ADMAP-2: The next-generation Antarctic magnetic anomaly map

The Antarctic Digital Magnetic Anomaly Project compiled the first international magnetic anomaly map of the Antarctic region south of 60\ubaS (ADMAP-1) some six years after its 1995 launch (Golynsky et al., 2001; Golynsky et al., 2007; von Frese et al., 2007). This magnetic anomaly compilation provided new insights into the structure and evolution of Antarctica, including its Proterozoic-Archaean cratons, Proterozoic-Palaeozoic orogens, Palaeozoic-Cenozoic magmatic arc systems, continental rift systems and rifted margins, large igneous provinces and the surrounding oceanic gateways. The international working group produced the ADMAP-1 database from more than 1.5 million line-kilometres of terrestrial, airborne, marine and satellite magnetic observations collected during the IGY 1957-58 through 1999. Since the publication of the first magnetic anomaly map, the international geomagnetic community has acquired more than 1.9 million line-km of new airborne and marine data. This implies that the amount of magnetic anomaly data over the Antarctic continent has more than doubled. These new data provide important constraints on the geology of the enigmatic Gamburtsev Subglacial Mountains and Prince Charles Mountains, Wilkes Land, Dronning Maud Land, and other largely unexplored Antarctic areas (Ferraccioli et al., 2011, Aitken et al., 2014 \u327 Mieth & Jokat, 2014, Golynsky et al., 2013). The processing of the recently acquired data involved quality assessments by careful statistical analysis of the crossover errors. All magnetic data used in the ADMAP-2 compilation were delivered as profiles, although several of them were in raw form. Some datasets were decimated or upward continued to altitudes of 4 km or higher with the higher frequency geological signals smoothed out. The line data used for the ADMAP-1 compilation were reprocessed for obvious errors and residual corrugations. The new near-surface magnetic data were corrected for the international geomagnetic reference field and diurnal effects, edited for high-frequency errors, and levelled to minimize line-correlated noise. The magnetic anomaly data collected mainly in the 21-st century clearly cannot be simply stitched together with the previous surveys. Thus, mutual levelling adjustments were required to accommodate overlaps in these surveys. The final compilation merged all the available aeromagnetic and marine grids to create the new composite grid of the Antarctic with minimal mismatch along the boundaries between the datasets. Regional coverage gaps in the composite grid will be filled with anomaly estimates constrained by both the near-surface data and satellite magnetic observations taken mainly from the CHAMP and Swarm missions. Magnetic data compilations are providing tantalizing new views into regional-scale subglacial geology and crustal architecture in interior of East and West Antarctica. The ADMAP-2 map provides a new geophysical foundation to better understand the geological structure and tectonic history of Antarctica and surrounding marine areas. In particular, it will provide improved constraints on the lithospheric transition of Antarctica to its oceanic basins, and thus enable improved interpretation of the geodynamic evolution of the Antarctic lithosphere that was a key component in the assembly and break-up of the Rodinia and Gondwana supercontinents. This work was supported by the Korea Polar Research Institute

Basal conditions for Pine Island and Thwaites Glaciers, West Antarctica, determined using satellite and airborne data

We use models constrained by remotely sensed data from Pine Island and Thwaites Glaciers, West Antarctica, to infer basal properties that are difficult to observe directly. The results indicate strong basal melting in areas upstream of the grounding lines of both glaciers, where the ice flow is fast and the basal shear stress is large. Farther inland, we find that both glaciers have 'mixed' bed conditions, with extensive areas of both bedrock and weak till. In particular, there are weak areas along much of Pine Island Glacier's main trunk that could prove unstable if it retreats past the band of strong bed just above its current grounding line. in agreement with earlier studies, our forward ice-stream model shows a strong sensitivity to small perturbations in the grounding line position. These results also reveal a large sensitivity to the assumed bed (sliding or deforming) model, with non-linear sliding laws producing substantially greater dynamic response than earlier simulations that assume a linear-viscous till rheology. Finally, comparison indicates that our results using a plastic bed are compatible with the limited observational constraints and theoretical work that suggests an upper bound exists on maximum basal shear stress

Analysing aeromagnetic, airborne gravity and radar data to unveil variable basal boundary conditions for the East Antarctic Ice Sheet in the Wilkes Subglacial Basin

The Wilkes Subglacial Basin (WSB) extends for ca 1,400 km from George V Land into the interior of East Antarc- tica and hosts several major glaciers that drain a large sector of the East Antarctic Ice Sheet (EAIS). The region is of major significance for assessing the long-term stability of the EAIS, as it lies well below sea level and its bedrock deepens inland. This makes it potentially more prone to marine ice sheet instability, much like areas of the West Antarctic Ice Sheet (WAIS) that are presently experiencing significant mass loss. This sector of the EAIS has also become a focus of current research within IODP Leg 318 that aims to better comprehend the initial stages of glaciation and the history and stability of the EAIS since the Eocene-Oligocene boundary. Understanding geologi- cal boundary conditions onshore is important to assess their influence on ice sheet dynamics and long-term stability and interpret the paleo-ice sheet record. Early geophysical models inferred the existence of a major extensional sedimentary basin beneath the WSB. This could in principle be similar to some areas of the WAIS, where subglacial sediments deposited within rift basins or forming thin marine sedimentary drapes have been inferred to exert a key influence on both the onset and maintenance of fast-glacial flow. However, later geophysical models indicated that the WSB contains little or no sediment, is not rift-related, and formed in response to Cenozoic flexural uplift of the Transantarctic Mountains (TAM). A major joint Italian-UK aerogeophysical exploration campaign over parts of the WSB is super-seeding all these earlier geophysical views of the basin (Ferraccioli et al., 2009, Tectonophysics). Precambrian and Paleozoic basement faults can now be recognised as exerting fundamental controls on the loca- tion of both the topographic margins of the basin and it sub-basins; ii) the crust underlying the basin is thinner compared to the TAM (Jordan et al., 2013, Tectonophysics), but is unlikely to be strongly affected by Cretaceous or Cenozoic-age rifting, in contrast to the WAIS, which is largely underlain by the West Antarctic Rift System; iii) its bedrock is composed of rocks of different ages and composition, including Proterozoic basement, Neopro- terozoic and Cambrian sediments intruded by Cambrian arc rocks, and cover rocks formed primarily by Beacon sediments intruded by Jurassic Ferrar sills (e.g. Cook et al., 2013 Nature Geoscience). Within the framework of the collaborative Italian-US-UK BABOC project a new international initiative has been launched to analyse and model variable geological boundary conditions in the WSB using geophysical data. A large amount of new ICE- CAP aerogeophysical observations have been acquired over four campaigns over the region since the International Polar Year, in particular over the southern part of the basin, and some profiles over the northern coastal margin of the basin. We will present an initial interpretation of the potential field signatures and radar data over the northern and central parts of the basin to help establish tectonic and lithological controls on the subglacial topography and different EAIS flow regimes within the WSB

UTIG's approach to managing polar aerogeophysical data in the field: philosophy and examples from fixed wing and helicopter surveys, 27 pages, 2022.

This report documents UTIG’s approach to managing aerogeophysical data in the field. This approach to fieldwork has taken shape in the course of over 20+ years of polar campaigns based out of over 10 Antarctic stations. Aerogeophysical survey is not simply about the act of making measurements and observations. A key component of conducting surveys is managing data as it is collected and providing feedback for quality control. We want to document that institutional knowledge for the benefit of researchers who are continuing in this work as well as for the users of our data. While this document focuses on data management in the field, we start by providing the context for a typical aerogeophysical campaign and describe how the work is broken up amongst teams. We then discuss the philosophy behind field data processing, with a focus on what the goals are for preliminary processing and how it differs from the final products. With that motivation, we describe how the Base Operations team typically meets those goals, along with case studies of how we have applied this approach when based at a variety of stations and field camps, with the differing logistical challenges imposed by each. Companion documents focusing on instrumentation and airborne operations are forthcoming.Institute for Geophysic

EWU Open House Faculty Convocation

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Fisheries 9RO1R1RYHPEHUZZZÀVKHULHVRUJ GUIDELINES AND REVIEWS AFS Completes Assessment, Issues New Guidance Regarding Hatchery Operation and the Use of Hatchery-Origin Fish

BACKGROUND The American Fisheries Society (AFS) is the oldest, larg-HVW DQGPRVW LQÀXHQWLDOSURIHVVLRQDORUJDQL]DWLRQGHYRWHG WR ¿VKHULHVFRQVHUYDWLRQDQGLQWKLVFDSDFLW\WKH$)6KDVURXWLQH-ly assessed the contributions of hatcheries to natural resource management and issued recommendations to guide natural re-VRXUFHPDQDJHUV LQEHVW XVHVRI KDWFKHU\RULJLQ¿VK)RU WKH past several decades, the Society has explored these issues in a formalized process conducted at approximately 10-year in-tervals to assess contemporary issues related to hatcheries and management of aquatic resources. Representatives of the Fish Culture and Fisheries Management Sections came together in WRDQVZHUWKHTXHVWLRQ)LVKFXOWXUH¿VKPDQDJHPHQW¶V ally? ” in a symposium entitled “The Role of Fish Culture in Fisheries Management. ” In 1994, AFS reexamined the issue