Modeling of the northern hemisphere ice sheets during the last glacial cycle and glaciological sensitivity

We present a new three-dimensional thermomechanically coupled ice sheet model of the northern hemisphere to reconstruct the Quaternary ice sheets during the last glacial cycle. The model includes basal sliding, internal representations of the surface mass balance, glacial isostasy, and a treatment for marine calving. The time dependent forcing consists of temperature and precipitation anomalies from the UKMO GCM scaled to the GRIP ice core ∂18O record. Model parameters were chosen to best match geomorphological inferences on maximum LGM extent and global eustatic sea level change. For our standard run we find a maximum ice volume of 57 x 106 km3 at 18.5 ka cal BP. This corresponds to a eustatic sea level lowering of 110 m after correction for hydro-isostatic displacement and anomalous ice resulting from defects in the PMIP climatic forcing. Of this 110 m, 82 m was stored in the North American ice sheet and 25 m in the Eurasian ice sheet. We determine the qualitative and quantitative response of the model from a comprehensive sensitivity study in which the most important parameters were varied over their respective ranges of uncertainty. Model outputs comparable to the observational record were explored in detail as a linear function along the axes of parameter space of the reference model. The method reveals the dominance of climate uncertainty when modelling the LGM configuration of the northern hemisphere ice sheets, but also highlights the role of ice rheology and basal processes for aspect ratio, and glacial isostasy and calving for the timing of maximum ice volume

All-optical flip-flops using electrically pumped microdisk lasers integrated on silicon

We demonstrate flip-flop operation using the directional bistability in ultra-small microdisks (7.5 mu m diameter) heterogeneously bonded on a silicon chip. The pulse energies are only 1.8 fJ and the bias current is 3.5 mA

3D numerical simulation of ship resistance in restricted waterways including ship squat effects

This study focuses on the effect of waterway restriction on ship resistance of an inland vessel. A 3D numerical model allowing to predict ship resistance in confined waters by taking ship sinkage into account has been developed. The numerical results are compared to experimental data from towing tank test and the influence of taking ship sinkage into account on the prediction error is studied

Increased Runoff from Melt from the Greenland Ice Sheet: A Response to Global Warming

The authors attribute significantly increased Greenland summer warmth and Greenland Ice Sheet melt and runoff since 1990 to global warming. Southern Greenland coastal and Northern Hemisphere summer temperatures were uncorrelated between the 1960s and early 1990s but were significantly positively correlated thereafter. This relationship appears to have been modulated by the North Atlantic Oscillation, whose summer index was significantly (negatively) correlated with southern Greenland summer temperatures until the early 1990s but not thereafter. Significant warming in southern Greenland since �1990, as also evidenced from Swiss Camp on the west flank of the ice sheet, therefore reflects general Northern Hemisphere and global warming. Summer 2003 was the warmest since at least 1958 in coastal southern Greenland. The second warmest coastal summer 2005 had the most extensive anomalously warm conditions over the ablation zone of the ice sheet, which caused a record melt extent. The year 2006 was the third warmest in coastal southern Greenland and had the third-highest modeled runoff in the last 49 yr from the ice sheet; five of the nine highest runoff years occurred since 2001 inclusive. Significantly rising runoff since 1958 was largely compensated by increased precipitation and snow accumulation. Also, as observed since 1987 in a single composite record at Summit, summer temperatures near the top of the ice sheet have declined slightly but not significantly, suggesting the overall ice sheet is experiencing a dichotomous response to the recent general warming: possible reasons include the ice sheet's high thermal inertia, higher atmospheric cooling, or changes in regional wind, cloud, and/or radiation patterns. © 2008 American Meteorological Society

High resolution (1 km) positive degree-day modelling of Greenland ice sheet surface mass balance, 1870–2012 using reanalysis data

We show results from a positive degree-day (PDD) model of Greenland ice sheet (GrIS) surface mass balance (SMB), 1870–2012, forced with reanalysis data. The model includes an improved daily temperature parameterization as compared with a previous version and is run at 1 km rather than 5 km resolution. The improvements lead overall to higher SMB with the same forcing data. We also compare our model with results from two regional climate models (RCMs). While there is good qualitative agreement between our PDD model and the RCMs, it usually results in lower precipitation and lower runoff but approximately equivalent SMB: mean 1979–2012 SMB (± standard deviation), in Gt a−1, is 382 ± 78 in the PDD model, compared with 379 ± 101 and 425 ± 90 for the RCMs. Comparison with in situ SMB observations suggests that the RCMs may be more accurate than PDD at local level, in some areas, although the latter generally compares well. Dividing the GrIS into seven drainage basins we show that SMB has decreased sharply in all regions since 2000. Finally we show correlation between runoff close to two calving glaciers and either calving front retreat or calving flux, this being most noticeable from the mid-1990s

[I] Why do we find so many meteorites on the Nansen blue ice field and where else could we look?

The Tenth Symposium on Polar Science/Special session: [S] Future plan of Antarctic research: Towards phase X of the Japanese Antarctic Research Project (2022-2028) and beyond, Tue. 3 Dec. / 2F Auditorium, National Institute of Polar Researc