• Canada
• 2012-2021close
• 2010 close
• 2013 close

Modern marine ecosystems were established during the early Palaeozoic radiations of animals, first the 'Cambrian Explosion' and then, some 50 million years later, in the 'Great Ordovician Biodiversification Event.' By tracking the details of diversification through this critical interval, it should be possible to reconstruct not only the dynamics early animal evolution, but also the underlying effects of accruing ecological novelty. Unfortunately, the conventional fossil record represents only a fraction of ancient diversity, while famous 'soft-bodied' biotas such as the Burgess Shale are too rare to provide larger-scale patterns. I propose to circumvent these problems by exploiting a new, largely untapped source of palaeontological data: Burgess Shale-type microfossils. Like their macroscopic counterparts these fossils record the presence of non-biomineralizing organisms, but they also extend the view to include previously unrecorded forms and fine features. More significantly, they are proving to be quite common - to the extent that they can begin to be used to test macroevolutionary hypotheses. Systematic analysis of Burgess Shale-type microfossils through the Middle to Late Cambrian will shed fundamental new light on early evolutionary patterns, not least the poorly known interval between the Cambrian and Ordovician radiations. By integrating this enhanced fossil record with the principles of biological oceanography and macroecology, this study will also provide a unique, evolutionary view of how modern marine ecosystems function. This study will focus on the Western Canada Sedimentary Basin, which contains one of the largest, best preserved and most extensively sampled sequences of early Palaeozoic rocks on Earth. In addition to famously fossiliferous units exposed in the Rocky Mountain Fold and Thrust Belt - including the Burgess Shale itself - strata extend eastwards for over 1000 km in the subsurface, where they have been penetrated by hundreds of petroleum exploration boreholes. These subsurface materials are housed in state-of-the-art storage facilities in Calgary, Alberta and Regina, Saskatchewan and offer a unique opportunity to sample systematically through the whole of the Middle-Late Cambrian, and across an expansive shallow-water platform into continental-margin environments exposed in the Rocky Mountains. Preliminary work in both subsurface and outcrop occurrences has identified an exquisite range of Burgess Shale-type microfossils. More comprehensive sampling and analysis will substantially advance our understanding of early Palaeozoic diversity, macroevolutionary patterns, and the co-evolution of ecosystem function and environments.

Palaeoclimate reconstructions extend our knowledge of how climate varied in times before expansive networks of measuring instruments became available. These reconstructions are founded on an understanding of theoretical and statistically-derived associations acquired by comparing the parallel behaviour of palaeoclimate proxies and measurements of varying climate. Inferences about variations in past climate, based on this understanding, necessarily assume that the associations we observe now hold true throughout the period for which reconstructions are made. This is the essence of the uniformitarian principle. In some northern areas of the world, recent observations of tree growth and measured temperature trends appear to have diverged in recent decades, the so called 'divergence' phenomenon. There has been much speculation, and numerous theories proposed, to explain why the previous temperature sensitivity of tree growth in these areas is apparently breaking down. The existence of divergence casts doubt on the uniformitarian assumption that underpins a number of important tree-ring based (dendroclimatic) reconstructions. It suggests that the degree of warmth in certain periods in the past, particularly in medieval times, may be underestimated or at least subject to greater uncertainty than is currently accepted. The lack of a clear overview of this phenomenon and the lack of a generally accepted cause had led some to challenge the current scientific consensus, represented in the 2007 report of the IPCC on the likely unprecedented nature of late 20th century average hemispheric warmth when viewed in the context of proxy evidence (mostly from trees) for the last 1300 years. This project will seek to systematically reassess and quantify the evidence for divergence in many tree-ring data sets around the Northern Hemisphere. It will establish a much clearer understanding of the nature of the divergence phenomenon, characterising the spatial patterns and temporal evolution. Based on recent published and unpublished work by the proposers, it has become apparent that foremost amongst the possible explanations is the need to account for systematic bias potentially inherent in the methods used to build many tree-ring chronologies including many that are believed to exhibit this phenomenon. This proposal is designed to build on recent innovations in tree-ring chronology production techniques, also developed by the proposers. These new methods will produce tree-ring chronologies whose variability is unbiased, either by temporal changes in the age structure of the constituent sample series, or by any distortion in the data that can arise when using the previously applied techniques. The extensive reprocessed and improved data sets will then form the basis for many detailed, site-by-site comparisons of local climate and various tree-growth parameters in order to re-characterise the nature, strength and temporal stability of the climate/growth associations. This will represent a systematic and objective re-assessment of the evidence for divergence in different forest contexts. The project will then explore all of the current theories for the cause(s) of divergence employing both statistical and process-modelling techniques. The project will go on to use the reprocessed tree-ring data sets to re-calibrate many important climate reconstructions, with varying levels of spatial detail, and carefully assess the implications of the divergence effect, as newly characterised, on reconstruction uncertainty. This project will provide results that will inform the international scientific debate and widespread public perception of the reliability of tree-ring-based climate reconstructions in particular, but also our current understanding of the reliability of current evidence for high-resolution temperature changes during the late Holocene.

Antarctic sea ice thickness is arguably the largest gap in our knowledge of the climate system. While rapid changes in ice extent are evident in satellite imagery collected over the last three decades, we have little information with which to assess the thickness of the ice. Knowledge of the thickness distribution of sea ice and its snow cover is critical in understanding a wide range of air-sea-ice interactions. It's evolution over time provides a sensitive measure of the response of the polar regions to climate change and variability, and it controls the fluxes of heat, salt, and freshwater that govern air-sea interactions and water mass transformation. Whilst we are moving closer to the 'holy grail' of measuring Arctic sea ice thickness from space, such methods are severely limited in the Antarctic due to the deep snow cover. Moreover, our understanding of the processes that control Antarctic snow and ice thickness is inadequate. This proposal has two complementary lines of investigation: (1) To determine robust statistical relationships between snow depth, ice thickness, and freeboard distribution for a range of ice classes. Understanding these relationships is critical if we are to be able to determine either snow depth or ice thickness from space - the only viable means of determining large-scale snow and sea ice thickness, trends, and variability. (2) To quantify the role that key Antarctic sea ice processes play in controlling the ice thickness evolution and its response to climate forcing. This can only be achieved through detailed simultaneous measurements of both the surface topography and ice underside. We will obtain, for the first time anywhere, coincident 3D topography maps of both the surface (from airborne Lidar) and underside (from AUV mounted multibeam sonar) for a variety of ice types and conditions. With over 1 million individual measurements per sampling station, the richness of the data set will be several orders of magnitude more than is possible with traditional methods. This will allow us to determine, for the first time, robust statistical relationships between snow depth and ice thickness spatial variability. These data will allow a definitive assessment of the feasibility and accuracy of satellite methods for estimating Antarctic sea ice thickness and snow depth for a range of ice conditions. In addition we will deploy an unprecedented number (20) of novel ice mass balance buoys (IMBs) to monitor the evolution of the snow and sea ice throughout the annual sea ice cycle. The large number of IMB deployments will allow the first regional assessment of snow accumulation rates and ice mass balance of Antarctic sea ice. To achieve these goals we have secured a 30-day dedicated cruise aboard the James Clark Ross, scheduled for November 2010, as well as use of a BAS Twin Otter for airborne Lidar missions over ice stations and the surrounding region. These platforms, provided as part of the BAS core programme, along with support and instrumentation provided by project partners at no cost, represent a unique opportunity, and a significant leverage of over £1,000,000 of in-kind contribution. This is an unprecedented opportunity for the UK to lead a coordinated campaign to produce a definitive picture of snow and sea ice thickness distribution, and to continuously monitor the processes that control these distributions throughout the annual cycle. Our programme will deliver a major step forward in our knowledge of the snow and ice thickness distribution. It will advance our understanding of Antarctic sea ice processes and improve our ability to monitor the evolution of the ice cover and air-ice-ocean interactions on a large scale. This will allow improved representation of sea ice in large-scale and global climate models, and ultimately improve our understanding of the response of the Antarctic ice cover to current and future climate change and variability.