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.
It is widely accepted that the Earth's climate is warming and that glaciers are losing mass and increasing sea level. Small glaciers are particularly susceptible but only represent a fraction of the Earth's freshwater stored as ice. In contrast, the huge ice sheets in Greenland and Antarctica store several 10s of metres of equivalent sea level and recent studies suggest that they, too, are losing mass and that this appears to be accelerating. Ice sheets transfer ice to the oceans via numerous fast flowing glaciers called 'ice streams'. It has been discovered that ice streams can speed up, slow down, and even stop altogether; as well as switch their position. These changes can occur relatively rapidly (over a few years) but it is not clear whether they are part of a long-term trend of ice sheet shrinkage (over centuries to millennia) or simply reflect their natural variability. Another possibility is that the recent acceleration and thinning is the beginning or 'pre-cursor' of an episode of widespread mass loss but the question remains: how important are ice streams in accelerating ice sheet deglaciation, e.g. beyond that which might be excepted from climate forcing alone? In order to assess the significance of these short-term changes, we need to understand how ice streams operate over time-scales longer than current measurements allow and we also need to view ice streams as an integrated pattern of drainage within the ice sheet that evolves over several millennia. This can be achieved through investigation of past ice stream behaviour. Past-ice streams can be identified because, compared to slow-flowing ice, their rapid flow creates distinctive glacial landforms on the now-exposed ice sheet bed. We can locate these ice stream 'footprints' on past ice sheet beds very easily (e.g. in the UK or North America) and then use dating techniques (e.g. radiocarbon dating) and other evidence related to ice sheet flow patterns to estimate when and for how long they existed. This approach has been taken by scientists and has increased our understanding of their behaviour over long time-scales but studies have tended to focus on just one ice stream or specific regions. What we really want is information on the activity of lots of ice streams from across an entire ice sheet and, ideally, from as long a time-span as possible i.e. from a complete deglaciation, when the ice sheet shrinks from its maximum extent and disappears altogether. This aim of this project, therefore, is to produce a ground-breaking dataset that reconstructs the spatial and temporal activity of every ice stream in the North American Laurentide Ice Sheet (which was similar in size to Antarctica) from its maximum extent around 21,000 yrs ago to its near-disappearance around 5,000 yrs ago. We will map all the flow patterns on the ice sheet bed, including ice streams, and date these using an existing database of ~4,000 radiocarbon dates (and other published dates). A recent pilot study shows that we can date the duration of individual ice streams to within 250-500 yrs. This will allow us to see how an entire drainage network of ice streams evolves during deglaciation and whether their combined activity caused major episodes of significant mass loss. It will also reveal the extent to which ice stream activity is linked to abrupt climate and sea level changes in the past, e.g. abrupt warming or cooling and rapid changes in sea level. Taken together, this will provide a firm context with which to model and predict the future response and likely magnitude of changes in modern-day ice sheets, e.g. for the next IPCC Report.
Recent work has shown that the single largest unknown in assessing the contribution of mountain glaciers and ice caps to contemporary global sea-level rise is the rate of mass loss by iceberg calving from large Arctic ice caps (Radic and Hock, 2011, Nature Geoscience). The largest ice caps in the Arctic, and indeed the largest ice masses outside the Antarctic and Greenland ice sheets, are those of the Canadian Arctic islands. Importantly, new findings indicate that, for 2004-2009, a sharp increase in the rate of mass loss also makes the Canadian Arctic Archipelago the single largest contributor to global sea-level rise outside Greenland and Antarctica (Gardner et al., 2011, Nature). Each of these large Canadian ice caps is divided into a series of drainage basins that flow into fjords via narrow, heavily crevassed fast-flowing outlet glaciers which dissect the islands' fringing mountains. A major question for scientists and policymakers is, therefore, how these ice caps will continue to react to the temperature rises that are predicted for the 21st century, noting that Atmospheric General Circulation Models predict that temperature rise will be significantly greater in the Arctic than at lower latitudes. Numerical modelling of large ice masses is constrained, however, by a lack of knowledge of the geometry and nature of the bed of these outlet glaciers. We will acquire geophysical data from ice-cap outlet glaciers draining the large ice caps on Ellesmere and Devon islands in the Canadian Arctic using an airborne ice-penetrating radar, laser altimeter, gravimeter, magnetometer and GPS instruments. We will focus on three key areas of each drainage basin: the heavily crevassed fast-flowing outlet glaciers themselves, an upper transition zone between the ice-cap interior and the narrow outlet glaciers; and the grounding zone marking the transition to floating ice tongues at the head of some Canadian High-Arctic fjords. Our scientific objectives are: (a) to determine ice-surface and subglacial-bed elevation; (b) to characterize the substrate, in particular whether it is bedrock or deformable sediment; (c) to establish the distribution of subglacial melting; (d) to reveal basal character changes at the transition zones between inland ice, outlet glaciers and the grounding zone; (e) to provide new estimates of outlet glacier calving fluxes and their variability on up to decadal timescales. This information, integrated with satellite datasets on outlet-glacier surface motion and our earlier observations of the regional-scale geometry of these ice caps, will provide fundamental boundary conditions for the numerical modelling of these ice caps and, thus, how they may respond to atmospheric and ocean warming over the coming decades, with implications for sea-level rise.
As anthropogenic atmospheric warming is forecasted to exceed 2C above preindustrial temperatures by 2100, a key uncertainty in predicting the impact of this change is the quantitative understanding of how this warming will be distributed in the oceans and atmosphere. One means of assessing this is to look to the geological past, especially the late Cretaceous to Eocene (100-34 Ma ago), when atmospheric pCO2 levels were last as high as the 700 ppmv forecasted for 2100, and global mean annual temperatures (MAT) were up to 8C warmer than today (the so-called "Greenhouse World"). Fossil data suggest that temperature-sensitive organisms, such as reptilians, were living in the Arctic-circle during this period, and led to the emergence of the "Equable Earth" hypothesis - a scenario that invokes near total collapse of the meridional, equator-to-pole temperature gradient at this time. This indicates a climate system that operated in a fundamentally different way to the modern "Icehouse World", with a different/enhanced means of transporting heat from the tropics to the poles. A fundamental problem for scientists aiming to predict future climate change, is that state-of-the-art models are not able to reproduce the degree of collapse of the global meridional temperature gradient suggested by fossil data, reflecting a problem with either the "Equable Earth" hypothesis, or with climate modelling. Either way, this uncertainty impedes our ability to confidently predict the impact of future climate change with far-reaching implications. This research will be the first robust test of the "Equable Earth" hypothesis. We will reconstruct meridional variation in land surface MAT in a transect along the North American Continent, spanning mid- to high-palaeolatitude for several discrete time-equivalent instantaneous time-slices spanning the Cretaceous-Palaeogene (K-Pg) boundary - an interval in the middle of the "Greenhouse World". The MATs will be reconstructed using the brGDGT palaeotemperature proxy from collected coal samples. brGDGTs are lipids produced by bacteria thriving in terrestrial environments, whose distribution is a function of land surface MAT and can be used to reconstruct land surface MATs. We have identified ten separate sites, spanning 47-75N of palaeolatitude, where coals (fossil peats) were demonstrably accumulating coevally, by the occurrence within each of the coals of the globally synchronous Iridium (Ir)-enriched layer that settled from the atmosphere after the impact of a meteorite at the K-Pg boundary. In addition to the Ir-enriched layer, the coals contain datable tephra horizons, which will constrain vertical rates of change of MAT from time-slice to time-slice. They also contain distinctive carbon isotopic events before, during and after the Ir- enriched layer, which provide additional correlatable time lines between all locations. Combined, this provides an unique opportunity to generate serial time-slice reconstructions of meridional land surface MAT gradients, spaced at sub-orbital durations, at this critical period in Earth history. This will provide us with the opportunity to critically test the "Equable Earth" hypothesis, by placing numerical bounds on meridional MAT gradients for a series of time slices in continental interiors at this time. By generating meridional MAT gradients for multiple intervals, and by generating a tephrochronologically-based time-series through the succession, it will be possible to place bounds on the rates of change of MAT in time, from mid- to high- latitude. This will also reveal, for the first time, the dynamics in space and time of the "Greenhouse Earth" climate system, and will also allow us to assess MAT in the aftermath of meteorite impact at the K-Pg boundary, giving insight into the response of the climate system to catastrophic change, and allowing us to test competing hypotheses of climate change as the driver for the mass extinction at the K-Pg boundary.
Previous work suggests that marine fjords are responsible for burying globally significant amounts of organic carbon (OC). Understanding the burial of terrestrial OC in fjords is important on a global scale, as previous work estimated that just the fine-grained fjord sediments are responsible for burying ~11% of global organic carbon flux into the oceans. More recently it was shown that coarse-grained sediment deposited by small rivers floods will significantly increase that amount of OC burial in fjords. Exceptionally large and infrequent floods, like glacial lake outburst floods (GLOFs), are likely to transport and bury larger amounts OC into coarse-grained fjord deposits, however their role remains poorly constrained due to their infrequent nature. Yet, constraining the full OC burial budget in marine sediments is important as these sediments are the second largest sink of atmospheric CO2 and thus contributes to long-term regulation of climate. An exceptional GLOF occurred on 28th Nov 2020 at Elliot Creek (BC, Canada) that now provides us a unique opportunity to study the OC burial efficiency of such extreme events. Reconstruction from the measured 4.9 Mw seismic activity that coincided with the event indicates the original landslide dislodged 30 million tonnes of sediment and triggered a ~100m high displacement-wave in the glacial lake. This wave in turn broke through the lake's moraine-dam, releasing large amounts of water, which powerfully scoured Elliott Creek before entering into the fjord. The event posed a hazard to marine traffic and coastal structures and destroyed significant salmon, wildlife and forest resources of Homalco First Nations. The Elliot Creek event moved large volumes of sediment and OC, which are ultimately deposited in the fjord. Fortuitously, Bute Inlet was previously the site of an extremely detailed time series of seabed surveys, as it was mapped ten times in between 2008 up to 2020. Recent work by our group at Bute Inlet has shown how turbidity currents transport young terrestrial OC from the river mouth down to the deeper fjord waters. The extensive background data on the bathymetry, the current dynamics and the geochemical signatures of the OC in the fjord under normal conditions now enable a unique opportunity to study the OC burial of large GLOFs. This proposal aims to test two hypotheses, which are: 1) large GLOFs can transport vast amounts of sediment and OC to the distal lobe and (2) young terrestrial organic matter can be efficiently buried in these deep water fjord sediment. Here, efficiency refers to direct transport from source to sink, as opposed the normal conditions in which OC only reaches this sink through many staggered smaller transport events. The opportunity is unique due to the combination of an exceptional flood and world-leading baseline data of Bute Inlet, having been repeatedly mapped, monitored and sampled over the last decade. Additionally, this opportunity is time limited, as normal turbidity currents activity returns this spring as the snow start to melt. These activities will start to rework, blur and bury the signature of this GLOF. The hypotheses will be tested by mapping the GLOF-related deposits throughout the fjord and characterising their OC components. Field data collection will be a combination of new bathymetric survey and sediment sampling, which can be compared to pre-event surveys and cores. Sediment and organic carbon characterisation will include grain-size analysis, XRD, total organic carbon, C-N-S, stable carbon isotope and radiocarbon composition as well as ramped pyrolysis-oxidation analysis. Combination of all routine organic geochemistry (TOC, CNS, d13C and 14C) and textural data will be used for initial fingerprinting of OC (marine or terrestrial source). Further separation of OC by RPO coupled with d13C and 14C measurements will detail the OC source, as previously demonstrated by our group.