Atmospheric drivers of surface melting on the Larsen C ice shelf, Antarctic Peninsula

Observational data and high resolution (<4 km grid spacing) Met Office Unified Model (MetUM) output is used to investigate the dominant causes of surface melting on the Larsen C ice shelf. In the first two parts of the thesis, a case study approach is used to examine the role of wintertime foehn winds and summertime cloud phase on the surface energy balance (SEB) of Larsen C, and therefore surface melting. Firstly, wintertime foehn events are shown for the first time to drive significant and unseasonal surface melting by greatly enhancing surface sensible heat fluxes. Secondly, it is demonstrated that cloud phase, and particularly liquid water content, strongly influences the SEB and surface melting. More accurate model representations of cloud phase are shown to reduce biases in SEB terms and melt. As part of this work, an optimised MetUM configuration is developed for the Antarctic Peninsula. Thirdly, the final part of the thesis presents and analyses a novel, multi-decadal (1998-2017) model hindcast for Larsen C. The hindcast reproduces observed patterns of foehn-driven melt, making it one of the first long model simulations to do so. Solar radiation is the dominant driver of melting, but cloud phase is shown to determine its extent and duration via feedbacks on temperature and energy fluxes, and foehn winds are especially important for producing melt in non-summer seasons. Large-scale patterns of climate variability like the Southern Annular Mode (SAM) establish conditions for foehn- and cloud-mediated melting to occur. This advanced understanding of processes contributing to surface melting on Larsen C establishes a baseline for future projections. If recent trends towards a more positive SAM and higher temperatures continue in future, surface melting could increase enough to destabilise the ice shelf, potentially contributing to sea level rise

2023's Antarctic sea ice extent is the lowest on record

Antarctic sea ice is a vitally important part of the regional and global climate. In 2023, sea ice extent fell to record lows, reaching unprecedented values for both the summer minimum, winter maximum and intervening freeze-up period. Here, we show that the extreme values observed were truly remarkable within the context of the satellite record, despite the challenge of quantifying how rare such an event might be, and discuss some contributing factors. While this could be part of a decline in sea ice associated with human-caused climate change, it is too early to say conclusively if this is the case

Atmospheric drivers of melt on Larsen C Ice Shelf: Surface energy budget regimes and the impact of foehn

Recent ice shelf retreat on the east coast of the Antarctic Peninsula has been principally attributed to atmospherically driven melt. However, previous studies on the largest of these ice shelves—Larsen C—have struggled to reconcile atmospheric forcing with observed melt. This study provides the first comprehensive quantification and explanation of the atmospheric drivers of melt across Larsen C, using 31-months' worth of observations from Cabinet Inlet, a 6-month, high-resolution atmospheric model simulation and a novel approach to ascertain the surface energy budget (SEB) regime. The dominant meteorological controls on melt are shown to be the occurrence, strength, and warmth of mountain winds called foehn. At Cabinet Inlet, foehn occurs 15% of the time and causes 45% of melt. The primary effect of foehn on the SEB is elevated turbulent heat fluxes. Under typical, warm foehn conditions, this means elevated surface heating and melting, the intensity of which increases as foehn wind speed increases. Less commonly—due to cooler-than-normal foehn winds and/or radiatively warmed ice—the relationship between wind speed and net surface heat flux reverses. This explains the seemingly contradictory results of previous studies. In the model, spatial variability in cumulative melt across Larsen C is largely explained by foehn, with melt maxima in inlets reflecting maxima in foehn wind strength. However, most accumulated melt (58%) occurs due to solar radiation in the absence of foehn. A broad north-south gradient in melt is explained by the combined influence of foehn and non-foehn conditions

Summertime cloud phase strongly influences surface melting on the Larsen C ice shelf, Antarctica

Surface melting on Antarctic Peninsula ice shelves can influence ice shelf mass balance, and consequently sea level rise. We show that summertime cloud phase on the Larsen C ice shelf on the Antarctic Peninsula strongly influences the amount of radiation received at the surface and can determine whether or not melting occurs. While previous work has separately evaluated cloud phase and the surface energy balance (SEB) during summertime over Larsen C, no previous studies have examined this relationship quantitatively. Furthermore, regional climate models frequently produce surface radiation biases related to cloud ice and liquid water content. This study uses a high-resolution regional configuration of the UK Met Office Unified Model (MetUM) to assess the influence of cloud ice and liquid properties on the SEB, and consequently melting, over the Larsen C ice shelf. Results from a case-study show that simulations producing a vertical cloud phase structure more comparable to aircraft observations exhibit smaller surface radiative biases. A configuration of the MetUM adapted to improve the simulation of cloud phase reproduces the observed surface melt most closely. During a five-week simulation of summertime conditions, model melt biases are reduced to <2 W·m −2: a four-fold improvement on a previous study that used default MetUM settings. This demonstrates the importance of cloud phase in determining summertime melt rates on Larsen C

Pattern of hospital referrals of children at risk of maltreatment

ABSTRACT Background Increasingly emergency departments (ED) and other acute services in the hospital provide first access care, especially out of hours and for poorer families. Studies of detection of child maltreatment in the hospital have focused on children presenting with injury, although maltreatment may be suspected when parents present to the hospital with problems related to violent behaviour, drug abuse or mental health problems. Methods A consecutive case series is described of patients referred for suspected child maltreatment from one inner-city general hospital after training was given to clinical staff and 2 years after the creation of a new post comprising a full-time, experienced child protection advisor (CPA) on-site to support clinicians with concerns about child maltreatment. Results There were 44 referrals to the CPA over 2 months in 2005, of whom just under half were initiated by clinicians caring for a parent. 15 referrals came from the ED (five followed a parent presenting to the ED), 14 from maternity obstetric services, and 15 from the neonatal or paediatric wards. Most families (38; 86%) were referred by nurses. One-quarter of referrals were already known to children&apos;s social care. Conclusions Clinicians need to be aware that half the vulnerable children in hospital are identified through one or other parent. It is hypothesised that the availability of an experienced child protection advisor on-site, combined with child protection training, makes it possible for clinicians caring for adults with problems related to violence, drug abuse or acute mental illness, to take action to address the potential vulnerability of their children

Evaluating the clinical and cost effectiveness of a behaviour change intervention for lowering cardiovascular disease risk for people with severe mental illnesses in primary care (PRIMROSE study):study protocol for a cluster randomised controlled trial

BACKGROUND: People with severe mental illnesses die up to 20 years earlier than the general population, with cardiovascular disease being the leading cause of death. National guidelines recommend that the physical care of people with severe mental illnesses should be the responsibility of primary care; however, little is known about effective interventions to lower cardiovascular disease risk in this population and setting. Following extensive peer review, funding was secured from the United Kingdom National Institute for Health Research (NIHR) to deliver the proposed study. The aim of the trial is to test the effectiveness of a behavioural intervention to lower cardiovascular disease risk in people with severe mental illnesses in United Kingdom General Practices. METHODS/DESIGN: The study is a cluster randomised controlled trial in 70 GP practices for people with severe mental illnesses, aged 30 to 75 years old, with elevated cardiovascular disease risk factors. The trial will compare the effectiveness of a behavioural intervention designed to lower cardiovascular disease risk and delivered by a practice nurse or healthcare assistant, with standard care offered in General Practice. A total of 350 people will be recruited and followed up at 6 and 12 months. The primary outcome is total cholesterol level at the 12-month follow-up and secondary outcomes include blood pressure, body mass index, waist circumference, smoking status, quality of life, adherence to treatments and services and behavioural measures for diet, physical activity and alcohol use. An economic evaluation will be carried out to determine the cost effectiveness of the intervention compared with standard care. DISCUSSION: The results of this pragmatic trial will provide evidence on the clinical and cost effectiveness of the intervention on lowering total cholesterol and addressing multiple cardiovascular disease risk factors in people with severe mental illnesses in GP Practices. TRIAL REGISTRATION: Current Controlled Trials ISRCTN13762819 . Date of Registration: 25 February 2013. Date and Version Number: 27 August 2014 Version 5

Comparison of kilometre and sub-kilometre scale simulations of a foehn wind event over the Larsen C Ice Shelf, Antarctic Peninsula using the Met Office Unified Model (MetUM)

A foehn event on 27 January 2011 over the Larsen C Ice Shelf (LCIS), Antarctic Peninsula and its interaction with an exisiting ground-based cold-air pool is simulated using the MetUM atmospheric model at kilometre and sub-kilometre scale grid spacing. Atmospheric model simulations at kilometre grid scales are an important tool for understanding the detailed circulation and temperature structure over the LCIS, especially the occurrence of foehn-induced surface melting, erosion of cold-air pools, and low-level wind jets (so-called foehn jets). But whether there is an improvement/convergence in the model representation of these features at sub-kilometre grid scales has yet to be established. The foehn event was simulated at grid spacings of 4, 1.5 and 0.5 km, with the results compared to automatic weather station and radiosonde measurements. The features commonly associated with foehn, such as a leeside hydraulic jump and enhanced leeside warming, were comparatively insensitive to resolution in the 4 to 0.5 km range, although the 0.5 km simulation shows a slightly sharper and larger hydraulic jump. By contrast, during the event the simulation of fine-scale foehn jets above the cold-air pool showed considerable dependence on grid spacing, although no evidence of convergence at higher resolution. During the foehn event, the MetUM model is characterised by a nocturnal cold bias of around 8 °C and an underestimate of the near-surface stability of the cold-air pool, neither of which improved with increased resolution. This finding identifies a key model limitation, at both kilometre and sub-kilometre scales, to realistically capture the vertical mixing in the boundary layer and its impact on thermodynamics, through either daytime heating from below or the downward penetration of foehn jet winds from above. Detailed model-resolved foehn jet dynamics thus plays a crucial role in controlling the near-surface temperature structure over the LCIS, as well as sub-grid turbulent mixing

Characteristics of surface “melt potential” over Antarctic ice shelves based on regional atmospheric model simulations of summer air temperature extremes from 1979/80 to 2018/19

We calculate a regional surface “melt potential” index (MPI) over Antarctic ice shelves that describes the frequency (MPI-freq, %) and intensity (MPI-int, K) of daily maximum summer temperatures exceeding a melt threshold of 273.15 K. This is used to determine which ice shelves are vulnerable to melt-induced hydrofracture and is calculated using near-surface temperature output for each summer from 1979/80 to 2018/19 from two high-resolution regional atmospheric model hindcasts (using the MetUM and HIRHAM5). MPI is highest for Antarctic Peninsula ice shelves (MPI-freq 23-35%, MPI-int 1.2-2.1 K), lowest (2-3%, < 0 K) for Ronne-Filchner and Ross ice shelves, and around 10-24% and 0.6-1.7 K for the other West and East Antarctic ice shelves. Hotspots of MPI are apparent over many ice shelves, and they also show a decreasing trend in MPI-freq. The regional circulation patterns associated with high MPI values over West and East Antarctic ice shelves are remarkably consistent for their respective region but tied to different large-scale climate forcings. The West Antarctic circulation resembles the central Pacific El Niño pattern with a stationary Rossby wave and a strong anticyclone over the high-latitude South Pacific. By contrast, the East Antarctic circulation comprises a zonally symmetric negative Southern Annular Mode pattern with a strong regional anticyclone on the plateau and enhanced coastal easterlies/weakened Southern Ocean westerlies. Values of MPI are 3-4 times larger for a lower temperature/melt threshold of 271.15 K used in a sensitivity test, as melting can occur at temperatures lower than 273.15 K depending on snowpack properties

Grey wolf genomic history reveals a dual ancestry of dogs

The grey wolf (Canis lupus) was the first species to give rise to a domestic population, and they remained widespread throughout the last Ice Age when many other large mammal species went extinct. Little is known, however, about the history and possible extinction of past wolf populations or when and where the wolf progenitors of the present-day dog lineage (Canisfamiliaris) lived(1-8). Here we analysed 72 ancient wolf genomes spanning the last 100,000 years from Europe, Siberia and North America. We found that wolf populations were highly connected throughout the Late Pleistocene, with levels of differentiation an order of magnitude lower than they are today. This population connectivity allowed us to detect natural selection across the time series, including rapid fixation of mutations in the gene IFT8840,000-30,000 years ago. We show that dogs are overall more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, suggesting a domestication process in the east. However, we also found that dogs in the Near East and Africa derive up to half of their ancestry from a distinct population related to modern southwest Eurasian wolves, reflecting either an independent domestication process or admixture from local wolves. None of the analysed ancient wolf genomes is a direct match for either of these dog ancestries, meaning that the exact progenitor populations remain to be located.Peer reviewe