Is the coarse-grid Global Climate Model a useful tool for regional paleoclimate reconstruction?

This study considers the climate at the time of the Weichselian ice sheet maximum in Central Europe, especially in Poland, in respect of the NASA Educational version of Global Climate Model (EdGCM). The final results of the EdGCM simulations for the Last Glacial Maximum (LGM) are presented here and these have been analysed to determine whether or not they are useful for regional scale modelling; the problem being that, in a global climate model, both horizontal and vertical grid resolution is very low. Also, an attempt has been made to define the role of the ice megalobe which, in terms of the numerical coarse-grid model,covered the northern parts of Germany and Poland. The broad details of the climate during the Weichselian are defined and our results are compared with previous opinion. The influence of ice megalobe on regional climate is demonstrated and it is also concluded that a coarse-grid global climate model could be a helpful tool in a regional climate recognition. However, whether at a regional or local scale, it is recommended that a specially-configured version of a Regional Climate Model (RCM) based on Global Climate Model (GCM) boundary conditions be used in similar reconstructions

Reconstructing dynamics of the Baltic Ice Stream Complex during deglaciation of the Last Scandinavian Ice Sheet

Landforms left behind by the last Scandinavian Ice Sheet (SIS) offer an opportunity to investigate controls governing ice sheet dynamics. Terrestrial sectors of the ice sheet have received considerable attention from landform and stratigraphic investigations. In contrast, despite its geographical importance, the Baltic Sea remains poorly constrained due to limitations in bathymetric data. Both ice-sheet-scale investigations and regional studies at the southern periphery of the SIS have considered the Baltic depression to be a preferential route for ice flux towards the southern ice margin throughout the last glaciation. During the deglaciation the Baltic depression hosted the extensive Baltic Ice Lake, which likely exerted a considerable control on ice dynamics. Here we investigate the Baltic depression using newly available bathymetric data and peripheral topographic data. These data reveal an extensive landform suite stretching from Denmark in the west to Estonia in the east and from the southern European coast to the Åland Sea, comprising an area of 0.3 million km2. We use these landforms to reconstruct aspects of the ice dynamic history of the Baltic sector of the ice sheet. Landform evidence indicates a complex retreat pattern that changes from lobate ice margins with splaying lineations to parallel mega-scale glacial lineations (MSGLs) in the deeper depressions of the Baltic Basin. Ice margin still-stands on underlying geological structures indicate the likely importance of pinning points during deglaciation, resulting in a stepped retreat signal. Over the span of the study area we identify broad changes in the ice flow direction, ranging from SE–NW to N–S and then to NW–SE. MSGLs reveal distinct corridors of fast ice flow (ice streams) with widths of 30 km and up to 95 km in places, rather than the often-interpreted Baltic-wide (300 km) accelerated ice flow zone. These smaller ice streams are interpreted as having operated close behind the ice margin during late stages of deglaciation. Where previous ice-sheet-scale investigations inferred a single ice source, our mapping identifies flow and ice margin geometries from both Swedish and northern Bothnian sources. We anticipate that our landform mapping and interpretations may be used as a framework for more detailed empirical studies by identifying targets to acquire high-resolution bathymetry and sediment cores and also for comparison with numerical ice sheet modelling.</p

Reconstruction of the ice/bed interface conditions under the Weichselian ice sheet, central west Poland (Wielkopolska)

Wydział Nauk Geograficznych i GeologicznychCelem niniejszej pracy było zrekonstruowanie, na podstawie analiz sedymentologicznych i eksperymentów laboratoryjnych ze ścinania gliny, z nastawieniem na warunki termo-mechaniczne, warunków subglacjalnych, występujących pod lądolodem vistuliańskim na terenie Polski północno-zachodniej (Wielkopolska). Ponadto, postawiono sobie za cel określenie wpływu tych warunków na dynamikę lądolodu. Uzyskane dane wskazują, że pod transgredującym lądolodem rozwijały się obszary przymarznięte, suche bądź nasycone wodą i podatne na deformacje. Obszary zmarznięte stanowiły część subglacjalnej zmarzliny, która na terenie Wielkopolski prawdopodobnie miała charakter wyspowy. Deformowanie podłoża zachodziło z różną intensywnością w zależności od reżimu termalnego, który był istotnym czynnikiem warunkującym dynamikę lądolodu i od rozmieszczenia w strefie bazalnej obszarów mobilnych (nasyconych wodą) i stabilnych (zamarzniętych). Na podstawie badań sedymentologicznych wyróżniono cztery facje termodynamiczne. Dwie z nich odzwierciedlają warunki ciepłe i mokre pod lądolodem, a kolejne dwie są typowe dla wolno poruszających się, suchych i zimnych lodowców. Rozmieszczenie tych facji nie jest przypadkowe. Wzdłuż stref marginalnych i międzystrumieniowych dominują facje ‘zimne, suche i wolne’, natomiast w osiowych częściach strumieni lodowcowych znaleźć można facje ciepłe, wilgotne, typowe dla szybko płynących lodowców. Doświadczenia laboratoryjne i badania mikroskopowe pokazały, że każdy, centymetrowej miąższości, horyzont gliny odzwierciedla odmienne warunki depozycji i deformacji. Uzyskane wartości odkształceń były bardzo niskie, rzędu 101. Fakty te podkreślają znaczenie ślizgu bazalnego w szybkim ruchu lądolodu vistuliańskiego na terenie Polski północno-zachodniej.The aim of this study was to reconstruct the subglacial processes at the ice/bed interface based on sedimentological data, especially the thermo-mechanical conditions beneath the Weichselian ice sheet in central west Poland (Wielkopolska), and to determine their influence on the dynamics of the ice sheet. The obtained data indicate that frozen, dry, wet, and mobile spots occurred beneath the advancing ice sheet. The cold patches were part of a subglacial permafrost, which was at least discontinuous in Wielkopolska. The deformation of the substratum during the early stages of the ice advance occurred at different levels of intensity, mainly in accordance with the thermal regime at the ice/bed interface, which was probably a crucial factor for controlling the ice sheet dynamics. The spatial arrangement and frequency of thermally controlled sticky-spots as well as warm mobile patches influenced the behaviour of individual ice streams. Based on sedimentological analysis, four thermo-mechanical facies were distinguished. Two representative of slower ice, dry and cold subglacial conditions and two typical of a ‘wet’, warm, and fast ice. The thermo-mechanical facies have a non-random location, thereby revealing the relationship between subglacial conditions and ice sheet dynamics. Slow moving, cold-based ice occurred along ice sheet margins and inter-stream areas, while fast-moving, warm-based, and well-lubricated ice sole is typical of the axial parts of ice streams. The laboratory experiments and microscopical analyses showed that each cm-thick till layer reflects specific hydro-mechanical. The obtained strains were as low as 101. These facts emphasise the role of basal sliding in fast ice stream flow

Reconstruction of the ice/bed interface conditions under the Weichselian ice sheet, central west Poland (Wielkopolska)

Wydział Nauk Geograficznych i GeologicznychCelem niniejszej pracy było zrekonstruowanie, na podstawie analiz sedymentologicznych i eksperymentów laboratoryjnych ze ścinania gliny, z nastawieniem na warunki termo-mechaniczne, warunków subglacjalnych, występujących pod lądolodem vistuliańskim na terenie Polski północno-zachodniej (Wielkopolska). Ponadto, postawiono sobie za cel określenie wpływu tych warunków na dynamikę lądolodu. Uzyskane dane wskazują, że pod transgredującym lądolodem rozwijały się obszary przymarznięte, suche bądź nasycone wodą i podatne na deformacje. Obszary zmarznięte stanowiły część subglacjalnej zmarzliny, która na terenie Wielkopolski prawdopodobnie miała charakter wyspowy. Deformowanie podłoża zachodziło z różną intensywnością w zależności od reżimu termalnego, który był istotnym czynnikiem warunkującym dynamikę lądolodu i od rozmieszczenia w strefie bazalnej obszarów mobilnych (nasyconych wodą) i stabilnych (zamarzniętych). Na podstawie badań sedymentologicznych wyróżniono cztery facje termodynamiczne. Dwie z nich odzwierciedlają warunki ciepłe i mokre pod lądolodem, a kolejne dwie są typowe dla wolno poruszających się, suchych i zimnych lodowców. Rozmieszczenie tych facji nie jest przypadkowe. Wzdłuż stref marginalnych i międzystrumieniowych dominują facje ‘zimne, suche i wolne’, natomiast w osiowych częściach strumieni lodowcowych znaleźć można facje ciepłe, wilgotne, typowe dla szybko płynących lodowców. Doświadczenia laboratoryjne i badania mikroskopowe pokazały, że każdy, centymetrowej miąższości, horyzont gliny odzwierciedla odmienne warunki depozycji i deformacji. Uzyskane wartości odkształceń były bardzo niskie, rzędu 101. Fakty te podkreślają znaczenie ślizgu bazalnego w szybkim ruchu lądolodu vistuliańskiego na terenie Polski północno-zachodniej.The aim of this study was to reconstruct the subglacial processes at the ice/bed interface based on sedimentological data, especially the thermo-mechanical conditions beneath the Weichselian ice sheet in central west Poland (Wielkopolska), and to determine their influence on the dynamics of the ice sheet. The obtained data indicate that frozen, dry, wet, and mobile spots occurred beneath the advancing ice sheet. The cold patches were part of a subglacial permafrost, which was at least discontinuous in Wielkopolska. The deformation of the substratum during the early stages of the ice advance occurred at different levels of intensity, mainly in accordance with the thermal regime at the ice/bed interface, which was probably a crucial factor for controlling the ice sheet dynamics. The spatial arrangement and frequency of thermally controlled sticky-spots as well as warm mobile patches influenced the behaviour of individual ice streams. Based on sedimentological analysis, four thermo-mechanical facies were distinguished. Two representative of slower ice, dry and cold subglacial conditions and two typical of a ‘wet’, warm, and fast ice. The thermo-mechanical facies have a non-random location, thereby revealing the relationship between subglacial conditions and ice sheet dynamics. Slow moving, cold-based ice occurred along ice sheet margins and inter-stream areas, while fast-moving, warm-based, and well-lubricated ice sole is typical of the axial parts of ice streams. The laboratory experiments and microscopical analyses showed that each cm-thick till layer reflects specific hydro-mechanical. The obtained strains were as low as 101. These facts emphasise the role of basal sliding in fast ice stream flow

Glacier ice structures infl uence on moraines developement (Hørbye glacier, Central Spitsbergen).

Geomorphological and basic sedimentological investigation of controlled moraine system was carried out at the ice surface and within the moraine complex zone of the Hørbye glacier (Central Spitsbergen). The Hørbye glacier creates controlled moraine chains regarding transversal fractures and longitudinal foliation. The forms parallel to the ice fl ow direction are represented by medial moraines, whereas transversal ones by thrustmoraines. Both arrangements are clearly visible. However, thrust and shear planes are more effective in creating forms, both on the ice surface and in the moraine complex. The longitudinal landforms are less distinct, moreover they are coarser-grained and worse rounded, in contrast to the material from shear and thrust plains which is fi ner and better rounded. The study area can be divided into three subzones: clean ice surface, debris covered ice fractures and moraine complex. The outer and inner sandur plain were not taken under consideration. It is suggested that present arrangement of both thrust or shear plains and longitudinal foliation controls formation of foreland relief. This hypothesis has a particular sense in understanding construction of modern sedimentary basins as well as the mechanism of terminoglacial relief formation with regend to ice structure

Is the coarse-grid Global Climate Model a useful tool for regional paleoclimate reconstruction?

This study considers the climate at the time of the Weichselian ice sheet maximum in Central Europe, especially in Poland, in respect of the NASA Educational version of Global Climate Model (EdGCM). The final results of the EdGCM simulations for the Last Glacial Maximum (LGM) are presented here and these have been analysed to determine whether or not they are useful for regional scale modelling; the problem being that, in a global climate model, both horizontal and vertical grid resolution is very low. Also, an attempt has been made to define the role of the ice megalobe which, in terms of the numerical coarse-grid model,covered the northern parts of Germany and Poland. The broad details of the climate during the Weichselian are defined and our results are compared with previous opinion. The influence of ice megalobe on regional climate is demonstrated and it is also concluded that a coarse-grid global climate model could be a helpful tool in a regional climate recognition. However, whether at a regional or local scale, it is recommended that a specially-configured version of a Regional Climate Model (RCM) based on Global Climate Model (GCM) boundary conditions be used in similar reconstructions

Depositional processes within the frontal icecored moraine system, Ragnar glacier, Svalbard.

The marginal zone of the Ragnar glacier has been divided into four zones: ice surface, proglacial lake, lateral moraine and frontal moraine complex. Detailed researches were carried out in the last one - frontal moraine complex consisting of three subzones: (1) outer moraine ridge, (2) culmination moraine ridge and (3) inner moraine plateau. The frontal moraine complex of the Ragnar glacier shows large variability of lithofacies and depositional processes. The aim of this study was to reconstruct the intensity and variability of depositional processes from early stage of the frontal ice-cored moraines creation till present situation. Debris fl ow processes, glaciofl uvial and glaciolacustrine sedimentation as well as aeolian activity and down- and backwasting are identifi ed as most important processes. Intensity of these processes has varied through the time. Presently the frontal ice-cored moraine complex of the Ragnar glacier is relatively stable, except few areas affected by the river or streams

The interplay between deformation and deposition in a Pleistocene push moraine : New insight from structural interpretation and area-depth-strain analysis of the growth strata

There are many examples suggesting that push moraine formation requires building up of the proglacial wedge and then post-depositional folding and/or faulting. Only a few studies have been carried out on syntectonic deposition and erosion within proglacial sediment wedges; however, the resulting growth strata were determined based on the high variability in thickness and occurrence of erosional unconformities across the deformed sequence. This study shows how structural interpretation and the area-depth-strain (ADS) balancing method of the growth strata can be applied to better understand the interplay between deformation and deposition within an evolving push moraine primarily composed of a folded sequence of a glaciofluvial fan. This approach, together with analysis of the onlap/overlap relationships, allowed us to determine the relative rate between deposition and deformation. Moreover it provides an insight into the topography of the push moraine that may be inherited not only from the geometry of deformation structures but also from depositional processes controlling the spatial distribution and thickness variation of the growth strata. This study also gives an opportunity to reconstruct the ranges of probable parameters to quantitatively describe the heavily eroded push moraine in terms of the primary topography, height and relative time frame within which it formed. In addition, the probable thermo-hydro-mechanical properties of the deformed strata are interpreted in terms of drained/undrained conditions of volume strain evidenced by structural data and possibilities of lateral flow from beneath synclines into anticlines indicated by ADS-based balancing