IRTG-StRATEGy - Climate

163-G 1.5/G 1.6

henry.wichura — Thu, 31 Mar 2016 09:10:46 +0000

01|2016 – 03|2021

Investigating geologic archives of changes in erosion rates and hillslope processes in response to climate forcing

The principal aim of these two Postdoc projects is to determine how climate shifts and variability influence the dynamics of surface processes and affect landscape evolution over various timescales. Given the demonstrated sensitivity of landscape denudation rates to precipitation along the steep slopes of the eastern margin of the Andean Plateau¹, we hypothesize that the generation of thick late Pleistocene sedimentary fill terraces is linked to wetter climate conditions, and possibly also to changes in the variability of rainfall. Modern station observations of weather and sediment transport provide a detailed perspective on how climate variability can affect surface processes, but modern records often span insufficient time periods to characterize aspects of the system that change slowly, yet fundamentally influence the rate at which sediment can be created and mobilized from the Earth’s surface. These aspects include shifts and successional changes in vegetation, the rates at which soil forms and evolves, local sediment storage capacity, and tectonic forcing. By combining data from (1) weather and stream stations, (2) sedimentary archives (lake sediment cores, fluvial fill terraces), and (3) paleoclimate and paleovegetation proxies, we will achieve a multi-temporal perspective on how landscapes respond to climate shifts and changes in climate variability. Parallel efforts to map active structures and their influence on modern river profiles will allow us to identify regions in which recent changes in tectonic forcing is unlikely. These observations will embody a holistic set of empirical observations with which numerical landscape evolution models can be tested and refined. Special attention will be paid to the roles of climate-dependent biological (vegetation) and chemical processes, which are often neglected in considerations of climate-driven landscape dynamics. The first Postdoc project [G 1.5] will focus on comparing modern and paleo-erosion rates derived from cosmogenic nuclides with modern and paleo-climate signals derived from stable isotopes in biomarkers, in each case sampling both modern sediment and sediment from dated fill terraces. The second Postdoc project [G 1.6] will focus on integrating the field data into numerical landscape evolution models, to better understand the effects of different timescales of forcing (e.g., ENSO versus glacial-interglacial forcing) and any changes in surface processes that may explain variations in sediment mobilization and transport (e.g., landslides/debris flows versus soil creep). This work will complement ongoing efforts to understand modern sedimentary dynamics in the intermontane basins of the Argentine Andes, where aggradation of modern rivers has been tentatively been linked to a shift in the amount and variability of rainfall recorded at stream gauge and weather stations in the same areas where the extensive late Pleistocene fill terraces occur. Furthermore, comparisons between the fill terraces and what appears to be a modern analog in the form of an active, 20 km² alluvial fan provides opportunities to relate processes occurring in the contributing area of the fan (e.g., frequent landslides and debris flows) to those that likely occurred during the late Pleistocene aggradational periods.

Working Package:

WP1 - Climate

Temporal Process:

Intermediate

Dr. Fabiana CastinoUniversity of Potsdam Dr. Heiko PingelUniversity of Potsdam Mitchell D'Arcy, Ph.D.GFZ Potsdam Dr. Stefanie TofeldePotsdam University Prof. Manfred Strecker, Ph.D.Potsdam University Prof. Dr. Ricardo AlonsoSalta University (ARG)Prof. Taylor Schildgen, PhD.GFZ Potsdam Prof. Dr. Fernando HongnSalta University (ARG)Dr. Elizabeth OrrUniversity of Potsdam

Bibliography:

¹Strecker and Bookhagen, 2012

163-G 1.4

Anonymous — Fri, 25 Sep 2015 10:10:18 +0000

10|2018 – 09|2021

Sources and transformation of organic carbon in the fold and thrust belt of the NW Argentinian pre-cordillera

M.Sc. Sophia DoschGFZ Potsdam Dr. Dirk SachseGFZ Potsdam Prof. Dr. Niels HoviusGFZ Potsdam Dr. Luis PalazzesiNational Museum of Sciences (ARG)Dr. Ricardo SzupianyNational University of the Littoral (ARG)Dr. Francisco LatosinskiNational University of the Littoral (ARG)

Organic carbon mobilized from soils (biospheric carbon) as well as from sedimentary rocks (petrogenic carbon) in orogenic ranges is now being recognized as a major component of the Earth’s carbon cycle. Long-term burial of modern biospheric carbon in oceanic sinks results in a removal of CO₂from the atmosphere, whereas oxidation of petrogenic carbon would add CO₂ to the atmosphere, hence impacting the long-term evolution of climate. However, our understanding of the processes controlling mobilization and potential oxidation of this carbon during transport, redeposition and remobilization downstream is limited, preventing a quantitative assessment of organic carbon fluxes and their changes over time.

We aim to understand sources and transformation of organic carbon originating from the NW Argentinian foothills of the Andes and deposited in the fold and thrust belt over various geological timescales. Fingerprinting the organic material using organic-geochemical, stable and radiogenic isotope-based approaches, we investigate organic carbon in modern soils, intramontane sedimentary basins and modern rivers draining the Andes along steep climatological gradients. Using these tools we aim to identify the tectonic and climatic drivers and estimate organic carbon fluxes and assess their importance on longer geological timescales.

10|2016 - 09|2019

Climatic, biotic and geomorphic drivers of the isotopic composition of terrestrial organic matter transported through fluvial systems draining the NW Argentinian Andes

The key question which this project aims to answer is how tectonic processes such as mountain-range uplift affect atmospheric circulation patterns and enforce subsequent hydrological changes. The NW Argentine Andes are an ideal location to study these processes, due to unique and characteristic circulations patterns associated with the South American Low Level Jet (SALLJ) as part of the SAMS, which were established as a consequence of the topographic growth of the Andean orogen. Based on our previous studies, the imprint of these circulation patterns on modern stable water-isotope ratios is reasonably well understood. Here, we plan to conduct catchment investigations to understand and provide a sound base to decipher the development of such tectonically forced hydrological patterns during the geological past. In particular, we will study terrestrial climate archives in the intermontane basins along and across the NW Argentine Andes representing different episodes of range uplift and orographic-barrier formation during the last 10 Ma. As a paleohydrological proxy, we will employ the hydrogen stable isotope composition of leaf wax lipids (δDwax), which has been shown to record the δD values of meteoric plant-source water as well as terrestrial evapotranspiration, to identify changes in moisture source area (i.e. before and after the establishment of the SALLJ), and to record the onset of aridity in the basins of the orogen interior. In addition, the stable carbon-isotope composition of these compounds (δ¹³C_wax) will be analyzed to assess changes in vegetation cover from C3 to aridity adapted C4 plants. By taking this approach into the spatial domain, i.e. using multiple terrestrial archives from different basins along (N-S) and across (E-W) the Andes, we will identify past dynamics of atmospheric processes and asses these changes in the context of mountain-range uplift. The PhD candidate will focus on understanding the isotopic characteristics of leaf waxes and their climatic and biotic (i.e. vegetation distribution) drivers in modern catchments. By studying the modern hydrological gradient across (E-W) and along (N-S) the orogen and its imprint on leaf-wax stable isotope ratios, we will develop a sound base to apply this proxy on a variety of terrestrial climate archives from the last 10 Ma.

Working Package:

WP1 - Climate

Temporal Process:

Long Term

Dr. Marisa RepaschGFZ Potsdam Dr. Dirk SachseGFZ Potsdam Prof. Dr. Achim BrauerGFZ Potsdam Dr. Luis PalazzesiNational Museum of Sciences (ARG)

163-G 1.3

Anonymous — Fri, 25 Sep 2015 10:09:36 +0000

10|2018 – 09|2021

Reconstructing past climatic changes from lacustrine deposits II

Lic. Paula Andrea VignoniGFZ Potsdam Prof. Dr. Achim BrauerGFZ Potsdam Dr. Francisco CordobaJujuy University (ARG)Dr. Liliana LupoJujuy University (ARG)

Together with our partners in Argentina we plan to regionally extend our investigations and establish a transect from the moist area around Jujuy (ongoing project on Yala lakes) into the dry Puna Plateau which is characterized by internally drained basins with ephemeral playa lakes or salar sytems. Presently, there are only very few low-resolution studies in this region of the Central Andes, e.g. from the Salar de Atacama (Bobst et al. 2001; Lowenstein et al. 2003) and Laguna Pozuelos (McGlue et al. 2013). These studies suggest that, in contrast to the extreme dry present day conditions, climate has been wet during several periods of the last glaciation but also during the early and mid Holocene. Some of these wet periods coincide with maxima in January insolation at 15°S, but others do not. On the other hand, the recent extreme dry climate also coincides with an insolation maximum, indicating that the mechanisms causing wet periods are still not fully understood. We propose to study a sediment core from a playa lake to investigate for the first time such environment with high-resolution methods. Proposed sites are the Centenario and Ratones playa lakes, where also the 'Eramine' company is currently working. In case we get access of long cores from Eramine we will study glacial and interglacial wet periods. If this will not be possible, we will use the new drilling system from our partner at University of Jujuy to take up to 10 m long cores that will allow us to study Holocene wet periods in detail. This project could establish a link to a resources project.

10|2015 – 09|2018

Reconstructing past climatic changes from lacustrine deposits I

Paleoclimate analyses of lacustrine sediments has provided essential insights into decadal to millennial-scale climate variability and its driving mechanisms. Lake basins are ideal sediment traps that continuously record environmental and climatic evolution. New analytical approaches now even allow for deciphering the timing and dynamics of abrupt climate changes and extreme hydrometeorological events causing short-term catchment runoff at seasonal resolution. The project aims at investigating sediment records of presently saline lakes in the Altiplano-Puna plateau. The Puna region is promising for reconstructing past variations in moisture availability at regional scales because of the very strong gradient in precipitation over short distances. This project, will apply identical analytical procedures to two lake sites in locations with significant differences in present-day precipitation. The main scientific goals and questions to be addressed include (1) testing previous ideas of wetter conditions during times of insolation maxima in January driven by variations in the Earth’s orbital parameters; (2) investigating both wetter and drier millennialscale intervals with respect to centennial and decadal-scale oscillations in moisture availability; (3) testing if the Younger Dryas cold period is reflected by wet or dry conditions in NW Argentina; and (4) testing the hypothesis that changes in climatic boundary conditions can cause changing frequencies of extreme meteorological events. To achieve these goals, we will first conduct a thorough site survey of several lake basins for coring in the Salta region. Main criteria for site selection are differences in precipitation regimes, basin morphology and type of sediment infill. Coring two lake basins is planed to be conducted in fall 2016 using the GFZ Niederreither system. Sediment analyses include sedimentological and micro-facies analyses on thin sections, high resolution (200 micron) micro-XRF scanning, organic and inorganic carbon determination, AMS-C¹⁴ dating, mineralogical analyses, and stable oxygen and carbon isotope analysis on carbonates.

Working Package:

WP1 - Climate

Temporal Process:

Intermediate

Prof. Dr. Achim BrauerGFZ Potsdam Dr. Francisco CordobaJujuy University (ARG)

163-G 1.2

Anonymous — Fri, 25 Sep 2015 10:08:52 +0000

10|2018 – 09|2021

The role of mass wasting in glacial forelands of the Andes

M.Sc. Elisabeth SchönfeldtPotsdam University Prof. Oliver Korup, PhD.Potsdam University Dr. Diego WinocurBuenos Aires University (ARG)

Large segments of the Andean foreland have been repeatedly shaped by Quaternary glaciations. The many diagnostic landforms include large glacial lakes, staircases of moraine ridges, and extensive outwash plains, and have inspired generations of Quaternary geologists to reconstruct the processes, magnitude, and timing of ice build-up and decay along the mountain front, adding to a reference chronology of Southern hemisphere glaciations. What only a few of these studies have noticed are several hundreds of very large (>>10⁶m³) mass-wasting deposits that fringe the Andean foreland. Many of these debris mounds intersect with many well-dated moraine ridges or former meltwater-lake shorelines and offer exciting opportunities of exploring the hitherto largely unknown role of mass wasting in the glacial forelands of the Andes.

Studying the timing of these large landslides provides a stringent test for models of paraglacial landscape evolution. Preliminary work on large landslides glacial moraines indicates that moraines can fail catastrophically several thousand years after they formed. Several landslide bodies entered former glacial lakes shown by distinct horizontal breaks in landslide deposit morphology, thus raising the possibility of past and future landslide tsunamis.

The project aims to understand what we can learn from and what can we generalize about the mass-wasting activity of low-gradient glacial forelands. The Andean foreland may well host the largest cluster of (relatively) dated large, low-gradient landslides on Earth, which so far has been elusive in studies of the Andean sediment cascade. How does this estimate compare to sediment transport data, and what do we learn about sediment transfer from glaciated mountain belts to their proximal forelands?

10|2015 – 09|2018

Rock slides vs. rock glaciers: feeding the central Andean sediment cascade

This project explores the role of both large (>10⁶ m³) catastrophic rock slides and rock glaciers as prime movers of the central Andean sediment cascade. Recent hypotheses concerning the triggers of large non-volcanic bedrock landslides in the central Andes favor earthquakes, judging from the distribution of tell-tale landslide deposits with respect to active faults and shallow seismicity. Rock glaciers share a very similar topographic niche, but are traditionally viewed as diagnostic of sporadic alpine permafrost, though they may have also originated from earthquake-triggered supraglacial rock slides. Rock slides and rock glaciers are not only voluminous point sources of coarse debris, but also decisive barriers to incoming sediment flux. The aim of this project is to quantify to first order the regional net balance between such sediment release and sequestration by large rock slides and rock glaciers in central Andean headwaters using a multi-scale methodology: First, we will expand an existing regional inventory of large landslides and rock glaciers in the region to quantify the spatial pattern, topographic characteristics, and volumetric distribution of large Andean debris deposits from digital topography and remote sensing data. We will compare classic operator-based mapping with state-of-the-art automated object-oriented mapping techniques. Second, fieldwork will involve local ground truthing of landslide and rock-glacier geometries and provide vital input data for gauging regional volumetric budgets of denudation rates and intermittent sediment storage. We will estimate the fraction of valley fills causally linked to catastrophic slope failure and rock-glacier dynamics to gauge the overall relevance of catastrophic hillslope input to the central Andean sediment cascade. Samples collected in the field will further provide age constraints of strategically selected rockslide and rock-glacier surfaces or correlate backwater sediments with ¹⁴C, ¹⁰Be, lichenometry or dendrochronology, depending on available samples. Third, we will quantify metrics of geomorphic impact of these deposits on the fluvial network (changes in fluvial transport capacity, formation of knickpoints, epigenetic bedrock meanders, etc.), and the sediment cascade (barrier lakes, floodplain aggradation, etc.). We will expand existing numerical models of channel adjustment to landslide and rock glacier impacts to estimate fluvial response and recovery times. Similar work that we conducted in other regions revealed decisive controls of large landslide deposits on bedrock channel geometry, and the size and age distribution of valley fills that are potential sinks of alluvial georesources. Moreover, large river-blocking rock slides and rock glaciers may form important temporary buffers to incoming, and potentially adverse, sediment pulses from local disturbances.

Working Package:

WP1 - Climate

Temporal Process:

Short Term

M.Sc. M.Sc. Julia DrewesPotsdam University Prof. Oliver Korup, PhD.Potsdam University Prof. Dr. Stella MoreirasCuyo National University (ARG)

163-G 1.1

Anonymous — Fri, 25 Sep 2015 10:08:11 +0000

10|2018 – 09|2021

GNSS-based remote sensing: Innovative observation of key hydrological parameters in the central Andes

M.Sc. Nikolaos AntonoglouGFZ Potsdam Prof. Dr. Jens WickertGFZ Potsdam Prof. Dr. Bodo BookhagenPotsdam University Prof. Dr. Alejandro De la TorreAUSTRAL University (ARG)Prof. Dr. Andreas GüntnerGFZ Potsdam Dr. Torsten SchmidtGFZ Potsdam

The central Andes are characterized by a steep climatic gradient where key hydrologic variables change across short distances. One of the largest unknown component in this environment is the storage of water in the atmosphere, soil (soil moisture) and the snow height (or snow water equivalent). Both are parameters that can be quantified with modern remote sensing technology and we seek to enhance our understanding of the complete water fluxes in this environment – especially the highly dynamic fluxes that are often associated with hydrometerological extreme events.

In the past two decades, innovative GNSS (Global Navigational Satellite Systems) based remote sensing techniques were successfully tested and established and the resulting observations evolved into an important data source for numerous meteorological applications. The most prominent example for this development is the operational use of GNSS-based temperature and water vapor data to improve day-by-day regional and global weather forecasts since 2006. The exploitation of Earth reflected signals (GNSS Reflectometry, GNSS-R), however is not yet operationally applied and still focus of international research to reach operational application level as well. GNSS data provide an excellent opportunity to study the dynamics of hydrometeorological extreme events, because of the very high sampling interval.

This project relies on close collaboration with Argentinean researchers that maintain a regional GNSS ground network. In the framework of this project, new stations at specific, key locations will be installed and the data used to decipher hydrologic process. This project requires strong quantitative skills and thorough environmental knowledge.

10|2015 – 09|2018

Characterization of atmospheric processes related to hydro-meteorological extreme events over the south-central Andes

Extreme rainfall events fundamentally impact erosion and deposition. The combination of the South American Monsoon System (SAMS) and high topography of the Central Andes constitutes the most important drivers for the highly asymmetric distribution of rainfall. In light of these conditions and climate variability involving the SAMS, the South American Convergence Zone, the El Niño Southern Oscillation, and the Southern Hemisphere Westerlies, meteorological observations and detailed analysis of the atmospheric circulation over South America at various spatiotemporal scales are required to create models and derive predictions of the response of surface-process systems to climate change. For more than a decade, the GPS radio occultation (RO) method has offered a promising tool for the global characterization of atmospheric temperature and tropospheric humidity. Here, we will use ground (weather stations, radiosonde stations, and S band radar stations) and space-based (RO and other satellites) observations and meteorological re-analyses (ERA interim, ERA40) to obtain a detailed view of the dynamics of the SAMS, the related humidity fields, and precipitation patterns. In addition, this approach will help to decipher the characteristics of annual and seasonal variability, and the linkage to extreme precipitation events. The considered time scale will range from the time since RO observations are available (since 2001) and extend to the beginning of the ERA40 dataset covering the 1950s. Finally, we will associate the combined observational and re-analysis data with their spatiotemporal variation to QBO and ENSO events for a better understanding of the interplay between natural atmospheric variability and the observed humidity/rainfall amount and distribution. Due to a recent southward shift of the SAMS and an amplification of the jet stream, coupled with increased southward moisture transport from Amazonia and annual precipitation, it can be expected that variations in atmosphere dynamics, tropopause structure, and gravity-wave activity will occur, an issue that will also be addressed in this study. Combined, the results of this project will be essential to understanding regional erosional and sedimentological processes on short timescales, and will help clarify the couplings between climate and surface-process reflected in geological archives of intermontane and foreland basin fills.

Working Package:

WP1 - Climate

Temporal Process:

Short Term

Dr. Maryam Ramezani ZiaraniGFZ Potsdam Prof. Dr. Bodo BookhagenPotsdam University Dr. Torsten SchmidtGFZ Potsdam Prof. Dr. Jens WickertGFZ Potsdam Prof. Dr. Alejandro De la TorreAUSTRAL University (ARG)