Showing 11868 items
25 June, 2021 by Tracey Dornan, Claire Waluda, Ryan Saunders, Tracey Dornan, Tracey Dornan
Southern Ocean ecosystems are globally important and vulnerable to global drivers of change, yet they remain challenging to study. Fish and squid make up a significant portion of the biomass…Read more on Productivity and change in fish and squid in the Southern Ocean
25 June, 2021 by Simon Morley
St Helena is an isolated oceanic island located in the tropical South Atlantic, and knowledge of broadscale oceanography and productivity in its surrounding waters is limited. This study used model…
24 June, 2021 by Claire Waluda, David Barnes, Huw Griffiths, Jennifer Jackson, Kevin Hughes, Simon Morley, Susie Grant
Local drivers are human activities or processes that occur in specific locations, and cause physical or ecological change at the local or regional scale. Here, we consider marine and land-derived…
23 June, 2021 by Danielle Buss, Jennifer Jackson
Southern right whale vocalizations were recorded concurrently with visual observations off the sub-Antarctic Island of South Georgia, and the characteristics of these calls were described. Calls were also compared to…Read more on Southern right whale vocalizations on foraging grounds in South Georgia
23 June, 2021
Rawls argued that fairness in human societies can be achieved if decisions about the distribution of societal rewards are made from behind a veil of ignorance, which obscures the personal…Read more on A veil of ignorance can promote fairness in a mammal society
21 June, 2021 by Richard Hindmarsh, Richard Hindmarsh
Palaeo-ice sheets are important analogues for understanding contemporary ice sheets, offering a record of ice sheet behaviour that spans millennia. There are two main approaches to reconstructing palaeo-ice sheets. Empirical…21 June, 2021 by Eugene Murphy, Nadine Johnston, Rachel Cavanagh
Successful management and mitigation of marine challenges depends on cooperation and knowledge sharing which often occurs across culturally diverse geographic regions. Global ocean science collaboration is therefore essential for developing…17 June, 2021 by Emma Young, Martin Collins
Seamounts have long been recognised as hotspots for pelagic productivity and diversity in the world’s open ocean habitats. Recent studies have suggested that productivity may vary greatly between different seamounts,…
16 June, 2021 by Anje-Margriet Neutel, Michael Thorne
To assess which ecosystems are most vulnerable it is necessary to compare the resilience of complex interaction networks in a meaningful way. A fundamental problem for the comparative analysis of…16 June, 2021 by Lloyd Peck, Peter Convey, Peter Fretwell
Snow algae are an important group of terrestrial photosynthetic organisms in Antarctica, where they mostly grow in low lying coastal snow fields. Reliable observations of Antarctic snow algae are difficult…
15 June, 2021 by Kelly Hogan
The cryospheric response to climatic warming responsible for recent Arctic sea ice decline can be elucidated using marine geological archives which offer an important long-term perspective. The Holocene Thermal Maximum,…Read more on Seasonal sea ice persists through the Holocene Thermal Maximum at 80°N
14 June, 2021 by Hamish Pritchard
The IPCC Special Report on Oceans and Cryosphere in a Changing Climate identified major gaps in our knowledge of snow and glacier ice in the terrestrial cryosphere. These gaps are…Read more on Global data gaps in our knowledge of the terrestrial cryosphere
11 June, 2021 by Claire Allen, Elaine Mawbey, Povl Abrahamsen, Claus-Dieter Hillenbrand, James Smith, Victoria Peck
The West Antarctic Ice Sheet (WAIS) is one of the largest potential sources of future sea-level rise, with glaciers draining the WAIS thinning at an accelerating rate over the past…
11 June, 2021 by Joanne Johnson, Stephen Roberts
Since the Last Glacial Maximum ∼20,000 years ago, the Antarctic Ice Sheet has undergone extensive changes, resulting in a much smaller present‐day configuration. Improving our understanding of basic physical processes…
11 June, 2021 by Peter Convey
The extensive industrial use of the heavy metal molybdenum (Mo) has led to an emerging global pollution with its traces that can even be found in Antarctica. In response, a…
11 June, 2021 by Clara Manno, Kirstie Jones-Williams, Victoria Peck
As the remote Canadian Arctic Archipelago (CAA) becomes increasingly connected to the rest of the world, there is an impetus to monitor the possible impact of this connectivity. The potential…
11 June, 2021 by Mark Barham, Pierre Dutrieux
Speedup of Pine Island Glacier over the past several decades has made it Antarctica’s largest contributor to sea-level rise. The past speedup is largely due to grounding-line retreat in response…Read more on Ice-shelf retreat drives recent Pine Island Glacier speedup
11 June, 2021 by Peter Convey
As part of the reconstruction of the Brazilian Antarctic Station on King George Island, three areas of moss carpet were transplanted to minimize the impact of the new facilities on…
10 June, 2021 by Andrew Orr
Polar stratospheric clouds (PSCs) play important roles in stratospheric ozone depletion during winter and spring at high latitudes (e.g., the Antarctic ozone hole). PSC particles provide sites for heterogeneous reactions…
10 June, 2021 by Tracy Moffat-Griffin
An unusual sudden stratospheric warming (SSW) event occurred in the Southern Hemisphere in September 2019. Ground-based and satellite observations show the presence of transient eastward- and westward-propagating quasi-10 day planetary…
10 June, 2021 by Tracy Moffat-Griffin
The mesosphere and lower thermosphere (MLT) is a critical region that must be accurately reproduced in general circulation models (GCMs) that aim to include the coupling between the lower and…10 June, 2021 by Melody Clark, Tejaswi Yarra
Biomineralization by molluscs involves regulated deposition of calcium carbonate crystals within a protein framework to produce complex biocomposite structures. Effective biomineralization is a key trait for aquaculture, and animal resilience…9 June, 2021 by Richard Phillips
Research into the patterns and drivers of juvenile migration is important for understanding the development of individual migration strategies. Although several recent studies have tracked adult large gulls throughout the…
4 June, 2021 by Jakob Thyrring
1. Temperatures in the Arctic are increasing at a faster pace than at lower latitudes resulting in range expansion of boreal species. In Greenland, the warming also drives accelerating melt…
4 June, 2021 by Carlos Martin Garcia, Hugh Corr
Water-stable isotopes in polar ice cores are a widely used temperature proxy in paleoclimate reconstruction, yet calibration remains challenging in East Antarctica. Here, we reconstruct the magnitude and spatial pattern…Read more on Antarctic surface temperature and elevation during the Last Glacial Maximum
3 June, 2021 by David Barnes, Lloyd Peck, Nadescha Zwerschke, Simon Morley
All coastal systems experience disturbances and many across the planet are under unprecedented threat from an intensification of a variety of stressors. The West Antarctic Peninsula is a hotspot of…3 June, 2021 by Peter Convey
Hydrocarbon pollution is widespread around the globe and, even in the remoteness of Antarctica, the impacts of hydrocarbons from anthropogenic sources are still apparent. Antarctica’s chronically cold temperatures and other…2 June, 2021 by Peter Convey
Pollution associated with petrogenic hydrocarbons is increasing in Antarctica due to a combination of increasing human activity and the continent’s unforgiving environmental conditions. The current study focuses on the ability…2 June, 2021 by Kevin Newsham
Previous studies have shown changes to the frequencies of hyphal coils and other fungal structures in leafy liverwort tissues across latitudinal transects through Antarctica. Although suggestive of a role of…
1 June, 2021 by Philip Trathan, Peter Fretwell
The distribution of emperor penguins is circumpolar, with 54 colony locations currently reported of which 50 are currently extant as of 2019. Here we report on eight newly discovered colonies…Read more on Discovery of new colonies by Sentinel2 reveals good and bad news for emperor
1 June, 2021 by Huw Griffiths, Lloyd Peck
Important findings from the second decade of the 21st century on the impact of environmental change on biological processes in the Antarctic were synthesised by 26 international experts. Ten key…Read more on Antarctic ecosystems in transition – life between stresses and opportunities
1 June, 2021 by Gareth Chisham
The high frequency radars in the Super Dual Auroral Radar Network (SuperDARN) estimate the elevation angles of returned backscatter using interferometric techniques. These elevation angles allow the ground range to…
1 June, 2021 by Huw Griffiths
Quantarctica (https://www.npolar.no/quantarctica) is a geospatial data package, analysis environment, and visualization platform for the Antarctic Continent, Southern Ocean (>40oS), and sub-Antarctic islands. Quantarctica works with the free, cross-platform Geographical Information…
1 June, 2021 by Andrew Orr, Gareth Marshall, Hua Lu, Scott Hosking, John King, John Turner, Steve Colwell, Tony Phillips
Commencing in 1956, observations made at Halley Research Station, Antarctica provide one of the longest continuous series of near-surface temperature observations from the Antarctic continent. Since few other records of…Read more on Inhomogeneity of the surface air temperature record from Halley, Antarctica
1 June, 2021 by Kevin Hughes, Peter Convey
Antarctica currently has few non-native species, compared to other regions of the planet, due to the continent’s isolation, extreme climatic conditions and the lack of habitat. However, human activity, particularly…
1 June, 2021 by Martin Collins
The yellowfin tuna (Thunnus albacares) is a widely distributed, migratory species that supports valuable commercial fisheries throughout their range. Management of migratory species requires knowledge of movement, mixing and key…
1 June, 2021 by Teal Riley
We present the results of U-Pb zircon dating conducted using laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), isotopic tracing analyses of Hf in zircon and Sr-Nd in whole-rock and whole-rock…
1 June, 2021 by Kevin Hughes, Susie Grant
Antarctic ecosystem services are rich and diverse and include global climate modulation, biodiversity and habitat protection, cultural heritage, scientific knowledge, education and recreation as well as the extraction of marine…1 June, 2021 by Hugh Venables, Alexander Brearley, Mark Barham, Michael Meredith
The west Antarctic Peninsula (WAP) is a region of marked climatic variability, exhibiting strong changes in sea ice extent, retreat of most of its glaciers, and shifts in the amount…
1 June, 2021 by Eugene Murphy, John Dickens, Martin Collins, Philip Hollyman, Philip Trathan, John Dickens
Many remote islands present barriers to effective wildlife monitoring in terms of challenging terrain and frequency of visits. The sub-Antarctic islands of South Georgia and the South Sandwich Islands are…
1 June, 2021 by Irena Vankova
High-frequency radar tracking of icebergs floating in front of a glacier in Greenland show that movements of the ice mélange consistently increase before calving events, indicating that mélange has the…Read more on Calving prediction from ice mélange motion [News]
31 May, 2021 by Katrin Linse
Growing human activity in areas beyond national jurisdiction (ABNJ) is driving increasing impacts on the biodiversity of this vast area of the ocean. As a result, the United Nations General…
28 May, 2021 by Robert Mulvaney
Fire plays a pivotal role in shaping terrestrial ecosystems and the chemical composition of the atmosphere and thus influences Earth’s climate. The trend and magnitude of fire activity over the…28 May, 2021 by Philip Trathan
Climate change and other human activities are causing profound effects on marine ecosystem productivity. We show that the breeding success of seabirds is tracking hemispheric differences in ocean warming and…Read more on Hemispheric asymmetry in ocean change and the productivity of ecosystem sentinels
28 May, 2021 by Sandra McInnes, Sandra McInnes
Over the last two decades, Zootaxa has hosted nearly 200 papers concerning tardigrade taxonomy, systematics, phylogeny, and evolution. A total of 160 researchers from all continents (except the Antarctic) published…Read more on 20 years of Zootaxa: Tardigrada (Ecdysozoa: Panarthropoda).
28 May, 2021 by Martin Collins
The yellowfin tuna (Thunnus albacares: YFT) is a widely distributed, migratory species that supports valuable commercial fisheries. Landings of YFT are seasonally and spatially variable, reflecting changes in their availability…27 May, 2021
Gravity wave (GW) activities in the upper mesosphere (80–100 km) and their potential sources are investigated using meteor radar observations at King Sejong Station, Antarctica (KSS; 62.22°S, 58.78°W) during recent…
26 May, 2021 by Mervyn Freeman
We must be able to predict and mitigate against GIC effects to minimize socio‐economic impacts. This study employs the Space Weather Modeling Framework (SWMF) to model the geomagnetic response over…25 May, 2021 by Louis-Alexandre Couston
Subglacial lakes are isolated, low-temperature and high-pressure water environments hidden under ice sheets. Here, we use two-dimensional direct numerical simulations in order to investigate the characteristic temperature fluctuations and velocities…
20 May, 2021 by Keith Nicholls, Peter Davis
Floating ice shelves are the Achilles’ heel of the Antarctic Ice Sheet. They limit Antarctica’s contribution to global sea level rise, yet they can be rapidly melted from beneath by…
20 May, 2021 by Peter Convey
Hydrocarbons can cause pollution to Antarctic terrestrial and aquatic ecosystems, both through accidental release and the discharge of waste cooking oil in grey water. Such pollutants can persist for long…20 May, 2021 by John King, Tracy Moffat-Griffin
Atmospheric gravity waves (GWs) play an important role in atmospheric dynamics but accurately representing them in general circulation models (GCMs) is challenging. This is especially true for orographic GWs generated…
19 May, 2021 by Peter Convey
Two new mite species belonging to the genus Stereotydeus Berlese, 1901 were discovered from locations along the coast of Victoria Land, continental Antarctica. Previous records of this genus in the…
18 May, 2021 by Andrew Orr, Gareth Marshall, Hua Lu, Thomas Bracegirdle
This study quantifies differences among four widely used atmospheric reanalysis datasets (ERA5, JRA-55, MERRA-2, and CFSR) in their representation of the dynamical changes induced by springtime polar stratospheric ozone depletion…
17 May, 2021 by Michael McCarthy, Michael McCarthy
Glaciers in High Mountain Asia generate meltwater that supports the water needs of 250 million people, but current knowledge of annual accumulation and ablation is limited to sparse field measurements…Read more on Health and sustainability of glaciers in High Mountain Asia
16 May, 2021 by Mark Clilverd
For many years, it was believed that resonant interactions between electromagnetic ion cyclotron (EMIC) waves and radiation belt electrons were restricted to electron energies > 1 − 2 MeV. In…Read more on Evidence of sub‐MeV EMIC‐driven trapped electron flux dropouts from GPS observations
15 May, 2021 by Jakub Stocek
We propose an operator preconditioner for general elliptic pseudodifferential equations in a domain Ω, where Ω is either in Rn or in a Riemannian manifold. For linear systems of equations…Read more on Optimal operator preconditioning for pseudodifferential boundary problems.
13 May, 2021 by Deb Shoosmith
Hydrographic data are analyzed for the broad continental shelf of the Bellingshausen Sea, which is host to a number of rapidly‐thinning ice shelves. The flow of warm Circumpolar Deep Water…Read more on Ice‐shelf meltwater overturning in the Bellingshausen Sea
13 May, 2021 by David Barnes, Huw Griffiths, Simon Morley
Knowledge of life on the Southern Ocean seafloor has substantially grown since the beginning of this century with increasing ship-based surveys and regular monitoring sites, new technologies and greatly enhanced…
7 May, 2021 by Tracy Moffat-Griffin
Sudden Stratospheric Warmings (SSWs) could act as an important mediator in the vertical coupling of atmospheric regions and dramatic variations in the mesosphere and lower thermosphere (MLT) in response to…6 May, 2021 by Peter Convey
Two cyanobacterial morphotypes isolated from Signy Island, South Orkney Islands, maritime Antarctica were characterised using a polyphasic approach combining morphological, cytological and molecular analyses. These analyses showed that the strains…
5 May, 2021 by Louise Sime
Improving the understanding of changes in the mean and variability of climate variables as well as their interrelation is crucial for reliable climate change projections. Comparisons between general circulation models…
5 May, 2021 by Philip Hollyman
Using growth rings observed in statoliths, the size-at-age relationship was modeled for waved whelk (Buccinum undatum) populations within the Mid-Atlantic Bight. A total of 45 sites in the Mid-Atlantic were…
5 May, 2021 by Robert Mulvaney
We present novel measurements of the carbon isotope composition of CFC-11 (CCl3F), CFC-12 (CCl2F2), and CFC-113 (CF2ClCFCl2), three atmospheric trace gases that are important for both stratospheric ozone depletion and…5 May, 2021 by Joseph Ulanowski
This paper presents measurements of mineral dust concentration in the diameter range from 0.4 to 14.0 µm with a novel balloon-borne optical particle counter, the Universal Cloud and Aerosol Sounding System…
1 May, 2021 by Povl Abrahamsen
Deploying long‐range autonomous underwater vehicles (AUVs) mid‐water column in the deep ocean is one of the most challenging applications for these submersibles. Without external support and speed over the ground…Read more on Terrain-aided navigation for long-range AUVs in dynamic under-mapped environments
1 May, 2021 by Jakob Thyrring, Lloyd Peck, Melody Clark
The Arctic is experiencing particularly rapid rates of warming, consequently invasive boreal species are now able to survive the less extreme Arctic winter temperatures. Whilst persistence of intertidal and terrestrial…Read more on Resilience in Greenland intertidal Mytilus: The hidden stress defense
1 May, 2021 by Hugh Venables, Alexander Brearley, Michael Meredith, Ryan Scott
Quantifying and understanding the processes driving turbulent mixing around Antarctica is key to closing the Southern Ocean’s heat budget, an essential component of the global climate system. In 2016, a…1 May, 2021 by Geraint Tarling, Gabriele Stowasser, Ryan Saunders, Sophie Fielding
Indicators of oxidative stress and metabolic capacity are key factors in understanding the fitness of wild populations. In the present study, these factors were evaluated in the pelagic Southern Ocean…1 May, 2021 by Peter Convey
We assessed the diversity of fungal DNA present in sediments of three lakes on Vega Island, north-east Antarctic Peninsula using metabarcoding through high-throughput sequencing (HTS). A total of 640,902 fungal…1 May, 2021 by Andrew Kavanagh, Ingrid Cnossen
Orbital data from the year 1967 onwards has allowed for historical observations of the thermosphere, and has shown a long-term decrease in atmospheric density at LEO altitudes of around -1.7…1 May, 2021 by Amy King, Dieter Tetzner
New ice-core records are being developed from the sub-Antarctic, a region previously lacking in paleoclimate archives. These records capture marine-sourced organic compounds that act as proxies for sea-ice concentration, and…Read more on Exploring novel ice-core proxies for paleoclimate reconstruction in the sub-Antarctic
28 April, 2021 by David Vaughan, Julien Bodart
Understanding the contribution of the West Antarctic Ice Sheet (WAIS) to past and future sea level has been a major scientific priority over the last three decades. In recent years,…
28 April, 2021 by Andrew Meijers, Dani Jones, Emma Boland
The Southern Ocean (SO) is a crucial region for the global ocean uptake of heat and carbon. There are large uncertainties in the observations of fluxes of heat and carbon…
28 April, 2021 by Ella Gilbert
The future surface mass balance (SMB) of Antarctic ice shelves has not been constrained with models of sufficient resolution and complexity. Here, we force the high‐resolution Modèle Atmosphérique Régional (MAR)…28 April, 2021 by Michael McCarthy, Michael McCarthy
Glacier albedo determines the net shortwave radiation absorbed at the glacier surface and plays a crucial role in glacier energy and mass balance. Remote sensing techniques are efficient means to…
27 April, 2021 by Andrew Kavanagh, Ingrid Cnossen
Increasing carbon dioxide causes cooling in the upper atmosphere and a secular decrease in atmospheric density over time. With the use of the Whole Atmospheric Community Climate Model with thermosphere…
27 April, 2021 by Mark Clilverd, Mervyn Freeman
Measurements from six longitudinally separated magnetic observatories, all located close to the 53⁰ mid-latitude contour, are analysed. We focus on the large geomagnetic 16 disturbance that occurred during 7 and…22 April, 2021 by Kayleigh Jones
Concerns have recently been raised as to whether small harbour seal pups found alone are genuine 'orphans', i.e. pups permanently separated from their mother. We present records of body mass…19 April, 2021 by Carlos Martin Garcia, Robert Mulvaney
The area near Dome C, East Antarctica, is thought to be one of the most promising targets for recovering a continuous ice-core record spanning more than a million years. The…
16 April, 2021 by Irena Vankova, Keith Nicholls
A phase‐sensitive radar (ApRES) was deployed on Totten Ice Shelf to provide the first in‐situ basal melt estimate at this dynamic East Antarctic ice shelf. Observations of internal ice dynamics…16 April, 2021 by Mark Clilverd
VLF radio propagation recordings are used to determine the characteristics of the nighttime polar lower D region of the ionosphere. Recordings of both VLF phase and amplitude in the Arctic…Read more on Quiet night Arctic ionospheric D region characteristics
15 April, 2021 by Geraint Tarling, Gabriele Stowasser, Richard Phillips, Ryan Saunders, Susan Gregory, Sophie Fielding
Biomagnification of mercury (Hg) in the Scotia Sea food web of the Southern Ocean was examined using the stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) as proxies for…Read more on Mercury biomagnification in a Southern Ocean food web
9 April, 2021 by Kelly Hogan, Robert Larter
Thwaites Glacier is the most rapidly changing outlet of the West Antarctic Ice Sheet and adds large uncertainty to 21st century sea-level rise predictions. Here, we present the first direct…9 April, 2021 by Paul Anker
Icefin is a custom designed remotely or autonomously operated vehicle (ROV/AUV) for sub-ice deployments in polar environments with a primary focus on modularity for deploying multiple payloads throughout a season…Read more on Antarctic Deep Field Deployments and Design of the Icefin ROV
8 April, 2021 by Richard Horne
Severe space weather was identified as a risk to the UK in 2010 as part of a wider review of natural hazards triggered by the societal disruption caused by the…8 April, 2021 by Jakob Thyrring, Lloyd Peck
Whether global latitudinal diversity gradients exist in rocky intertidal a-diversity and across functional groups remains unknown. Using literature data from 433 intertidal sites, we investigated α-diversity patterns across 155° of…Read more on Global gradients in intertidal species richness and functional groups
5 April, 2021 by Scott Hosking
The most mature aspect of applying artificial intelligence (AI)/machine learning (ML) to problems in the atmospheric sciences is likely post-processing of model output. This article provides some history and current…1 April, 2021 by Richard Phillips, William Mills
The non‐breeding period is critical for restoration of body condition and self‐maintenance in albatrosses, yet detailed information on diet and distribution during this stage of the annual cycle is lacking…
1 April, 2021 by Carrie Gunn, Richard Phillips
Young birds in cold environments face a range of age-specific thermal challenges. Studying the thermal biology of young birds throughout ontogeny may further our understanding of how such challenges are…1 April, 2021 by Oliver Marsh
Fox Glacier/Te Moeka o Tuawe is a fast-responding maritime glacier that has undergone multiple advance and retreat phases during recent decades. Here we use a combination of repeat photography, Structure…
1 April, 2021 by Hamish Pritchard, Steve Colwell
The seasonal snowpack is a globally important water resource that is notoriously difficult to measure. Existing instruments make measurements of falling or accumulating snow water equivalent (SWE) that are susceptible…1 April, 2021 by Gareth Marshall, Hua Lu, John King, John Turner, Steve Colwell, Tony Phillips
We present the first Antarctic-wide analysis of extreme near-surface air temperatures based on data collected up to the end of 2019 as part of the synoptic meteorological observing programs. We…
1 April, 2021 by Dominic Hodgson
Terrestrial biota in the Antarctic are more globally distinct and highly structured biogeographically than previously believed, but information on biogeographic patterns and endemism in freshwater communities is largely lacking. We…Read more on Diatoms define a novel freshwater biogeography of the Antarctic
1 April, 2021 by Povl Abrahamsen
Water-mass transformation by turbulent mixing is a key part of the deep-ocean overturning, as it drives the upwelling of dense waters formed at high latitudes. Here, we quantify this transformation…Read more on Mixing and transformation in a deep western boundary current: A case study
1 April, 2021 by Teal Riley
Late Triassic – Jurassic igneous rocks of the Antarctic Peninsula and Patagonia provide evidence for the evolution of the margin of southwestern Gondwana. We present new geochronological (LAICP-MS zircon U-Pb…
1 April, 2021 by Claire Allen, Claus-Dieter Hillenbrand, Robert Larter
The Antarctic Peninsula’s Pacific margin is one of the best studied sectors of the Antarctic continental margin. Since the 1990s, several research cruises have targeted the continental rise with geophysical…
1 April, 2021 by Elaine Fitzcharles, Martin Collins, Philip Hollyman
Fishes of the genus Muraenolepis are regularly caught in commercial and research fishing in the waters around South Georgia and the South Sandwich Islands, but for many years there has…1 April, 2021 by James France
The rising number of operational biogas plants in the UK brings a new emissions category to consider for methane monitoring, quantification and reduction. Minimising methane losses from biogas plants to…Read more on Quantification of methane emissions from UK biogas plants