Seabed corrugations beneath an Antarctic ice shelf revealed by autonomous underwater vehicle survey: Origin and implications for the history of Pine Island Glacier

Ice shelves are critical features in the debate about West Antarctic ice sheet change and sea level rise, both because they limit ice discharge and because they are sensitive to change in the surrounding ocean. The Pine Island Glacier ice shelf has been thinning rapidly since at least the early 1990s, which has caused its trunk to accelerate and retreat. Although the ice shelf front has remained stable for the past six decades, past periods of ice shelf collapse have been inferred from relict seabed "corrugations" (corrugated ridges), preserved 340 km from the glacier in Pine Island Trough. Here we present high-resolution bathymetry gathered by an autonomous underwater vehicle operating beneath an Antarctic ice shelf, which provides evidence of long-term change in Pine Island Glacier. Corrugations and ploughmarks on a sub-ice shelf ridge that was a former grounding line closely resemble those observed offshore, interpreted previously as the result of iceberg grounding. The same interpretation here would indicate a significantly reduced ice shelf extent within the last 11 kyr, implying Holocene glacier retreat beyond present limits, or a past tidewater glacier regime different from today. The alternative, that corrugations were not formed in open water, would question ice shelf collapse events interpreted from the geological record, revealing detail of another bed-shaping process occurring at glacier margins. We assess hypotheses for corrugation formation and suggest periodic grounding of ice shelf keels during glacier unpinning as a viable origin. This interpretation requires neither loss of the ice shelf nor glacier retreat and is consistent with a "stable" grounding-line configuration throughout the Holocene

What have we learnt from palaeoclimate simulations?

There has been a gradual evolution in the way that palaeoclimate modelling and palaeoenvironmental data are used together to understand how the Earth System works, from an initial and largely descriptive phase through explicit hypothesis testing to diagnosis of underlying mechanisms. Analyses of past climate states are now regarded as integral to the evaluation of climate models, and have become part of the toolkit used to assess the likely realism of future projections. Palaeoclimate assessment has demonstrated that changes in large-scale features of climate that are governed by the energy and water balance show consistent responses to changes in forcing in different climate states, and these consistent responses are reproduced by climate models. However, state-of-the-art models are still largely unable to reproduce observed changes in climate at a regional scale reliably. While palaeoclimate analyses of state-of-the-art climate models suggest an urgent need for model improvement, much work is also needed on extending and improving palaeoclimate reconstructions and quantifying and reducing both numerical and interpretative uncertainties

Past Arctic aliens have passed away, current ones may stay

Published version. Source at http://doi.org/10.1007/s10530-015-0937-9.Increased human activity and climate change are expected to increase the numbers and impact of alien species in the Arctic, but knowledge of alien species is poor in most Arctic regions. Through field investigations over the last 10 years, and review of alien vascular plant records for the high Arctic Archipelago Svalbard over the past 130 years, we explored long term trends in persistence and phenology. In total, 448 observations of 105 taxa have been recorded from 28 sites. Recent surveys at 18 of these sites revealed that alien species had disappeared at half of them. Investigations at a further 49 sites characterised by former human activity and/or current tourist landing sites did not reveal any alien species. Patterns of alien species distribution suggest that greater alien species richness is more likely to be aligned with ongoing human inhabitation than sites of transient use. The probability of an alien species being in a more advanced phenological stage increased with higher mean July temperatures. As higher mean July temperatures are positively correlated with more recent year, the latter finding suggests a clear warming effect on the increased reproductive potential of alien plants, and thus an increased potential for spread in Svalbard. Given that both human activity and temperatures are expected to increase in the future, there is need to respond in policy and action to reduce the potential for further alien species introduction and spread in the Arctic

Outcome following anaesthesia in infancy in the Nordic countries : Subgroup analysis of the NECTARINE study

Introduction: The neonate and children audit of anaesthesia practice in Europe (NECTARINE) prospective observational study reported an incidence of 35.2% of critical events requiring intervention during 6542 anaesthetics in 5609 infants up to 60 weeks postmenstrual age (PMA) from 165 centres in 31 European countries. Methods: Sub-analysis of the cohort from the Nordic countries (8% of the entire cohort) was conducted. Secondary aims were to describe the Nordic countries' anaesthetic practices and compare morbidity and mortality with the overall European cohort. Results: Eleven Nordic centres recruited 447 infants (66% males, 37.3% born preterm and 45% had congenital anomalies) undergoing anaesthesia for 530 surgical or non-surgical procedures at 25–60 weeks PMA. Perioperative critical events triggered interventions in 228/530 (43%) cases. Hypotension (12.6%) or hypoxaemia (11.7%) were more common in younger patients and those with co-morbidities. Hypo/hypercapnia occurred in 1.5%/4.7% of cases. More than two attempts for intubation were required in 13 (2.9%) infants (max three attempts). Distribution of ASA-Physical Status Scores was similar to the total European cohort (40% was ASA > 2). A total of 236/530 (44.5%) patients were admitted to the postoperative intensive care unit. Thirty-day morbidity (complications in 87/447 = 19.5%) and mortality (8/447, 1.8%) did not differ from the overall European cohort. Hospital re-admissions were significant up to 90 days (98/447 = 21.9%). Conclusions: In Nordic countries, anaesthesia in young infant children is resource-demanding, and perioperative critical events and co-morbidities are common. Thirty-day morbidity and mortality data in the Nordic countries did not differ from the overall European cohort.publishedVersionPeer reviewe

On the Reconstruction of Palaeo-Ice Sheets: Recent Advances and Future Challenges

Reconstructing the growth and decay of palaeo-ice sheets is critical to understanding mechanisms of global climate change and associated sea-level fluctuations in the past, present and future. The significance of palaeo-ice sheets is further underlined by the broad range of disciplines concerned with reconstructing their behaviour, many of which have undergone a rapid expansion since the 1980s. In particular, there has been a major increase in the size and qualitative diversity of empirical data used to reconstruct and date ice sheets, and major improvements in our ability to simulate their dynamics in numerical ice sheet models. These developments have made it increasingly necessary to forge interdisciplinary links between sub-disciplines and to link numerical modelling with observations and dating of proxy records. The aim of this paper is to evaluate recent developments in the methods used to reconstruct ice sheets and outline some key challenges that remain, with an emphasis on how future work might integrate terrestrial and marine evidence together with numerical modelling. Our focus is on pan-ice sheet reconstructions of the last deglaciation, but regional case studies are used to illustrate methodological achievements, challenges and opportunities. Whilst various disciplines have made important progress in our understanding of ice-sheet dynamics, it is clear that data-model integration remains under-used, and that uncertainties remain poorly quantified in both empirically-based and numerical ice-sheet reconstructions. The representation of past climate will continue to be the largest source of uncertainty for numerical modelling. As such, palaeo-observations are critical to constrain and validate modelling. State-of-the-art numerical models will continue to improve both in model resolution and in the breadth of inclusion of relevant processes, thereby enabling more accurate and more direct comparison with the increasing range of palaeo-observations. Thus, the capability is developing to use all relevant palaeo-records to more strongly constrain deglacial (and to a lesser extent pre-LGM) ice sheet evolution. In working towards that goal, the accurate representation of uncertainties is required for both constraint data and model outputs. Close cooperation between modelling and data-gathering communities is essential to ensure this capability is realised and continues to progress

Underway surface water data during the Tara Oceans expedition in 2013

The Tara Oceans Expedition (2009-2013) sampled the world oceans on board a 36 m long schooner, collecting environmental data and organisms from viruses to planktonic metazoans for later analyses using modern sequencing and state-of-the-art imaging technologies. Tara Oceans Data are particularly suited to study the genetic, morphological and functional diversity of plankton. During the entire expedition (2009-2013), underway measurements were obtained from a meteorological station (BATOS), a thermosalinograph (TSG, SBE 45), a Fast Repetition Rate Flurometer (FRRF, LIFT-FRR01), and a spectrophotometer (WETLabs AC-S). In 2013 underway measurements were enhanced by adding a Photosynthetically Available Radiation (PAR) sensor (QCP2350, Biospherical Instruments, Inc.), a laser spectrofluorometer (WETLabs ALFA, Chekalyuk et al., 2012) that replaced the FRRF, a spectral backscattering sensor (WETLabs Eco-bb3), a pCO2 sensor (ProOceanus CO2-Pro), a pH sensor (Satlantic, SeaFET) and a particle imaging system triggered by chlorophyll-a fluorescence (a prototype of McLane Research Laboratories' Imaging FlowCytobot, Sosik Lab, WHOI). Discrete measurements of CDOM absorption measurements were made using an Ultrapath (WPI Inc.) to calibrate the in-line AC-S. Hence the AC-S was also used to provide CDOM absorption in addition to particulate matter properties. The present dataset contains surface water data measured during the 2013 campaigns of the Tara Oceans Expedition. Latitude and Longitude were obtained from TSG data. The time stamp of this data set is harmonised with that of other underway data in this collection