Table 1: Discharge, mass flux, maximum velocity and ice thickness of glaciers from Dronning Maud Land, Antarctica

Mass transport and mass flux values for the different types of glaciers in the Sør-Rondane are calculated from computer models, based upon gravity data and geodetic stake velocity measurements. The results are interpreted in the light of a general flow line analysis, glacial geological investigations and of the ablation terms of the mass balance for Dronning Maud Land and Antarctica.

Occurence and thickness of flood layers in varved sediments of Lake Ammersee

Microfacies analyses and X-ray fluorescence scanning (µ-XRF) at sub-mm resolution were conducted on the varved Mid- to Late Holocene interval of two sediment profiles from pre-alpine Lake Ammersee (southern Germany). The coring sites are located in a proximal (AS10prox) and distal (AS10dist) position towards the main tributary River Ammer, in 1.8 km distance from each other. To shed light on sediment distribution within the lake, particular emphasis was (1) the detection of intercalated detrital layers and their micro-sedimentological features, and (2) intra-basin correlation of these event deposits. Detrital layers were dated by microscopic varve counting, verified by accelerator mass spectrometry 14C dating of terrestrial plant macrofossils. Since ~5500 varve years (vyr) BP, in total 1573 detrital layers were detected in either one or both of the investigated sediment profiles. Based on their microfacies, geochemistry, and proximal-distal deposition pattern, detrital layers were interpreted as River Ammer flood deposits. Earlier studies on flood layer seasonality have proven that flood layer deposition occurs predominantly during spring and summer, the flood season at Lake Ammersee. Most prominent features of the record are the onset of regular flood layer deposition at ~5500 vyr BP in AS10prox and ~ 2800 vyr BP in AS10dist as well as three major increases in mean flood layer thickness at ~5500, 2800, and 400 vyr BP. Integrating information from both sediment profiles allowed to interpret these changes in terms of shifts towards higher mean flood intensity. Proposed triggering mechanisms are gradual reduction in Northern Hemisphere orbital summer forcing and superimposed centennial-scale solar activity minima. Likely responses to this forcing are enhanced equator-to-pole temperature gradients and changes in synoptic-scale atmospheric circulation. The consequences for the Ammersee region are more intense cyclones leading to extremer rainfall and flood events in spring and summer.

Lithospheric thickness of Pangea

Surface wave tomography, using the fundamental Rayleigh wave velocities and those of higher modes between 1 and 4 and periods between 50 and 160 s, is used to image structures with a horizontal resolution of ~250 km and a vertical resolution of ~50 km to depths of ~300 km in the mantle. A new model, PM_v2_2012, obtained from 3×10**6 seismograms, agrees well with earlier lower resolution models. It is combined with temperature estimates from oceanic plate models and with pressure and temperature estimates from the mineral compositions of garnet peridotite nodules to generate a number of estimates of SV(P,T) based on geophysical and petrological observations alone. These are then used to estimate the unrelaxed shear modulus and its derivatives with respect to pressure and temperature, which agree reasonably with values from laboratory experiments. At high temperatures relaxation occurs, causing the shear wave velocity to depend on frequency. This behaviour is parameterised using a viscosity to obtain a Maxwell relaxation time. The relaxation behaviour is described using a dimensionless frequency, which depends on an activation energy E and volume Va. The values of E and Va obtained from the geophysical models agree with those from laboratory experiments on high temperature creep. The resulting expressions are then used to determine the lithospheric thickness from the shear wave velocity variations. The resolution is improved by about a factor of two with respect to earlier models, and clearly resolves the thick lithosphere beneath active intracontinental belts that are now being shortened. The same expressions allow the three dimensional variations of the shear wave attenuation and viscosity to be estimated.