Overview of the Lost Meteorites of Antarctica field campaigns

The Lost Meteorites of Antarctica project was the first UK-led Antarctic meteorite recovery expedition. The project has successfully confirmed two new high-density meteorite stranding zones in the Hutchison Icefield and Outer Recovery Icefields areas and investigated the geology of three previously unvisited Antarctic nunataks (Turner Nunatak, Pillinger Nunatak, Halliday Nunatak). The project undertook meteorite searching on the ice surface via skidoo reconnaissance and systematic searching and developed a novel pulse induction metal detection system to search for englacial iron-rich meteorites trapped within the upper one meter of ice. In total, 121 meteorites have been recovered from the ice surface searching activities, which are now curated in the United Kingdom at the Natural History Museum London and are available for scientific analysis

Rothlisberger channels with finite ice depth and open channel flow

AbstractThe theoretical basis of subglacial channel dynamics can be traced back to the work of Röthlisberger (1972) and Nye (1953). Röthlisberger (1972) considered the channels’ behaviour to be governed by a mix between water friction melting back the channel walls and the viscous closure of the surrounding ice; Nye (1953) derived a viscous closure rate for the ice. While their modelling is evidently well constructed, two aspects of their work have gone undeveloped. The first is the consideration of a finite glacier depth within the viscous closure law, instead of the assumption of an infinite glacier depth. The second is the allowance of a region of open channel flow, so that a channel’s water may transition from a region of closed channel flow to one where the water is exposed to the atmosphere. This paper helps close these two gaps, showing how Nye’s equation for the rate of ice closure can be modified, and how the point of transition between closed and open channel flow may be determined.</jats:p

Mineral Reserves under Price Uncertainty

National reporting organizations and regulatory bodies for the minerals and mining sector are requiring publicly reported Ore- Reserve estimates to take account of uncertainties. Whilst methodologies that account for physical uncertainty appear relatively well developed, methodologies which can take account of economic uncertainty appear much less so. To counter this shortfall, we present an efficient and general methodology which can quantify the effect of price uncertainty within reserve estimates, providing both the expected reserve size and the associated distribution (box whisker plot). This statistical information can be used by interested parties to understand precisely where the reserve risks lie, which we highlight in a worked example

Mine Valuation in the Presence of a Stochastic Ore-Grade Uncertainty

Mining companies world-wide are faced with the problem of how to accurately value and plan extraction projects subject to uncertainty in both future price and ore grade. Whilst the methodology of modelling price uncertainty is reasonably well understood, modelling ore-grade uncertainty is a much harder problem to formulate, and when attempts have been made the solutions take unfeasibly long times to compute. By treating the grade uncertainty as a stochastic variable in the amount extracted from the resource, this paper provides a new approach to the problem. We show that this method is well-posed, since it can realistically re flect the geology of the situation, and in addition it enables solutions to be derived in the order of a few seconds. A comparison is made between a real mine valuation where the prior estimate of ore grade variation is taken as fact, and our approach, where we treat it as an uncertain estimate

Regulating Industries under Exogenous Uncertainty

We present a quantitative method to find jointly optimal strategies for an industry regulator and a firm, who operate under exogenous uncertainty. The firm controls its operating policy in order to maximize its expected future profits, whilst taking account of regulatory fines. The regulator aims to control the probability that the firm enters a given undesirable state, such as ceasing production, by imposing a fine which is as low as possible, while achieving the required reduction in probability. The exogenous uncertainty is modeled using a stochastic differential equation, and we show this implies that the firm's behavior can be solved via the Hamilton-Jacobi-Bellman equation, and the regulatory fine can be obtained via the Feynman-Kac formula. We discuss both analytic and numerical solution methods. Our results are illustrated for a security of supply problem for vaccine production where future production costs are uncertain and, using empirical data, for an abandonment problem in a gold mining operation where future commodity prices are uncertain. The method determines the level of fine which establishes a Nash equilibrium in these nonzero-sum games, under uncertainty

The Determination of a Dynamic Cut-Off Grade for the Mining Industry

Prior to extraction from a mine, a pit is usually divided up into 3-D `blocks' which contain varying levels of estimated ore-grades. From these, the order (or `pathway') of extraction is decided, and this order of extraction can remain unchanged for several years. However, because commodity prices are uncertain, once each block is extracted from the mine, the company must decide in real-time whether the ore grade is high enough to warrant processing the block further in readiness for sale, or simply to waste the block. This paper first shows how the optimal cut-off ore grade—the level below which a block should be wasted—is not simply a function of the current commodity price and the ore grade, but also a function of the ore-grades of subsequent blocks, the costs of processing, and the bounds on the rates of processing and extraction. Secondly, the paper applies a stochastic price uncertainty, and shows how to derive an efficient mathematical algorithm to calculate and operate a dynamic optimal cut-off grade criterion throughout the extraction process, allowing the mine operator to respond to future market movements. The model is applied to a real mine composed of some 60,000 blocks, and shows that an extra 10% of value can be created by implementing such an optimal regime

A Freshwater Starvation Mechanism for Dansgaard-Oeschger Cycles

Ice core records indicate that the northern hemisphere underwent a series of cyclic climate changes during the last glacial period known as Dansgaard-Oeschger cycles. The most distinctive feature of these is a rapid warming event, often attributed to a sudden change in the strength of the Atlantic meridional overturning circulation (AMOC). We suggest that such a change may have occurred as part of a natural oscillation, which resulted from salinity changes driven by the temperature-controlled runoff from ice sheets. Contrary to many previous studies, this mechanism does not require large freshwater pulses to the North Atlantic. Instead, steady changes in ice-sheet runoff, driven by the AMOC, lead to a naturally arising oscillator, in which the rapid warmings come about because the Arctic Ocean is starved of freshwater. The changing size of the ice sheets, as well as changes in the background climate, would have aected the magnitude and extent of runoff, which altered the period and magnitude of individual cycles. We suggest that this may provide a simple explanation for the absence of the events during interglacials and around the time of glacial maxima