Estimations of accumulation area ratio (AAR) and equilibrium line altitude (ELA) were carried out on the Southern Patagonia Icefield. The icefield lies on the border between Chile and Argentina on the southern tip of South America. It is the largest mid-latitude ice mass in the world but despite this fact little research has been conducted in the area. The main reasons for this are most likely the harsh weather conditions and remoteness of the area. However, since icefield’s act as a source for fresh water and as an indicator of climate change more research is crucial. This study focuses on three objectives: to map the snow cover, to estimate AAR and ELA and to discuss their variations during the period 2000 to 2010. The Moderate Resolution Imaging Spectroradiometer (MODIS) is particularly useful for studying cloudy areas because it’s high temporal resolution increase the chances of acquiring cloud- free images. Satellite images were processed, classified and analyzed. The classification results yielded large interannual variations but also congruity. The pattern of the snow cover suggest substantial wind control on snow accumulation, particularly snow deposition on eastern slopes. No statistically significant trends of AAR and ELA could be detected, although, a vague decrease in AAR and increase in ELA is recognized. Average values of AAR and ELA estimated over the period yields lower AARs and higher ELAs than previously suggested. The average AAR is calculated to be 0.66. Average ELA is estimated to be 970 m.a.s.l. and 1270 m.a.s.l. for the western and eastern sides, respectively.

This study presents a comprehensive overview of the current state of the Milne Ice Shelf and how it has changed over the last 59 years. The 205 ±1 km2 ice shelf experienced a 28% (82 ±0.8 km2) reduction in area between 1950 – 2009, and a 20% (2.5 ±0.9km3 water equivalent (w.e.)) reduction in volume between 1981 – 2008/2009, suggesting a long-term state of negative mass balance. Comparison of mean annual specific mass balances (up to -0.34 m w.e. yr-1) with surface mass balance measurements for the nearby Ward Hunt Ice Shelf suggest that basal melt is a key contributor to total ice shelf thinning. The development and expansion of new and existing surface cracks, as well as ice-marginal and epishelf lake development, indicate significant ice shelf weakening. Over the next few decades it is likely that the Milne Ice Shelf will continue to deteriorate.

Palaeoenvironmental investigations from the Lake Plav catchment of the Prokletije Mountains in Montenegro and Albania, allowed primarily climatic change and anthropogenic influences during the Late Holocene and particularly the Little Ice Age (LIA) to be identified. Three sediment cores were analysed, two from Lake Plav (904 m a.s.l., cores LPCA and LPCB) and one from the upper catchment site of Lake C in Buni i Jezerces (1754 m a.s.l., core BJC1). These sediments were analysed for a variety of proxies including pollen, ostracoda, organic content, magnetic susceptibility and particle size. Chronologies for each sediment core were constructed using AMS radiocarbon, 210Pb and 137Cs dating techniques. The lower sites provided a record of past flood events, anthropogenic influences, lake development and infilling that have occurred since c. AD 500. Core BJC1 provided longer-term data since c. 2720 BC, providing complementary records of Pediastrum and thermophilous arboreal types, identified following a catchment vegetation survey. Glacial geomorphological mapping of the Maja e Koljaet glacier in Buni i Jezerces, Albania, enabled a catchment specific palaeotemperature record to be constructed from AD 1859 to the present. Glacial features were dated using lichenometry before degree-day modelling enabled temperature reconstruction. The palaeotemperature reconstruction for the Albanian Little Ice Age glacial maximum (LIAGM) suggests that temperatures were 0.9°C below the 1980-2008 annual temperature mean. This work also provided the first record of glacial extent during the LIA in Albania, indicating that the Albania LIAGM occurred c. AD 1859, around a decade after the European LIAGM and two decades before that of Montenegro. Anthropogenic indicators were used to reconstruct human activity in the catchment, which suggested that arable farming was pursued throughout the Medieval Warm Period (MWP; c. AD 800-1090) and continued during a period of transition to the LIA, between c. AD 1090 and AD 1300. The LIA (c. AD 1300 - 1860) was characterised by an abrupt Alnus decline, thought to be the result of anthropogenic clearance of the floodplain and reduction of both arable and thermophilous types. During the LIA sedimentation rates were up to 1.41 + 0.17 cm yr-1 at Lake Plav causing lake infilling and shallowing allowing wetland expansion c. AD 1570. The result of lake infilling is highlighted during the early 20th century, when the lake extent fell by around 42% as a result of climatic amelioration post-LIA causing lake levels to fall and wetland indicators to decline. The inferred past climatic changes from the Lake Plav catchment are compared to data from around the Mediterranean and Southern Europe. This allows identification of the climatic influences affecting the site during the Late Holocene. Catchment records have provided evidence of cooler and wetter conditions coeval to the occurrence of solar minima such as the Wolf, Spörer and Maunder minima. Overall, the records suggest that continental atmospheric circulation patterns such as the North Sea-Caspian Pattern (NCP) and East Atlantic-West Russia pattern (EA-WR), dominated the site until the late 1800s, when records become more synchronous with the NAO index and Mediterranean/Southern European data.

A series of small mounds (&lt; 3m) were sampled in the foreland of Midtdalsbreen outlet glacier, southern Norway. These landforms were interesting, especially at site number 1 because they were located very close to a higher Little Ice Age (LIA) moraine (&gt; 5 m), thereby informing the dynamic of the glacier after the LIA at this location. It was yet to determine if these specific mounds are controlled moraines. If they are controlled moraines, then this would have implication for the glacier dynamics and the geometry of the snout after the LIA. It could be determined, based on the landform record evidence, whether the ice at the snout of Midtdalsbreen was thin and cold shortly after the LIA. Furthermore, whether the landscape was deglaciated by downwasting and then by backwasting was the main question addressed in relation to the nature of the mound and the thickness of ice at the snout during and after the LIA. In order to better understand the nature of the landform record and the mounds near the LIA moraine, satellite imagery coupled with careful field investigations were used in the foreland of the Midtdalsbreen outlet glacier. A geomorphological map was produced, and it was useful to put the mounds in a geographical context. Further sedimentological investigation; including clast-shape analyze, produced more evidence about the inner nature of these landforms. Both few controlled moraines and other landforms throughout the glacier foreland indicate that the ice geometry for Midtdalsbreen, shortly after the LIA was such that the snout of the glacier was a thin sheet of ice flowing against the previously deposited LIA moraine. The sedimentology of the controlled moraine is such that the sediments are deposited in steeply dipping layers, and they could even be misinterpreted as permafrost terrains at first glimpse. However, other sedimentological evidences such as the presence of sorted sand and sometimes dipping beds of gravels in addition to the geomorphological mapping make it meaningful to interpret few of the mounds as controlled moraines. A modern analogue to these controlled moraines is dirt cones present on top of the glacier snout as well as controlled moraines a few hundred of meter from the snout. Observations both on the glacier snout and on the foreland involve that dirt-cones later evolve into these sedimentological hummocky units with steeply dipping layers within the paleo-landscape. These observations constrain the thickness of ice at the snout of Midtdalsbreen after the LIA as well as the glacier dynamic during its melt: for controlled moraines to be generated by glaciers, these accumulations of sediments would have to thaw by downwasting and then by backwasting, directly at the glacier snout. This process -comprising of different stages- allows enough time to deposit controlled moraine. It is then a thin, cold-based sheet of ice which is by the end responsible for the deposition of such a landform record. There was even dead-ice present on the landscape at that point. After deposition of dirt cones on top of the ice, important meltwater action is contributing to the glacifluvial origin of these hummocks which evolve from dirt-cones onto the glacier, to ice-cored moraines, and then to controlled moraines onto the foreland. Details about the multistage processes leading to the formation of controlled moraines is also at the center of the investigations. / <p>Updated version, september 2019.</p>

Beitrag zu geodätischen Arbeiten im Gebiet des subglazialen Lake Vostok anläßlich einer Festschrift zum 65. Geburtstag von Prof. Reinhard Dietrich.

Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references. / In the spring and summer within the ablation zone of the Greenland Ice Sheet (GrIS), meltwater drains to the ice sheet bed through an evolving network of efficient channelized and inefficient distributed drainage systems. Distributed system drainage is a key component in stabilizing GrIS velocity on interannual time scales and controlling geochemical fluxes. During the spring and summer of 2011 and 2012, I conducted fieldwork at a large outlet glacier in southwest Greenland underlain by metamorphic silicate rocks. Data collected from a continuous 222Rn monitor in the proglacial river were used as a component of a mass balance model. I demonstrated that Jdis, the 222Rn fraction derived from the distributed system, was >90% of the 222Rn flux on average, and therefore, 222Rn can be used as a passive flow tracer of distributed system drainage. Supraglacial meltwater runoff estimated using two independent models was compared with ice velocity measurements across the glacier's catchment. Major spikes of Jdis, occurred after rapid supraglacial meltwater runoff inputs and during the expansion of the subglacial channelized system. While increases in meltwater runoff induced ice acceleration, they also resulted in the formation of efficient subglacial channels and increased drainage from the distributed system, mechanisms known to cause slower late summer to winter velocities. Sr, U, and Ra isotopes and major and trace element chemistry were used to investigate the impact of glacial hydrology on subglacial weathering. Analysis of partial and total digestions of the riverine suspended load (SSL) found that trace carbonates within the silicate watershed largely controlled the 'Sr/'Sr ratio in the dissolved load. Experiments and sampling transects downstream from the GrIS demonstrated that [delta]234U in the dissolved phase decreased with increasing interaction with the SSL. The (2 2 8Ra/2 26Ra) value of the dissolved load was significantly higher than that of the SSL and therefore, was not the result of the source rock material but of extensive mineral surface weathering and the faster ingrowth rate of 228Ra (t1 2=5.75 y) relative to 22 6Ra (t112=1600 y). In summary, extensive, repeated cycles of rapid supraglacial meltwater runoff to subglacial drainage networks leads to increased distributed system drainage and mineral weathering. / by Benjamin Shawn Linhoff. / Ph. D.

No description available.

No description available.

Surge-type glaciers experience cyclical variations between long periods of slow flow, followed by shorter periods of rapid flow. These glaciers have been thoroughly analysed in many regions, but detailed studies of surging in the Canadian Arctic are lacking. This thesis provides the first comprehensive reconstruction of the dynamics of Iceberg and Airdrop glaciers, located on western Axel Heiberg Island, and reveals detailed observations of a surge for the first time in the Canadian Arctic. A variety of remotely sensed data, including historical aerial photographs, declassified intelligence satellite photographs, optical satellite imagery (e.g., ASTER, Landsat), and synthetic aperture radar data (e.g., ERS-1, ERS-2) were used to quantify changes in terminus position, ice velocity, and ice thickness since the 1950s. A surge initiated at the terminus of Iceberg Glacier in 1981 and terminated in 2003, suggesting an active phase length of 22 years. High surface velocities, peaking at ~2300 m a⁻¹ at the terminus in summer 1991, were accompanied by a terminus advance of >7 km over the period 1981-1997 and a large transfer of mass down-glacier, causing significant median surface elevation changes reaching >3 ± 1 m a⁻¹ across the entire trunk width. The ensuing quiescent period has seen a continual decrease in flow rates to an average centreline velocity of 11.5 m a⁻¹ in 2020-2021, a gradual steepening of the glacier surface, and a terminus retreat of >2.5 km. Observations on Airdrop Glacier show a continuous advance totalling ~6 km since 1950 and notably less variability in its surface velocities in comparison to Iceberg Glacier. This advance can be attributed to consistently high flow rates of Airdrop’s entire surface, resulting in significant thickening near its terminus since at least 1977. However, velocities have more than halved within the last 15 years, but without any clear evidence of previous fast flow events, we cannot confirm whether Airdrop’s behaviour is cyclic in nature and therefore characteristic of a surge. Instead, Airdrop Glacier could be experiencing a delayed response to positive mass balance conditions of the Little Ice Age, and its recent slowdown could be indicative of a gradual adjustment to recent climatic conditions.

During the latter half of the 20th century until present day there has been an unprecedented rise in global annual mean temperatures accompanied by rising sea levels and a decrease in Northern Hemisphere snow cover, which if it continues will lead to widespread disruption of climate patterns, ecosystems, and present-day landscapes. It is therefore of critical importance to establish an expanded network of paleoclimate records across the globe in order to better assesses how the global climate system has changed in the past, that we may create a metric by which to address modern change. Herein is presented a7,700 years record of Holocene climatic and environmental variability in Sermilik Valley, located on Ammassalik Island, SE Greenland. This objective of this study is to determine the timing of major Holocene climate transitions as expressed in the physical, elemental, and geochemical parameters preserved in the 484 cm sediment record of Lower Sermilik Lake. Major transitions observed in this study include the deglaciation of Sermilik Valley, the onset and termination of the Holocene Climatic Optimum, the transition into neoglacial conditions, and the Little Ice Age.