The impact of a seasonally ice free Arctic Ocean on the temperature, precipitation and surface mass balance of Svalbard

The observed decline in summer sea ice extent since the 1970s is predicted to continue until the Arctic Ocean is seasonally ice free during the 21st Century. This will lead to a much perturbed Arctic climate with large changes in ocean surface energy flux. Svalbard, located on the present day sea ice edge, contains many low lying ice caps and glaciers and is expected to experience rapid warming over the 21st Century. The total sea level rise if all the land ice on Svalbard were to melt completely is 0.02 m. The purpose of this study is to quantify the impact of climate change on Svalbard’s surface mass balance (SMB) and to determine, in particular, what proportion of the projected changes in precipitation and SMB are a result of changes to the Arctic sea ice cover. To investigate this a regional climate model was forced with monthly mean climatologies of sea surface temperature (SST) and sea ice concentration for the periods 1961–1990 and 2061–2090 under two emission scenarios. In a novel forcing experiment, 20th Century SSTs and 21st Century sea ice were used to force one simulation to investigate the role of sea ice forcing. This experiment results in a 3.5 m water equivalent increase in Svalbard’s SMB compared to the present day. This is because over 50 % of the projected increase in winter precipitation over Svalbard under the A1B emissions scenario is due to an increase in lower atmosphere moisture content associated with evaporation from the ice free ocean. These results indicate that increases in precipitation due to sea ice decline may act to moderate mass loss from Svalbard’s glaciers due to future Arctic warming

A commentary on “how to interpret expert judgment assessments of twenty-first century sea-level rise” by Hylke de Vries and Roderik SW van de Wal

We clarify key aspects of the evaluation, by de Vries and van de Wal (2015), of our expert elicitation paper on the contributions of ice sheet melting to sea level rise due to future global temperature rise scenarios (Bamber and Aspinall 2013), and extend the conversation with further analysis of their proposed approach for combining expert uncertainty judgments.Applied Probabilit

Recent large increases in freshwater fluxes from Greenland into the North Atlantic

[1] Freshwater (FW) fluxes from river runoff and precipitation minus evaporation for the pan Arctic seas are relatively well documented and prescribed in ocean GCMs. Fluxes from Greenland on the other hand are generally ignored altogether, despite their potential impacts on ocean circulation and marine biology. Here, we present a reconstruction of the spatially distributed FW flux from Greenland for 1958–2010. We find a modest increase into the Arctic Ocean during this period. Fluxes into the Irminger Basin, however, have increased by fifty percent (6.3 ± 0.5 km3 yr−2) in less than twenty years. This greatly exceeds previous estimates. For the ice sheet as a whole the rate of increase since 1992 is 16.9 ± 1.8 km3 yr−2. The cumulative FW anomaly since 1995 is 3200 ± 358 km3, which is about a third of the magnitude of the Great Salinity Anomaly (GSA) of the 1970s. If this trend continues into the future, the anomaly will exceed that of the GSA by about 2025

Complex evolving patterns of mass loss from Antarctica’s largest glacier

Pine Island Glacier has contributed more to sea level rise over the past four decades than any other glacier in Antarctica. Model projections indicate that this will continue in the future but at conflicting rates. Some models suggest that mass loss could dramatically increase over the next few decades, resulting in a rapidly growing contribution to sea level and fast retreat of the grounding line, where the grounded ice meets the ocean. Other models indicate more moderate losses. Resolving this contrasting behaviour is important for sea level rise projections. Here, we use high-resolution satellite observations of elevation change since 2010 to show that thinning rates are now highest along the slow-flow margins of the glacier and that the present-day amplitude and pattern of elevation change is inconsistent with fast grounding-line migration and the associated rapid increase in mass loss over the next few decades. Instead, our results support model simulations that imply only modest changes in grounding-line location over that timescale. We demonstrate how the pattern of thinning is evolving in complex ways both in space and time and how rates in the fast-flowing central trunk have decreased by about a factor five since 2007

Establishing Professionalism through Digital Health Platforms

Despite the emerging interest in (health) platforms, there is limited research on their role in shaping professional work. Existing research has primarily focused on how platforms generate new forms of work, such as micro-tasking and crowdworking. There is limited understanding, however, about what forms professional work might take place on platforms, and, perhaps more importantly, how platforms can establish professionalism, primarily in contexts where this is under-developed or -valued. Our paper illustrates how this can be achieved drawing on a longitudinal qualitative study of a non-profit platform that is dedicated to delivering free online health education in post-conflict countries. The paper discusses four mechanisms through which platforms make up professionals: standardisation of clinical practice; normalisation of professional behaviour; development of medical knowledge; and inculcation of values. It then aims to discuss the paradoxical bureaucratic effects platforms may have as they enable those mechanisms and the potential colonising consequences they may engender

Radio Echo Sounding Studies of Svalbard Glaciers

The objective of this study was to investigate the radio echo sounding properties of Svalbard glaciers and to use these data to obtain information about the glaciological environment. Particular emphasis was placed on obtaining an understanding of the dielectric properties of the ice and reflecting boundaries present. These were then used to elucidate the physical processes causing them. First, a theoretical model, describing the dielectric properties of a wet bed, was developed. The ice/bed interface was then investigated using, as the primary data source, radar reflection coefficients. From these data inferences about the presence of water and/or debris, roughness of the interface and geographical trends were made. A number of geological divides were detected. Second, the dielectric properties of Svalbard ice were considered using i) radio echo sounding data on the bulk in situ radar absorption and ii) measurements made on the dielectric properties of a sample of Spitsbergen ice. Data were collected between 20 Hz and 100 kHz in the temperature range -2.5 to -44.0C . From these and other data deductions about the thermal regime of the ice masses were made and a geographical trend, linked to the reflection coefficients, observed. The theory of dielectric absorption in ice was discussed with an emphasis on the high frequency, radio echo sounding characteristics. Third, the properties of an extraordinary internal reflecting horizon ( observed on 60% of the glaciers sounded in 1983) were investigated. A model was developed to describe the scattering properties of inhomogeneities ( of arbitrary size) within ice. Using this, and data on the re:flec~ing properties of the horizons, they were attributed to the presence of a finite quantity of water. The implications of this finding were considered. Finally, the surface and, where available, bedrock profiles of 40 glaciers and six ice caps, in Spitsbergen, were presente

Attributing decadal climate variability in coastal sea-level trends

Decadal sea-level variability masks longer-term changes due to natural and anthropogenic drivers in short-duration records and increases uncertainty in trend and acceleration estimates. When making regional coastal management and adaptation decisions, it is important to understand the drivers of these changes to account for periods of reduced or enhanced sea-level change. The variance in decadal sea-level trends about the global mean is quantified and mapped around the global coastlines of the Atlantic, Pacific, and Indian oceans from historical CMIP6 runs and a high-resolution ocean model forced by reanalysis data. We reconstruct coastal, sea-level trends via linear relationships with climate mode and oceanographic indices. Using this approach, more than one-third of the variability in decadal sea-level trends can be explained by climate indices at 24.6 % to 73.1 % of grid cells located within 25 km of a coast in the Atlantic, Pacific, and Indian oceans. At 10.9 % of the world's coastline, climate variability explains over two-thirds of the decadal sea-level trend. By investigating the steric, manometric, and gravitational components of sea-level trend independently, it is apparent that much of the coastal ocean variability is dominated by the manometric signal, the consequence of the open-ocean steric signal propagating onto the continental shelf. Additionally, decadal variability in the gravitational, rotational, and solid-Earth deformation (GRD) signal should not be ignored in the total. There are locations such as the Persian Gulf and African west coast where decadal sea-level variability is historically small that are susceptible to future changes in hydrology and/or ice mass changes that drive intensified regional GRD sea-level change above the global mean. The magnitude of variance explainable by climate modes quantified in this study indicates an enhanced uncertainty in projections of short- to mid-term regional sea-level trend

The instantaneous impact of calving and thinning on the Larsen C Ice Shelf

The Antarctic Peninsula has seen rapid and widespread changes in the extent of its ice shelves in recent decades, including the collapse of the Larsen A and B ice shelves in 1995 and 2002, respectively. In 2017 the Larsen C Ice Shelf (LCIS) lost around 10 % of its area by calving one of the largest icebergs ever recorded (A68). This has raised questions about the structural integrity of the shelf and the impact of any changes in its extent on the flow of its tributary glaciers. In this work, we used an ice flow model to study the instantaneous impact of changes in the thickness and extent of the LCIS on ice dynamics and in particular on changes in the grounding line flux (GLF). We initialised the model to a pre-A68 calving state and first replicated the calving of the A68 iceberg. We found that there was a limited instantaneous impact on upstream flow – with speeds increasing by less than 10 % across almost all of the shelf – and a 0.28 % increase in GLF. This result is supported by observations of ice velocity made before and after the calving event. We then perturbed the ice-shelf geometry through a series of instantaneous, idealised calving and thinning experiments of increasing magnitude. We found that significant changes to the geometry of the ice shelf, through both calving and thinning, resulted in limited instantaneous changes in GLF. For example, to produce a doubling of GLF from calving, the new calving front needed to be moved to 5 km from the grounding line, removing almost the entire ice shelf. For thinning, over 200 m of the ice-shelf thickness had to be removed across the whole shelf to produce a doubling of GLF. Calculating the instantaneous increase in GLF (607 %) after removing the entire ice shelf allowed us to quantify the total amount of buttressing provided by the LCIS. From this, we identified that the region of the ice shelf in the first 5 km downstream of the grounding line provided over 80 % of the buttressing capacity of the shelf. This is due to the large resistive stresses generated in the narrow, local embayments downstream of the largest tributary glaciers