Susan Ivy Ochs

Bio: Susan Ivy Ochs is an academic researcher from ETH Zurich. The author has contributed to research in topics: Glacier & Glacial period. The author has an hindex of 5, co-authored 5 publications receiving 118 citations.

Limited Pliocene/Pleistocene glaciation in Deep Freeze Range, northern Victoria Land, Antarctica, derived from in situ cosmogenic nuclides

Abstract: The question of how stable the climate in Antarctica has been during the last few million yearscompared to the rest of the planet is still controversial. This study attempts to add new information to thediscussion by reconstructing the timing and spatial extent of glacial advances in northern Victoria Land overtens of thousands to millions of years. In Terra Nova Bay region, surface exposure ages and erosion rates ofglacially rounded bedrock and glacial erratics have been determined using the cosmogenic nuclides 3 He, 10 Be and 21 Ne. Three morphological units have been analysed. They yield minimum ages of 11 to 34 ka,309 ka, and 2.6 Ma, respectively. Erosion rates were as low as 20 cm Ma -1 since middle Pliocene time.Taking erosion into account, the oldest surface is 5.3 Ma old. Pleistocene glacier advances had considerableextent, reaching up to 780 m above modern ice levels, but have been restricted to the valleys since at leastmid-Pliocene. The existence of landscapes of mid-Pliocene age in northern Victoria Land implies that theclimatic stability of the McMurdo Dry Valleys is not unique within the Transantarctic Mountains, but ratherthe expression of a constantly cold and hyperarid climate regime in entire Victoria Land.

Redating the moraines in the Kromer Valley (Silvretta Mountains) – New evidence for an early Holocene glacier advance:

Abstract: Among the many well-preserved moraine systems that are found throughout the Austrian Silvretta Mountains, a set of prominent moraines in the upper Kromer Valley located in front of the ‘Little Ice ...

Exposure dating of a pronounced glacier advance at the onset of the late-Holocene in the central Tyrolean Alps:

Abstract: A two-phased moraine system in the high Alpine valley of Lisenser Langental in the Stubai Alps of western Austria is located in an intermediate morphostratigraphic position constrained by ‘Egesen S...

Mid-Holocene thinning of David Glacier, Antarctica: Chronologyand Controls

Abstract: . Quantitative satellite observations provide a comprehensive assessment of ice sheet mass loss over the last four decades, but limited insights into long-term drivers of ice sheet change. Geological records can extend the observational record and aid our understanding of ice sheet–climate interactions. Here we present the first millennial-scale reconstruction of David Glacier, the largest East Antarctic outlet glacier in Victoria Land. We use surface exposure dating of glacial erratics deposited on nunataks to reconstruct changes in ice surface elevation through time. We then use numerical modelling experiments to determine the drivers of glacial thinning. Thinning profiles derived from 45 10Be and 3He surface exposure ages show that David Glacier experienced rapid thinning up to 2 m/yr during the mid-Holocene (~ 6,500 years ago). Thinning stabilised at 6 kyr, suggesting initial formation of the Drygalski Ice Tongue at this time. Our work, along with terrestrial cosmogenic nuclide records from adjacent glaciers, shows simultaneous glacier thinning in this sector of the Transantarctic Mountains occurred ~ 3 kyr after the retreat of marine-based grounded ice in the western Ross Embayment. The timing and rapidity of the reconstructed thinning at David Glacier is similar to reconstructions in the Amundsen and Weddell embayments. In order to identify the potential causes of these rapid changes along the David Glacier, we use a glacier flow line model designed for calving glaciers and compare modelled results against our geological data. We show that glacier thinning and marine-based grounding line retreat is initiated by interactions between enhanced sub-ice shelf melting and reduced lateral buttressing, leading to Marine Ice Sheet Instability. Such rapid glacier thinning events are not captured in continental or sector-scale numerical modelling reconstructions for this period. Together, our chronology and modelling suggest a ~ 2,000-year period of dynamic thinning in the recent geological past.

What are the polar regions

Abstract: Advanced Planning Preparation Time: ~10 minutes 1. Review the instructions 2. Gather the necessary supplies. Lesson Summary Students will learn about the Polar Regions and find and classify images of different changing polar landscapes.

Antarctic glacial isostatic adjustment: a new assessment

Abstract: The prediction of crustal motions and gravity change driven by glacial isostatic adjustment (GIA) in Antarctica is critically dependent on the reconstruction of the configuration and thickness of the ice sheet during the Late Pleistocene and Holocene. The collection and analysis of field data to improve the reconstruction has occurred at an accelerated pace during the past decade. At the same time, space-based imaging and altimetry, combined with on-ice velocity measurements using Global Positioning System (GPS) geodesy, has provided better assessments of the present-day mass balance of the Antarctic ice sheet. Present-day mass change appears to be dominated by deglaciation that is, in large part, a continuation of late- Holocene evolution. Here a new ice load model is constructed, based on a synthesis of the current constraints on past ice history and present-day mass balance. The load is used to predict GIA crustal motion and geoid change. Compared to existing glacioisostatic models, the new ice history model is significantly improved in four aspects: (i) the timing of volume losses in the region ranging from the Ross Sea sector to the Antarctic Peninsula, (ii) the maximum ice heights in parts of the Ellsworth and Transantarctic Mountains, (iii) maximum grounding line position in Pine Island Bay, the Antarctic Peninsula, and in the Ross Sea, (iv) incorporation of present-day net mass balance estimates. The predicted present-day GIA uplift rates peak at 14-18 mm yr -1 and geoid rates peak at 4-5 mm yr -1 for two contrasting viscosity models. If the asthenosphere underlying West Antarctica has a low viscosity then the predictions could change substantially due to the extreme sensitivity to recent (past two millennia) ice mass variability. Future observations of crustal motion and gravity change will substantially improve the understanding of sub-Antarctic lithospheric and mantle rheology.

Ice Sheet Sources of Sea Level Rise and Freshwater Discharge During the Last Deglaciation

Abstract: We review and synthesize the geologic record that constrains the sources of sea level rise and freshwater discharge to the global oceans associated with retreat of ice sheets during the last deglaciation. The Last Glacial Maximum (∼26–19 ka) was terminated by a rapid 5–10 m sea level rise at 19.0–19.5 ka, sourced largely from Northern Hemisphere ice sheet retreat in response to high northern latitude insolation forcing. Sea level rise of 8–20 m from ∼19 to 14.5 ka can be attributed to continued retreat of the Laurentide and Eurasian Ice Sheets, with an additional freshwater forcing of uncertain amount delivered by Heinrich event 1. The source of the abrupt acceleration in sea level rise at ∼14.6 ka (meltwater pulse 1A, ∼14–15 m) includes contributions of 6.5–10 m from Northern Hemisphere ice sheets, of which 2–7 m represents an excess contribution above that derived from ongoing ice sheet retreat. Widespread retreat of Antarctic ice sheets began at 14.0–15.0 ka, which, together with geophysical modeling of far-field sea level records, suggests an Antarctic contribution to this meltwater pulse as well. The cause of the subsequent Younger Dryas cold event can be attributed to eastward freshwater runoff from the Lake Agassiz basin to the St. Lawrence estuary that agrees with existing Lake Agassiz outlet radiocarbon dates. Much of the early Holocene sea level rise can be explained by Laurentide and Scandinavian Ice Sheet retreat, with collapse of Laurentide ice over Hudson Bay and drainage of Lake Agassiz basin runoff at ∼8.4–8.2 ka to the Labrador Sea causing the 8.2 ka event.

Geomorphological applications of cosmogenic isotope analysis

Abstract: Cosmogenic isotope analysis involves the measurement of cosmogenic nuclides that have accumulated in the upper few metres of the Earth’s surface as a result of interactions between cosmic rays and target elements. The concentrations of these cosmogenic nuclides can provide quantitative estimates of the timing and rate of geomorphic processes. In dating applications the concentration of cosmogenic nuclides is interpreted as reflecting the time elapsed since a surface exposure event. However, over most of the Earth’s surface for most of the time the landsurface experiences incremental denudation and in these circumstances cosmogenic nuclide concentrations are related to the rate of denudation. Applications of event dating using cosmogenic isotopes include constructional landforms such as volcanic and depositional features, fault displacement, meteorite impacts, rapid mass movement, bedrock surfaces rapidly eroded by fluvial or wave action or exposed by glacial retreat, and the burial of sediment or ice. Str...