Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics
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Polar Ocean Mixing by Internal Tsunamis (POLOMINTS)
Get PDFMixing of the ocean around Antarctica is a key process that exerts influences over large scales and in multiple ways. By redistributing heat in the ocean, it exerts strong influences on the Antarctic Ice Sheet, with implications for sea level rise globally. Similarly, the redistribution of ocean heat affects the production of sea ice in winter and its melt in summer, with consequences for climate. Mixing also affects the distribution of nutrients in the ocean, with direct impacts on the marine ecosystem and biodiversity and with consequences for fisheries.
It was long thought that mixing of the seas close to Antarctica was predominantly caused by winds, tides and the loss of heat from the ocean especially in winter. However, we recently discovered that when glaciers calve in Antarctica, they can trigger underwater tsunamis. These are large (multi-metre) waves that move rapidly away from the coastline and when they break, they cause sudden bursts of very intense mixing. Simple calculations indicated that the net impact of these underwater tsunamis could be as strong as winds, and much more important than tides, in driving mixing. It was also argued that they are likely to be relevant everywhere that glaciers calve into the sea, including Greenland and across the Arctic. As our ocean and atmosphere continue to heat up, it is very possible that glacier calving will become more frequent and intensify, increasing further the impact of underwater tsunamis on large-scale climate, the cryosphere and ecosystems.
This is an exciting new avenue of scientific investigation and many key questions remain unanswered. We need to know how widespread and frequent the generation of underwater tsunamis is, how far they travel from the coastline before breaking, and how variable this is. We need to measure what impacts the extra mixing has on ocean temperature and nutrient concentrations, and to determine what this means for the cryosphere and ocean productivity. There is a pressing need to include the effects of underwater tsunamis in the computer models that are used for projecting future ocean climate and ecosystem conditions and to determine the feedbacks between climate change and the generation of more underwater tsunamis.
To answer these questions, our project will deploy innovative techniques for measuring the ocean and ice in close proximity to a calving glacier, including robotic underwater vehicles and remotely-piloted aircraft, and cutting-edge deep-learning techniques applied to satellite data. We will use advanced computer simulations to fully understand the causal mechanisms responsible for the creation and spread of the underwater tsunamis and their impacts on ocean climate and marine productivity. We will make our developments in computer simulation available to the whole community of users, for widespread uptake and future use.
This project will have significant benefits for academics seeking to predict the future of Antarctica and its impacts on the rest of the world, for Governments and intergovernmental agencies seeking to understand how best to respond to climate change, and for the curious general public wanting to learn more about the extremes of the planet and why they matter. The fieldwork will be especially photo- and video-genic and will lead to outstanding outreach and impact opportunities, and we will work with media agencies seeking to tell compelling stories about the extremes of the Earth
The role of transaction costs for the optimal supply of carbon sequestration from cover crops in Denmark
Get PDFClimate change suggests the use of carbon dioxide removal technologies, such as soil carbon sequestration in agriculture, to complement mitigation efforts. However, there could be challenges with implementing sequestration measures due to transaction costs, such as farm expenses for research, information, and planning. The purpose of this study is to investigate how transaction costs affect the cost-effective supply of carbon sequestration from cover crops in Denmark. We develop a model of the optimal adoption of cover crops, accounting for farm spatial heterogeneity and potentially nonlinear transaction costs to adoption. In the presence of transaction costs and at a carbon price of 220 €/tCO2e (suggested as an appropriate level of a CO2e tax for Danish agriculture) increased cover crop cultivation will only offset 15.4 tCO2e per year, corresponding to 0.002% of the Danish agricultural emissions reduction target. Assuming zero transaction costs overestimates the annual sequestration supply at the given price by 13,030 tCO2e. Total abatement and transaction costs for cover cropping are on average 78 € per ha and transaction costs can represent up to 90% of total costs for low carbon prices. Transaction costs also alter the cost-effective distribution of carbon sequestration across space and farm size groups
Subduction and melting of biogenic and ferromanganese sediments as evidenced by sub-Moho granitoids
Get PDFMantle-hosted granitoids (MHG) from the supra-subduction Samail ophiolite in Oman and the United Arab Emirates exhibit diverse compositions, highlighting variations in petrogenesis and source contributions. Previous isotopic data indicate these MHG originated through the interaction of sediment-derived with basaltic melts from an underthrust oceanic plate within the mantle wedge. The sedimentary contribution was attributed to the partial melting of pelitic to siliceous (bio-siliceous) material atop the subducted plate based on elevated zircon δ18O values (∼14–28 ‰). To further evaluate this hypothesis on Samail MHG petrogenesis and source contribution, we present new and compiled radiogenic (Sr-Nd-Hf-Pb) and stable (O-Li-H) isotopes, along with zircon trace element analyses. The variable Sr and Pb isotopic signature support a mixed origin involving altered mafic and sedimentary sources in the formation of the MHG. Negative whole-rock εNd, coupled with elevated δ7Li in muscovite suggest the involvement of sedimentary sources and particularly those resembling deep-sea ferromanganese-rich sediments. We propose a new model identifying ferromanganese sediments as a potential source given their widespread distribution across the ocean floor, broad range of δ18O (up to 29.5 ‰), slightly positive Hf values, seawater-like δ7Li signatures (median of ∼27 ‰), and zircon trace element compositions lacking a signature of monazite co-precipitation, which match the signatures required for the genesis of the Samail MHG. Preservation of oceanic lithosphere in the geological record is limited, and MHG in ophiolites are uncommon. Therefore, the Samail MHG are key examples of crustal materials transported to the mantle, with implications for mantle heterogeneity and arc mantle redox budget
Using expert elicitation to assess the likely effectiveness of conservation interventions during an unprecedented outbreak of high pathogenicity avian influenza (HPAI) in wild birds
No full text•Capsule: Six months into an unprecedented high pathogenicity avian influenza outbreak in wild birds, expert elicitation highlighted significant uncertainty in the likely effectiveness of interventions to reduce the population-level impact, although carcass removal and vaccination of wild birds were scored as most likely to be beneficial.
•Aims: To assess the potential effectiveness of a range of interventions to reduce the impact of high pathogenicity avian influenza upon wild bird populations.
•Methods: Participants assessed risk for different species groups and scored the likely impact of different interventions on the probability of wild populations suffering high mortality from avian influenza (defined as five or more dead individuals clustered at a colony/population) through a modified expert elicitation approach during a virtual workshop.
•Results: Estimates of mortality and responses to interventions were highly uncertain. Seabirds and wildfowl were regarded as being at greatest risk of high mortality. The top two interventions as ranked by participants were carcass removal (particularly for raptors, seabirds and other vulnerable species) and vaccination. Both interventions were regarded with high uncertainty and likely to only be feasible in certain circumstances. Measures to reduce the possible effects of research or other activities in the countryside were regarded as unlikely to have an impact on viral spread and mortality.
•Conclusion; No conservation interventions were identified as likely to result in a large reduction of the risk of high mortality in wild birds from avian influenza. The two most likely candidates, carcass removal and vaccination, both have significant practical challenges, but may work in some circumstances and therefore warrant further testing. Restrictions on research activities, including ringing and tagging, may be counter-productive by reducing the evidence available to understand the impacts and inform wild bird conservation
Source dynamics of Ruapehu’s 2022 volcanic unrest: insights from drumbeat seismicity, tremor, and crater lake signals
Get PDFRuapehu, one of Aotearoa New Zealand’s most active andesitic volcanoes, experienced moderate to heightened volcanic unrest beginning March 2022. This included heightened volcanic tremor, the initiation of a new heating phase at the crater lake Te Wai ā-moe, and increases in gas emissions. The unrest featured highly periodic, low-frequency earthquakes known as ‘drumbeats’. These signals have been observed around the world to often precede and/or accompany the ascent of magma and volcanic eruptions. However, Ruapehu did not erupt in 2022. In this work, approximately 43,000 discrete drumbeat events and 89 days of continuous volcanic tremor were identified over the 121-day unrest period. These were analysed in the time, amplitude, and frequency domains. We argue that increases in volcanic tremor, lake temperatures, and gas throughput are the result of magma ascent into the shallow system immediately prior to or contemporaneous with the onset of tremor. We construct a conceptual model for the generation of drumbeat, tremor, and lake temperature signals that consists of shallow magma storage, a gas cavity, a permeable cap, and the crater lake. The presence of repetitive drumbeat earthquakes results from transient sealing and failure within the fracture pathways of the permeable cap. This is driven and regulated primarily by pressure accumulation from persistently degassing magma and the strength of the sealing mechanism
Brachiopods as archives of intrannual, annual, and interannual environmental variations
Get PDFBrachiopods have been employed for environmental and climatic reconstructions in the near and geological past. Traditionally, one datapoint is obtained per shell, providing time‐averaged bulk signals. However, brachiopods also have the potential to provide time‐resolved information on (sub)annual timescales, but this has been understudied due to difficulties in accounting for brachiopod shell growth. We investigated the distribution of δ 18 O, δ 13 C and Element/Ca along growth profiles of three Recent terebratulides from temperate and polar latitudes. We employed a novel approach using the Brody–Bertalanffy equation to transform shell distances into ages, permitting the study of periodicity in the measured signatures. We show that, superimposed on ontogenetic trends, faster‐growing temperate species record annual and intrannual changes at collection sites, whereas slower‐growing Antarctic species are also controlled by endogenous cycles. δ 18 O profiles reflect annual and intrannual variations in midlatitudes and interannual variations at high latitudes. δ 13 C and Element/Ca are additionally influenced by vital effects
Emerging priorities in terrestrial herbivory research in the Arctic
Get PDFHerbivores are an integral part of Arctic terrestrial ecosystems, driving ecosystem functioning and sustaining local livelihoods. In the context of accelerated climate warming and land use changes, understanding how herbivores contribute to the resilience of Arctic socio-ecological systems is essential to guide sound decision-making and mitigation strategies. While research on Arctic herbivory has a long tradition, recent literature syntheses highlight important geographical, taxonomic and environmental knowledge gaps on the impacts of herbivores across the region. At the same time, climate change and limited resources impose an urgent need to prioritize research and management efforts. We conducted a horizon scan within the Arctic herbivory research community to identify emerging scientific and management priorities for the next decade. From 288 responses received from 85 participants in two online surveys and an in-person workshop, we identified 8 scientific and 8 management priorities centred on: a) understanding and integrating fundamental ecological processes across multiple scales from individual herbivore-plant interactions up to regional and decadal scale vegetation and animal population effects; b) evaluating climate change feedbacks; and c) developing new research methods. Our analysis provides a strategic framework for broad, inclusive, interdisciplinary collaborations to optimise terrestrial herbivory research and sustainable management practices in a rapidly changing Arctic
Human system impacts of overshoot pathways. Global consequences of climate overshoot pathways: annex 6
Get PDFGlacial geology of the Hudson Mountains, Amundsen Sea sector, West Antarctica
Get PDFThe Hudson Mountains are situated in the eastern Amundsen Sea sector of the West Antarctic Ice Sheet, adjacent to Pine Island Glacier. They form a volcanic field of 17 stratovolcanoes and parasitic vents, preserved as nunataks. Two former tributaries of Pine Island Glacier (Larter and Lucchitta glaciers) flow through the mountains. Here we present a detailed study of the glacial geology of the area. We describe field observations and measurements of geomorphological features from 15 of the nunataks, meltwater ponds found on the surface of three nunataks and supraglacial features (ice dolines) from two sites near the present grounding line. Together these provide constraints on the past ice sheet extent, flow pathways and thermal regime, and enhance our understanding of the present hydrological regime – all of which are important as context for the observed modern ice sheet behaviour. We find evidence suggesting that all nunataks in the Hudson Mountains were covered by ice during the Last Glacial Maximum (defined here as 26.5-19 ka; Clark et al., 2009) and have since deglaciated. Faceted and polished erratic cobbles and boulders of exotic lithologies (syenites, alkali granites, granites, granodiorites, tonalites and gabbros) are numerous and perched on nunatak surfaces. A marked difference between the dominant erratic lithologies on nunataks adjacent to Pine Island Glacier (granite) and Lucchitta Glacier (granodiorite-tonalite) indicates that the ice sheet was transporting clasts from at least two distinct upstream source regions. The similarity in degree of weathering suggests, however, that all the erratics were transported by one phase of (warm-based) glaciation; their presence on or close to the summits of all except one nunatak indicates that the ice sheet during that time was at least 700 m thicker than present. These results are consistent with ice sheet model simulations which suggest that all nunataks in the Hudson Mountains were completely submerged by the Last Glacial Maximum ice sheet
Lateral Fluxes Drive Basal Melting Beneath Thwaites Eastern Ice Shelf, West Antarctica
Get PDFThwaites Glacier is one of the fastest-changing ice-ocean systems in Antarctica. Basal melting beneath Thwaites' floating ice shelf, especially around pinning points and at the grounding line, sets the rate of ice loss and Thwaites' contribution to global sea-level rise. The rate of basal melting is controlled by the transport of heat into and through the ice–ocean boundary layer toward the ice base. Here we present the first turbulence observations from the grounding line of Thwaites Eastern Ice Shelf. We demonstrate that contrary to expectations, the turbulence-driven vertical flux of heat into the ice–ocean boundary layer is insufficient to sustain the basal melt rate. Instead, most of the heat required must be delivered by lateral fluxes driven by the large-scale advective circulation. Lateral processes likely dominate beneath the most unstable warm-cavity ice shelves, and thus must be fully incorporated into parameterizations of ice shelf basal melting
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