has the potential to provide a climate record with unprecedented sensitivity for tropospheric climate variability and hereby contributing directly to the discussion on the dominant driving force of Antarctic climate variability [van den Broeke, 2000; Hall and Visbeck, 2002; Thompson and Solomon, 2002; Venegas, 2003].

The Evans Piedmont Glacier is located in the vicinity of the proposed ANDRILL site in 'Granite Harbour', which is expected to provide also a Holocene record. The comparison of the overlap between the two records provides us with the unusual opportunity to distinguish between the terrestrial and marine signal. This will add significantly to the discussion on the relative importance of the Antarctic Circumpolar Wave (ACW, oceanic), Southern Annular Mode (SAM, atmospheric), and El Niño Southern Oscillation (ENSO, both); their forcing and feedback mechanism. Furthermore, the sub-annual to decadal ice core record from Evans Piedmont Glacier can help to tune the marine Granite Harbour record and potentially provides a record of the final retreat of the Ross/McMurdo Ice Shelf.

The regional climate record contained in the ice will provide background information for the Latitudinal Gradient Project site 'Granite Harbour', especially for temperature, precipitation, sea-ice extent, storminess, seasonality, and snow accumulation. As mentioned before, this will help to determine if the current ecological system found has evolved under prevailing climate, or how much time the ecological system had to adjust to potential climate change in the recent past. In collaboration with the US ITASE effort (a traverse from South Pole to Northern Victoria Land along the plateau side of the Transantarctic Mountains) we aim to provide continentality and elevation gradients, to compliment to our understanding of deep ice core records from the Antarctic interior. Furthermore, the importance of katabatic winds and the intrusion frequency of marine airmasses into the Antarctic interior through time can be established.

Mt. Erebus Saddle Ice Core Record

Mt Erebus Saddle lies in the pathway of the ENSO initiated katabatic surges across the Ross Ice Shelf [Cullather et al., 1996; Bromwich et al., 2000] and also of enhanced cyclonic activity from the Southern Ocean [Bertler et al., 2004]. Therefore, the ice core record from Mt Erebus Saddle is likely to show the strongest ENSO influence of all proposed sites. The ENSO record (Southern Oscillation Index) is short and various proxies have been tentatively proposed to reconstruct ENSO variability [Adams et al., 2003; Tudhope and Collins, 2003]. The ice core record from Mt Erebus Saddle potentially provides a mean to reconstruct ENSO since its initiation in the early Holocene. Furthermore, the comparison between Mt Erebus and Mt Prior at Cape Hallett will provide a mean to distinguish ENSO driven climate variability from SAM and ACW forcing.

The semi-permanent Ross Ice Shelf polyna, just east of Ross Island, is also the result of these katabatic winds and is an important area for the production of sea-ice [King and Turner, 1997] and Antarctic Bottom Water [Bromwich et al., 1993]. The Mt Erebus ice core is likely to provide a record of the winter polyna activity through time, via the marine fingerprint in the ice chemistry. Moreover, the Mt Erebus Saddle is located in the vicinity of the proposed ANDRILL location 'Windless Bight'. The sub-annual to decadal ice core record provides a high resolution Holocene record for the much longer but overlaying ANDRILL ice shelf and marine record.

Additionally, the site is only 37km from Scott Base and McMurdo Station and will provide a long-term perspective on climate variability and iceberg discharge, relevant for both, Evans Piedmont Glacier and Mt Erebus sites.