In order to model predictions of environmental and climatic response to anthropogenic forcing it is essential that we can identify the magnitude and timing of historical natural climatic variations (e.g. the Little Ice Age and the Medieval Warm Period), and interpret their influence on the ecosystem (Terray & Cassou 2000; Broecker 2000). Pre-instrumental records of such episodes necessitate the use of proxy-indicators as recorders of past changes in terrestrial and marine environmental conditions. These geochemical and biological palaeo proxies may be used to reconstruct such variations as fresh water inputs, sea surface temperature (SST), salinity and the redox conditions of sediments and bottom waters (Crusius and Thomson 2000; Brown et al 2000; Nurnberg et al 2000; Shimmield et al 1995).  High temporal resolution records derived from proxy-indicators are found in ice cores (Dansgaard et al 1993) and corals (Beck et al 1997; Smith et al 1997a; Tudhope et al 2001; Tudhope et al 1995). In contrast, the oceanic palaeo-record has a much lower temporal resolution (Kroon et al 2000, Martinez et al 1999; 2000; Shimmield et al 1990a). However, fjords or sealochs, spanning much of the land-sea interface of north-western Europe, contain rapidly accumulating sediments that archive both broad scale, long-term (thousands of years) and short term (annual to decadal) records (Shimmield et al 1995b) that are lacking in offshore sediments.  Syvitski et al. (1987) estimate that nearly a quarter of all terrestrial sediment transported to the oceans during the last 100ka now resides in fjordic basins.  Such sediments offer the potential to provide the annual to decadal resolution and environmental sensitivity necessary to reveal the extent and effects of environmental fluctuations with time in northern coastal seas.

Improved reconstruction of past environmental change involves temporal linking of the marine  e.g. Austin and Scourse (1997) and  terrestrial e.g. Briffa et al. (2001) records usually achieved by using ¹⁴C dating.  The “reservoir effect” of ¹⁴C for the deep ocean is about 400 years and commonly this is applied to the coastal environment.  Due to the large catchment areas and resulting high freshwater input fjord environments, it is conceivable that this figure is incorrect. An evaluation of the ¹⁴C reservoir effect may be made by analysing both marine and terrestrial-derived organic material from identified horizons in the sedimentary record, which will be linked using independent, chronological markers such as tephra layers.

The palaeo-proxies used to assess environmental and climatic change, such as dO¹⁸and dC¹³ in foraminifera and mollusc shells and geochemical indicators (e.g. Ba, Mn, Fe U, Re, and Mo) will be analysed at high spatial resolution in a selected number of cores taken over a northern latitudinal gradient.  The results obtained for recent sediments will be compared with instrumental records allowing a high degree of calibration and validation of individual proxy indicators. Recent accumulation and mixing rates over the last 150 years will be quantified using natural (²¹⁰Pb, ²³⁴Th) and anthropogenic radionuclides (¹³⁷Cs, ^239,240Pu) and stable Pb isotopes (²⁰⁶Pb/²⁰⁷Pb) (Shimmield et al 1995).  Evaluated proxies within foraminifera (Austin & Evans 2000; Austin & Scourse 1997), along with such indicators as  U₃₇^K' within the preserved organic fraction, will also be measured and used to reconstruct SST and salinities (Zhao et al 2000). Down core profiles of redox sensitive indicators such as Mn, Fe, Mo, U, and particularly Re, from these rapidly accumulating sediments will supply high-resolution records of past bottom water oxygenation.  Variation in fresh water inputs and water column conditions over pre-industrial history will be modelled using such data.  A comparison of reconstructed palaeo SSTs from alkenones, oxygen isotopes and foraminiferal transfer functions from the same locations will be made and an assessment of any inconsistencies and conformities between the methods carried out.  Cross-comparison of proxy indicators from several latitudinal sites using combined geochemical, palaeontological and sedimentological techniques offers the potential for the unique identification of local versus regional effects in coastal high latitude climatic evolution, and will make a significant contribution to the new NERC thematic programme on Abrupt Climate Change

Objectives:

1. To identify and calibrate suitable palaeo-proxies from new high-resolution cores obtained from fjordic (sea loch) environments.

2. To reconstruct past sea surface temperature, salinities and turnover events (palaeo redox conditions) within fjordic environments and compare SSTs obtained from alkenones, dO¹⁸ and foraminiferal transfer functions from the same material.

3. To quantify the ¹⁴C reservoir effect within fjordic environments with respect to high and varying fresh water inputs.

4. To deliver an understanding of the effect of abrupt climate change and land use on fjordic/sea loch systems, which link the marine and terrestrial environments at high latitudes in Northwest Europe.