An idealised wave-ice interaction model without subgrid spatial and temporal discretisations

A modified version of the wave-ice interaction model proposed by Williams et al (2013a,b) is presented for an idealised transect geometry. Wave attenuation due to ice floes and wave-induced ice fracture are both included in the wave-ice interaction model. Subgrid spatial and temporal discretisations are not required in the modified version of the model, thereby facilitating its future integration into large-scaled coupled models. Results produced by the new model are compared to results produced by the original model of Williams et al (2013b).Comment: 8 pages, 3 figure

Antarctic Sea Ice Area in CMIP6

Fully coupled climate models have long shown a wide range of Antarctic sea ice states and evolution over the satellite era. Here, we present a high‐level evaluation of Antarctic sea ice in 40 models from the most recent phase of the Coupled Model Intercomparison Project (CMIP6). Many models capture key characteristics of the mean seasonal cycle of sea ice area (SIA), but some simulate implausible historical mean states compared to satellite observations, leading to large intermodel spread. Summer SIA is consistently biased low across the ensemble. Compared to the previous model generation (CMIP5), the intermodel spread in winter and summer SIA has reduced, and the regional distribution of sea ice concentration has improved. Over 1979–2018, many models simulate strong negative trends in SIA concurrently with stronger‐than‐observed trends in global mean surface temperature (GMST). By the end of the 21st century, models project clear differences in sea ice between forcing scenarios

Developing an institutional framework for supporting supervisors of research students: A practical guide

This booklet describes the outcomes of a unique interinstitutional project undertaken in Ireland between 2008 and 2012 to develop a common framework for the support of supervisors of postgraduate research students. The experiences of the seven institutions who ultimately participated in the project are summarized in the form of a series of commentaries on approaches to such training, and a description of the primary elements of the final framework itself. It is intended that this information may be of use to any institutions interested in developing their own supports for research supervisors, and ultimately will be of benefit to the supervisors themselves and, of course, their students

Ocean fronts formed at sea ice boundaries

Meltwater input from sea ice forms a buoyancy source for the upper ocean which creates a strong density gradient in both horizontal and vertical directions. If, in particular, the ocean density front is formed in the Bering sea during winter, the frontal dynamics are influenced by local shelf/slope processes. further, ice is advected across the front by the wind, thereby altering the heat flux to the ice and leading to an increase in the freshwater buoyancy flux to the ocean. Hence, th~ surface manifestation of the front is governed by ice position. In this thesis a detailed study of ice and ocean parameters in such a system is presented using data from the 1982-3 winter Season in the Bering sea. Particular attention is given to the results from MIZEX-West (1983), an intensive mid-winter study. Modelling of the physical processes involved in the development of the meltwater front follows two directions; firstly the buoyancy input to small scale fronts formed in the summer marginal ice zone is considered and secondly, an hierarchy of numerical models of ice and ocean dynamics are employed. Results are also reported of fieldwork carried out in the East Greenland current (MIZEX-84, LANCE cruise) using a novel, medium resolution, portable CTD system to measure upper ocean density gradients from floe edges and small boats. However, during these experiments conditions were not ideal for the development of meltwater fronts analogous to those found in the Bering Sea. Additionally, one-dimensional and two-layer quasi-steady ocean models coupled to an ice cover are discussed. These models proved useful tools in our understanding of the air-ice-ocean exchanges and frontal adjustment processes within the more complex system. More detailed modelling studies were undertaken using a two-dimensional, coupled ice-ocean model focusing on the interactive thermodynamic forcing during ice ablation and ice accretion. The thermal and salinity fluxes in the coupling were related to the ice growth calculated by a thermodynamic ice model similar to those is employed by larger scale climate studies. Hence, over short time scales the ice growth in leads and open water that may occur after a change in external forcing conditions is not well represented. The functional form of the internal stress in the ice momentum equation is investigated with the model. When the amplitude of the internal stress decreases by several orders of magnitude in a few grid points the model was unable to sustain such a gradient and was liable to generate numerical instabilities. If however, the near discontinuity in the internal stress at the ice edge is treated like a moving shock wave (after Roed and O'Brien, 1983) then the ice compactness maintains a coherent ice edge under conditions simulating the passage of a storm

Comparison of warming trends predicted over the next century around Antarctica from two coupled models

This paper investigates the climate change in two atmosphere-ice-ocean coupled climate models - the UKMO and the CSIRO - in the Antarctic region over the next century. The objectives were to see if an enhanced level of greenhouse-gas forcing results in a surface temperature signal above background variability, and to see if this pattern of change resembles the change seen to date in Antarctica, especially the warming around the Peninsula. The models show that although reduced sea-ice compactness is responsible for regions of enhanced air-temperature anomalies, these ice-compactness anomalies are determined by different mechanisms in the respective models. The pattern of warming in both models does not match the differential rates of warming seen in the observations of temperature change over the Antarctic continent in the last few decades. Also the level of background ocean variability in the Drake Passage and Weddell Sea region hampers the clear definition of a signal over the Antarctic Peninsula in the coupled models. Although no winter enhancement in warming over the Peninsula region is found, an autumn anomaly is seen in one of the models. The mechanism for this feature is documented, and an explanation of why it does not persist throughout the winter season is presented