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The sea level contribution of the Antarctic ice sheet constitutes a large uncertainty in future sea level projections. Here we apply a linear response theory approach to 16 state-of-the-art ice sheet models to estimate the Antarctic ice sheet contribution from basal ice shelf melting within the 21st century. The purpose of this computation is to estimate the uncertainty of Antarctica's future contribution to global sea level rise that arises from large uncertainty in the oceanic forcing and the associated ice shelf melting. Ice shelf melting is considered to be a major if not the largest perturbation of the ice sheet's flow into the ocean. However, by computing only the sea level contribution in response to ice shelf melting, our study is neglecting a number of processes such as surface-mass-balance-related contributions. In assuming linear response theory, we are able to capture complex temporal responses of the ice sheets, but we neglect any self-dampening or self-amplifying processes. This is particularly relevant in situations in which an instability is dominating the ice loss. The results obtained here are thus relevant, in particular wherever the ice loss is dominated by the forcing as opposed to an internal instability, for example in strong ocean warming scenarios. In order to allow for comparison the methodology was chosen to be exactly the same as in an earlier study (Levermann et al., 2014) but with 16 instead of 5 ice sheet models. We include uncertainty in the atmospheric warming response to carbon emissions (full range of CMIP5 climate model sensitivities), uncertainty in the oceanic transport to the Southern Ocean (obtained from the time-delayed and scaled oceanic subsurface warming in CMIP5 models in relation to the global mean surface warming), and the observed range of responses of basal ice shelf melting to oceanic warming outside the ice shelf cavity. This uncertainty in basal ice shelf melting is then convoluted with the linear response functions of each of the 16 ice sheet models to obtain the ice flow response to the individual global warming path. The model median for the observational period from 1992 to 2017 of the ice loss due to basal ice shelf melting is 10.2 mm, with a likely range between 5.2 and 21.3 mm. For the same period the Antarctic ice sheet lost mass equivalent to 7.4mm of global sea level rise, with a standard deviation of 3.7mm (Shepherd et al., 2018) including all processes, especially surface-mass-balance changes. For the unabated warming path, Representative Concentration Pathway 8.5 (RCP8.5), we obtain a median contribution of the Antarctic ice sheet to global mean sea level rise from basal ice shelf melting within the 21st century of 17 cm, with a likely range (66th percentile around the mean) between 9 and 36 cm and a very likely range (90th percentile around the mean) between 6 and 58 cm. For the RCP2.6 warming path, which will keep the global mean temperature below 2 °C of global warming and is thus consistent with the Paris Climate Agreement, the procedure yields a median of 13 cm of global mean sea level contribution. The likely range for the RCP2.6 scenario is between 7 and 24 cm, and the very likely range is between 4 and 37 cm. The structural uncertainties in the method do not allow for an interpretation of any higher uncertainty percentiles.We provide projections for the five Antarctic regions and for each model and each scenario separately. The rate of sea level contribution is highest under the RCP8.5 scenario. The maximum within the 21st century of the median value is 4 cm per decade, with a likely range between 2 and 9 cm per decade and a very likely range between 1 and 14 cm per decade.

Jonina Sigurgeirsdottir,1,2 Sigridur Halldorsdottir,3 Ragnheidur Harpa Arnardottir,3– 5 Gunnar Gudmundsson,1,6 Eythor Hreinn Bjornsson2 1Faculty of Medicine, University of Iceland, Reykjavik, Iceland; 2Pulmonary Department, Reykjalundur Rehabilitation Center, Mosfellsbaer, Iceland; 3Faculty of Graduate Studies, School of Health Sciences, University of Akureyri, Akureyri, Iceland; 4Department of Rehabilitation, Akureyri Hospital, Akureyri, Iceland; 5Department of Medical Sciences, Respiratory-, Allergy- and Sleep Research, Uppsala University, Uppsala, Sweden; 6Department of Respiratory Medicine and Sleep, Landspitali University Hospital, Reykjavik, IcelandCorrespondence: Jonina Sigurgeirsdottir, Pulmonary Department, Reykjalundur Rehabilitation Center, Furubyggd 28, Mosfellsbaer, 270, Iceland, Tel +354 6261740, Email jonina@reykjalundur.isAim: This phenomenological study was aimed at exploring principal physicians’ (participants’) experience of attending to COPD patients and motivating their self-management, in light of the GOLD clinical guidelines of COPD therapy.Methods: Interviews were conducted with nine physicians, who had referred patients to PR, five general practitioners (GPs) and four lung specialists (LSs). The interviews were recorded, transcribed, and analyzed through a process of deconstruction and reconstruction.Results: The participants experienced several ethical dilemmas in being principal physicians of COPD patients and motivating their self-management; primarily in the balancing act of adhering to the Hippocratic Oath of promoting health and saving lives, while respecting their patients’ choice regarding non-adherence eg, by still smoking. It was also a challenge to deal with COPD as a nicotine addiction disease, deal with patients’ denial regarding the harm of smoking and in motivating patient mastery of the disease. The participants used various strategies to motivate their patients’ self-management such as active patient education, enhancing the patients’ inner motivation, by means of an interdisciplinary approach, involving the patients’ significant other when appropriate, and by proposing PR.Conclusion: The findings indicate that being a principal physician of COPD patients and motivating their self-management is a balancing act, involving several dilemmas. Patients’ nicotine addiction and physicians’ ethical obligations are likely to create ethical dilemmas as the physician is obligated to respect the patients’ will, even though it contradicts what is best for the patient. The participants suggest strategies to motivate COPD patients’ self-management.Keywords: physicians, physician-patient relations, physician’s role, COPD, self-management, motivation, patient education, qualitative research, interviews

In recent decades, glaciers in the Amundsen Sea Embayment in West Antarctica have made the largest contribution to mass loss from the entire Antarctic Ice Sheet. Glacier retreat and acceleration have led to concerns about the stability of the region and the effects of future climate change. Coastal thinning and near-synchronous increases in ice flux across neighbouring glaciers suggest that ocean-driven melting is one of the main drivers of mass imbalance. However, the response of individual glaciers to changes in ocean conditions varies according to their local geometry. One of the largest and fastest-flowing of these glaciers, Pine Island Glacier (PIG), underwent a retreat from a subglacial ridge in the 1940s following a period of unusually warm conditions. Despite subsequent cooler periods, the glacier failed to recover back to the ridge and continued retreating to its present-day position. Here, we use the ice-flow model Úa to investigate the sensitivity of this retreat to changes in basal melting. We show that a short period of increased basal melt was sufficient to force the glacier from its stable position on the ridge and undergo an irreversible retreat to the next topographic high. Once high melting begins upstream of the ridge, only near-zero melt rates can stop the retreat, indicating a possible hysteresis in the system. Our results suggest that unstable and irreversible responses to warm anomalies are possible and can lead to substantial changes in ice flux over relatively short periods of only a few decades. [ABSTRACT FROM AUTHOR]

Knowledge of the ice thickness distribution of glaciers and ice caps is an important prerequisite for many glaciological and hydrological investigations. A wealth of approaches has recently been presented for inferring ice thickness from characteristics of the surface. With the Ice Thickness Models Intercomparison eXperiment (ITMIX) we performed the first coordinated assessment quantifying individual model performance. A set of 17 different models showed that individual ice thickness estimates can differ considerably - locally by a spread comparable to the observed thickness. Averaging the results of multiple models, however, significantly improved the results: on average over the 21 considered test cases, comparison against direct ice thickness measurements revealed deviations on the order of 10 ± 24% of the mean ice thickness (1σ estimate). Models relying on multiple data sets - such as surface ice velocity fields, surface mass balance, or rates of ice thickness change - showed high sensitivity to input data quality. Together with the requirement of being able to handle large regions in an automated fashion, the capacity of better accounting for uncertainties in the input data will be a key for an improved next generation of ice thickness estimation approaches.

Numerical modeling of ice sheet dynamics is a critical tool for projecting future sea level rise. Among all the processes responsible for the loss of mass of the ice sheets, enhanced ice discharge triggered by the retreat of marine-terminating glaciers is one of the key drivers. Numerical models of ice sheet flow are therefore required to include ice front migration in order to reproduce today's mass loss and to be able to predict their future. However, the discontinuous nature of calving poses a significant numerical challenge for accurately capturing the motion of the ice front. In this study, we explore different stabilization techniques combined with varying reinitialization strategies to enhance the numerical stability and accuracy of solving the level-set function, which tracks the position of the ice front. Through rigorous testing on an idealized domain with a semicircular and a straight-line ice front, including scenarios with diverse front velocities, we assess the performance of these techniques. The findings contribute to advancing our ability to model ice sheet dynamics, specifically calving processes, and provide valuable insights into the most effective strategies for simulating and tracking the motion of the ice front. [ABSTRACT FROM AUTHOR]

Coupled ice sheet-ocean models capable of simulating moving grounding lines are just becoming available. Such models have a broad range of potential applications in studying the dynamics of marine ice sheets and tidewater glaciers, from process studies to future projections of ice mass loss and sea level rise. The Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP) is a community effort aimed at designing and coordinating a series of model intercomparison projects (MIPs) for model evaluation in idealized setups, model verification based on observations, and future projections for key regions of the West Antarctic Ice Sheet (WAIS). Here we describe computational experiments constituting three interrelated MIPs for marine ice sheet models and regional ocean circulation models incorporating ice shelf cavities. These consist of ice sheet experiments under the Marine Ice Sheet MIP third phase (MISMIP+), ocean experiments under the Ice Shelf-Ocean MIP second phase (ISOMIP+) and coupled ice sheet-ocean experiments under the MISOMIP first phase (MISOMIP1). All three MIPs use a shared domain with idealized bedrock topography and forcing, allowing the coupled simulations (MISOMIP1) to be compared directly to the individual component simulations (MISMIP+ and ISOMIP+). The experiments, which have qualitative similarities to Pine Island Glacier Ice Shelf and the adjacent region of the Amundsen Sea, are designed to explore the effects of changes in ocean conditions, specifically the temperature at depth, on basal melting and ice dynamics. In future work, differences between model results will form the basis for the evaluation of the participating models.

Coupled ice sheet-ocean models capable of simulating moving grounding lines are just becoming available. Such models have a broad range of potential applications in studying the dynamics of marine ice sheets and tidewater glaciers, from process studies to future projections of ice mass loss and sea level rise. The Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP) is a community effort aimed at designing and coordinating a series of model intercomparison projects (MIPs) for model evaluation in idealized setups, model verification based on observations, and future projections for key regions of the West Antarctic Ice Sheet (WAIS). Here we describe computational experiments constituting three interrelated MIPs for marine ice sheet models and regional ocean circulation models incorporating ice shelf cavities. These consist of ice sheet experiments under the Marine Ice Sheet MIP third phase (MISMIP+), ocean experiments under the Ice Shelf-Ocean MIP second phase (ISOMIP+) and coupled ice sheet-ocean experiments under the MISOMIP first phase (MISOMIP1). All three MIPs use a shared domain with idealized bedrock topography and forcing, allowing the coupled simulations (MISOMIP1) to be compared directly to the individual component simulations (MISMIP+ and ISOMIP+). The experiments, which have qualitative similarities to Pine Island Glacier Ice Shelf and the adjacent region of the Amundsen Sea, are designed to explore the effects of changes in ocean conditions, specifically the temperature at depth, on basal melting and ice dynamics. In future work, differences between model results will form the basis for the evaluation of the participating models.

Jonina Sigurgeirsdottir,1,2 Sigridur Halldorsdottir,3 Ragnheidur Harpa Arnardottir,3– 5 Gunnar Gudmundsson,1,6 Eythor Hreinn Bjornsson2 1University of Iceland, Medical Faculty, Reykjavik, Iceland; 2Reykjalundur Rehabilitation Center, Lung Department, Mosfellsbaer, Iceland; 3University of Akureyri, School of Health Sciences, Faculty of Graduate Studies, Akureyri, Iceland; 4Akureyri Hospital, Department of Rehabilitation, Akureyri, Iceland; 5Uppsala University, Department of Medical Sciences, Respiratory-, Allergy- and Sleep Research, Uppsala, Sweden; 6Landspitali University Hospital, Department of Respiratory Medicine, Reykjavik, IcelandCorrespondence: Jonina SigurgeirsdottirReykjalundur Rehabilitation Center, Lung Department, Mosfellsbaer 270, IcelandTel +354 6261740Email jonina@reykjalundur.isAim: The aim of this phenomenological study was to explore principal family members’ experience of motivating patients with chronic obstructive pulmonary disease (COPD) towards self-management.Methods: Interviews were conducted with 10 family members (spouses and adult children) of COPD patients. The interviews were audio recorded, transcribed and analyzed thematically.Results: Being a principal family member of a COPD patient is characterized by frustrated caring; wanting the best for him/her and yet carrying a heavier burden than the person feels equipped for, lacking both knowledge about the disease progress and information about available healthcare resources. The situation demands much energy, due to COPD patients’ lack of stamina; family members’ fear of the patient’s possible breathlessness; willingness to help, though sometimes meeting with negative reactions from the patient; and feeling ignored by health professionals (HPs). Family members expressed a need for a formal connection between patient–family–HPs. The increasing burden experienced by patients’ family members is characterized by a sequential process in three phases of the patient’s declining self-management. In the early phase, family and patient are ignorant of COPD yet recognize the patient’s smoking as a risky lifestyle. In the intermediary phase, signs of COPD become evident to the family. The first turning point is when the family first observes the patient’s acute exacerbation. A second turning point is in the advanced phase, when family and patient recognize COPD as a progressive disease, possibly fatal. We also identified family members’ views on COPD patients’ needs, and their own roles, main frustrations and concerns.Conclusion: Family members’ experience of motivating COPD patients towards self-management is a sequential process where the family experiences advancing caring burden and declining self-management by the patient. We propose the establishment of COPD patients’ teams consisting of patient–family–HP, aimed at the patients’ best possible self-management.Keywords: chronic, obstructive, family’s needs, self-management, pulmonary rehabilitation, PR, qualitative research

The Greenland Ice Sheet contributed 10.6 mm to global sea level rise between 1992 and 2018, and it is projected to be the largest glacial contributor to sea level rise by 2100. Here we assess the relative importance of two major sources of uncertainty in 21st century ice loss projections: (1) the choice of sliding law and (2) the surface mass balance (SMB) forecast. Specifically, we used the ice flow model Úa to conduct an ensemble of runs for 48 combinations of sliding law and SMB forecast for three major Greenland outlet glaciers (Kangerlussuaq (KG), Humboldt (HU) and Petermann (PG) glaciers) with differing characteristics and evaluated how the sensitivity to these factors varied between the study glaciers. Overall, our results show that SMB forecasts were responsible for 4.45 mm of the variability in sea level rise by 2100 compared with 0.33 mm sea level equivalent (SLE) due to sliding law. HU had the largest absolute contribution to sea level rise and the largest range (2.16–7.96 mm SLE), followed by PG (0.84–5.42 mm SLE), and these glaciers showed similar patterns of ice loss across the SMB forecasts and sliding laws. KG had the lowest range and absolute values (- 0.60 to 3.45 mm SLE) of sea level rise, and the magnitude of mass loss by SMB forecast differed markedly between HU and PG. Our results highlight SMB forecasts as a key focus for improving estimates of Greenland's contribution to 21st century sea level rise. [ABSTRACT FROM AUTHOR]

Over the past decade, a wealth of research has been devoted to the detection of crevasses in glaciers and ice sheets via remote sensing and machine learning techniques. It is often argued that remotely sensed damage maps can function as early warning signals for shifts in ice shelf conditions from intact to damaged states and can serve as an important tool for ice sheet modellers to improve future sea level rise predictions. Here, we provide evidence for the Filchner–Ronne and Pine Island ice shelves that remotely sensed damage maps are only weakly related to the ice rate factor field A derived by an ice flow model when inverting for surface velocities. This technique is a common procedure in ice flow models, as it guarantees that any inferred changes in A relate to changes in ice flow measured through observations. The weak relationship found is improved when investigating heavily damaged shear margins, as observed on the Pine Island Ice Shelf; however, even in this setting, this association remains modest. Our findings suggest that many features identified as damage through remote sensing methods are not of direct relevance to present-day ice shelf flow. While damage can clearly play an important role in ice shelf processes and thus be relevant for ice sheet behaviour and sea level rise projections, our results imply that mapping ice damage directly from satellite observations may not directly help improve the representation of these processes in ice flow models. [ABSTRACT FROM AUTHOR]

The rate at which the Antarctic Ice Sheet loses mass is to a large degree controlled by ice-ocean interactions underneath small ice shelves, with the most sensitive regions concentrated in even smaller areas near grounding lines and local pinning points. Sufficient horizontal resolution is key to resolving critical ice-ocean processes in these regions, but difficult to afford in large-scale models used to predict the coupled response of the entire Antarctic Ice Sheet and the global ocean to climate change. In this study we describe the implementation of a framework that couples the ice sheet flow model Úa with the Finite Element Sea Ice Ocean Model (FESOM-1.4) in a configuration using depth-dependent vertical coordinates. The novelty of this approach is the use of horizontally unstructured grids in both model components, allowing us to resolve critical processes directly, while keeping computational demands within the range of feasibility. We use the Marine Ice Sheet–Ocean Model Intercomparison Project framework to verify that ice retreat and readvance is reliably simulated, and inaccuracies in mass, heat and salt conservation are small compared to the forcing signal. Further, we demonstrate the capabilities of our approach for a global ocean/Antarctic Ice Sheet domain. In a 39-year hindcast simulation (1979–2018) we resolve retreat behaviour of Pine Island Glacier, a known challenge for coarser resolution models. We conclude that Úa-FESOM is well suited to improve predictions of the Antarctic Ice Sheet evolution over centennial time scales. [ABSTRACT FROM AUTHOR]

Jonina Sigurgeirsdottir,1,2 Sigridur Halldorsdottir,3 Ragnheidur Harpa Arnardottir,3–5 Gunnar Gudmundsson,1,6 Eythor Hreinn Bjornsson21Faculty of Medicine, University of Iceland, Reykjavik, Iceland; 2Reykjalundur Rehabilitation Center, Mosfellsbaer, Iceland; 3School of Health Sciences, University of Akureyri, Akureyri, Iceland; 4Department of Rehabilitation, Akureyri Hospital, Akureyri, Iceland; 5Department of Medical Sciences, Respiratory-, Allergy-, and Sleep Research, Uppsala University, Uppsala, Sweden; 6Department of Respiratory Medicine, Landspitali University Hospital, Reykjavik, IcelandBackground: COPD is a common cause of morbidity and mortality. The aim of this study was to explore patients’ experiences, self-reported needs, and needs-driven strategies to cope with self-management of COPD.Patients and methods: In this phenomenological study, 10 participants with mild to severe COPD were interviewed 1–2 times, until data saturation was reached. In total, 15 in-depth interviews were conducted, recorded, transcribed, and analyzed.Results: COPD negatively affected participants’ physical and psychosocial well-being, their family relationships, and social life. They described their experiences of COPD like fighting a war without weapons in an ever-shrinking world with a loss of freedom at most levels, always fearing possible breathlessness. Fourteen needs were identified and eight clusters of needs-driven strategies that participants used to cope with self-management of COPD. Coping with the reality of COPD, a life-threatening disease, meant coping with dyspnea, feelings of suffocation, indescribable smoking addiction, anxiety, and lack of knowledge about the disease. Reduced participation in family and social life meant loss of ability to perform usual and treasured activities. Having a positive mindset, accepting help and assuming healthy lifestyle was important, as well as receiving continuous professional health care services. The participants’ needs-driven strategies comprised conducting financial arrangements, maintaining hope, and fighting their smoking addiction, seeking knowledge about COPD, thinking differently, facing the broken chain of health care, and struggling with accepting support. Procrastination and avoidance were also evident. Finally, the study also found that participants experienced a perpetuating cycle of dyspnea, anxiety, and fear of breathlessness due to COPD which could lead to more severe dyspnea and even panic attacks.Conclusion: COPD negatively affects patients’ physical and psychosocial well-being, family relationships and, social life. Identifying patients’ self-reported needs and needs-driven strategies can enable clinicians to empower patients by educating them to improve their self-management.Keywords: COPD, patients’ needs, self-management, pulmonary rehabilitation, qualitative research

Predictions of marine ice-sheet behaviour require models able to simulate grounding-line migration. We present results of an intercomparison experiment for plan-view marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no buttressing effects from lateral drag). Perturbation experiments specifying spatial variation in basal sliding parameters permitted the evolution of curved grounding lines, generating buttressing effects. The experiments showed regions of compression and extensional flow across the grounding line, thereby invalidating the boundary layer theory. Steady-state grounding-line positions were found to be dependent on the level of physical model approximation. Resolving grounding lines requires inclusion of membrane stresses, a sufficiently small grid size (

Over the past decade, a wealth of research has been devoted to the detection of crevasses in glaciers and ice sheets via remote sensing and machine learning techniques. It is often argued that remotely sensed damage maps can function as earlywarning signals for shifts in ice shelf conditions from intact to damaged states and can serve as an important tool for ice sheet modellers to improve future sea-level rise predictions. Here, we provide evidence for Filchner-Ronne and Pine Island ice shelves that remotely sensed damage maps are only weakly related to the ice rate factor field AA derived by an ice-flow model when inverting for surface velocities. This technique is a common procedure in ice flow models, as it guarantees that any inferred changes in AA relate to changes in ice flow measured through observations. The weak relationship found is improved when investigating heavily damaged shear margins, as observed on Pine Island Ice Shelf; yet, even in this setting, this association remains modest. Our findings suggest that many features identified as damage through remote sensing methods are not of direct relevance to present-day ice-shelf flow. While damage can clearly play an important role in iceshelf processes and thus be relevant for ice-sheet behaviour and sea-level rise projections, our results imply that mapping ice damage directly from satellite observations may not directly help improve the representation of these processes in ice-flow models. [ABSTRACT FROM AUTHOR]

Numerical modeling of ice sheet dynamics is a critical tool for projecting future sea-level rise. Among all the processes responsible for the loss of mass of the ice sheets, enhanced ice discharge triggered by the retreat of marine terminating glaciers is one of the key drivers. Numerical models of ice sheet flow are therefore required to include ice front migration in order to reproduce today's mass loss and be able to predict their future. However, the discontinuous nature of calving poses significant numerical challenge for accurately capturing the motion of the ice front. In this study, we explore different stabilization techniques combined with varying reinitialization strategies to enhance the numerical stability and accuracy of solving the level-set function, which tracks the position of the ice front. Through rigorous testing on an idealized domain with semicircular and a straight-line ice front, including scenarios with diverse front velocities, we assess the performance of these techniques. The findings contribute to advancing our ability to model ice sheet dynamics, specifically calving processes, and provide valuable insights into the most effective strategies for simulating and tracking the motion of the ice front. [ABSTRACT FROM AUTHOR]