«Changing Polar Regions 25th International Congress on Polar Research March 17-22, 2013, Hamburg, Germany German Society for Polar Research Edited by ...»
decreased albedo, increased carbon sequestration and evaporative cooling, as well as altered vegetation composition. Hence, the question of when and how far the treeline advances is of particular interest. Reproductive capacity and the establishment of seedlings at the treeline are assumed to represent major processes that limit northward treeline expansion.
We investigate past treeline transitions by applying two different procedures. Our first approach is based on a detailed field survey, conducted in 2011 near the Taimyr Peninsula, North Siberian Lowland, during which we investigated the stand structure of Larix gmelinii at four different sites (between 70.6° N and 72.4° N) in the tundrataiga ecotone.
There is reason to suspect that different limitations govern the reproductive success across the arctic treeline along a north-south gradient. Based on our data we hypothesise that reproductive success in the north, at the species boundary, is mainly limited by the amount of seed-producing trees, whereas in more southern regions, with denser crown cover, competition is the main restricting factor. Between these edges of the tundra-taiga ecotone, we hypothesise temperature to be the most important factor controlling reproduction.
The second approach comprises a vegetation modelin order to test our hypothesis with different input-scenarios. In this next step, we want to investigate the influence of various driving factors on the reproductive success of L. gmelinii in the tundra-taiga ecotone and point out possible future changes of the treeline position in this region.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 SEA ICE MASS BALANCE INFLUENCED BY ICE SHELVES: THE
SIMBIS PROJECT - OBJECTIVES AND PRELIMINARY RESULTS
The overall goal of the SIMBIS project is to improve our understanding of formation processes and properties of Antarctic sea ice and how these are influenced by its snow cover and platelet ice. Platelet ice is ice that is formed in the water column from super-cooled water originating from ice shelf cavities. In order to achieve this goal, we will combine in-situ measurements with satellite observations and numerical studies. Measurements of sea-ice thickness, snow depth, and the under-ice plateletice layer thickness will reveal the role of ice shelves for sea-ice formation and its seasonality. Energy balance and measurements, focusing on optical properties, will be performed to describe thermodynamic properties of sea ice and its snow cover. In order to upscale the local measurements, we will analyze several data products from satellites and work towards new multi-sensor approaches for sea-ice analyses.
Numerical simulations will be used to quantify the mass contributions from snow and from platelet ice on regional and circumpolar scales. The first field campaign was performed on land-fast sea ice of Atka Bay close to Neumayer III station, Antarctic, between November 2012 and January 2013. Routine measurements of snow and sea-ice properties from July to January are performed annually by the wintering teams since 2011 and add to this project. We will give an overall introduction into the project objectives, methods and first results from the recent field campaign.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 SEDIMENTATION IN MAXWELL BAY (KING GEORGE ISLAND,
WEST ANTARCTIC PENINSULA) DURING THE UPPER HOLOCENE
Numerous studies have shown that the Western Antarctic Peninsula is currently experiencing a temperature increase that is higher than in other parts of Antarctica.
King George Island belongs to the South Shetland Islands that are located approx.
120 km west off the northern tip of the Antarctic Peninsula. On King George Island the ice sheet is waning with accelerating speed. Almost all tidewater glaciers in the adjacent coves of Maxwell Bay have already retreated on land. During austral summers meltwater discharge can be observed in these coves. The meltwater is loaded with suspended fine-grained material. This fine-grained material is transported in plumes out of the coves and settles in Maxwell Bay.
Results from sub-bottom profiles underline this observation. The profiles show different acoustic patterns: (1) Very well stratified layers down to 50 m below the seafloor in Maxwell Bay whereas (2) within the tributary fjords at water depths 200 m very thin, disturbed and often almost acoustically transparent packages have been recorded.
During RV Polarstern cruise ANT-XXIII/4, marine sediment cores were recovered along a profile from the eastern slope of Maxwell Bay. The cores were taken in highaccumulation areas at the entrances of Collins Harbor, Marian and Potter coves.
Results from radiocarbon dating of biogenic carbonate suggest that the cores cover approximately the last 2000 years.
Grain size distributions were measured in 1-cm steps in each core with a laser diffraction particle analyzer to be able to identify variations in grain size compositions in a very high resolution. The magnetic susceptibility (MS) parameter fluctuates throughout the cores. It is negatively correlated to the amount of total organic carbon (TOC) and biogenic opal, suggesting dilution of the MS signal through higher input of organic material.
We assume that the presence of fine-grained sediments appearing in the cores in Maxwell Bay reflect periods of intense glacier melting. This allows us together with other parameters to identify warmer and colder periods that are most likely related to Holocene climate fluctuations.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 CHALLENGES IN ANTARCTIC MARINE BIODIVERSITY AND FOOD
WEBS STUDIES: A TOP PREDATORS PERSPECTIVE
The Southern Ocean holds a diverse range of unique marine ecosystems.
Characterized by extreme environmental conditions, it provides habitats for highly adapted and specialized organisms and communities, some of which are targets of commercial exploitation. Furthermore, the Southern ocean are among the regions that are most susceptible to rapid ocean warming and acidification, two of the most pressing effects of global climate change. This presentation aims to highlight the most recent research work focused on Antarctic marine ecosystems, specifically on the feeding and foraging ecology of top predators (particularly penguins, albatrosses and seals), the development of methods applied to improve this knowledge (e.g.
quantifying methods for prey biodiversity, identication guides for prey), modelling tools to predict changes in the future and insights into the conservation of top predators in the Southern Ocean.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 ARCTIC MULTIYEAR ICE CONCENTRATION RETRIEVAL FROM SSM/I DATA
Global warming is most pronounced in the Arctic. The Arctic sea ice extent is a sensitive climate indicator. As a consequence of the strongly decreasing trend of yearly Arctic sea ice minimum in September, the area of multiyear ice, which has survived more than one summer, is decreasing too. Multiyear ice is important because it differs from first year ice in physical and biological respect. Multiyear ice is thicker and therefore conducts less heat from ocean to atmosphere, it has more resistance against deforming forces of wind and currents and it is populated by microorganisms which are at the beginning of the food chain. Therefore multiyear ice area and extent need to be determined as exactly as possible. In this study, we retrieve multiyear ice concentration with two existing methods, namely the NASA Team algorithm, Comiso’s algorithm, and a new developed algorithm, the NASA Team algorithm with dynamic tie points. Dynamic tie points are used in the second and third methods to compensate the seasonal impact of brightness temperature variation. To assess the performance of the three methods, analyses were made for the winters from 1998 to 2008. The results show that methods with dynamic tie points yields higher estimates. For all the three methods, there is a clear declining trend of multiyear ice area from 1998 to 2008, which is consistent with the decrease of the yearly minimum ice extent. Furthermore, the ice extent of multiyear ice decreases during the winter, reflecting the expected loss of multiyear ice by melt and export to more southern latitudes.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 HEINRICH EVENTS MODELED WITH A COUPLED COMPLEX ICE
SHEET CLIMATE MODEL
We investigate glacial climate variability with a coupled ice sheet model (ISM) atmosphere-ocean-vegetation general circulation model (AOVGCM) system, focusing on one of the most prominent features of glacial climate variability, the Heinrich events. Modeling past climates and periods of past climate change is an important test of the capability of climate models to correctly represent future climate changes. Only if we can correctly represent past climates and climate changes, we can be condent about our predictions of future climate changes. We show results from two experiments: (1) a steady-state LGM experiment where the ice sheet model is accelerated by a factor of 10 compared to the climate model covering 30 kyrs in the ISM (3 kyrs in the AOVGCM) and (2) a synchronously coupled experiment focusing in on one ice sheet collapse covering 3.2 kyrs in both models. For the experiments, we coupled a modified version of the Parallel Ice Sheet Model (mPISM) bidirectionally with the AOVGCM ECHAM5/MPIOM/LPJ. ECHAM5 and LPJ were run in T31 resolution (_ 3:75_), MPIOM on a grid with a nominal resolution of 3_ and poles over Greenland and Antarctica, mPISM on a 20km grid covering most of the northern hemisphere. In the models, as well as in the coupling, no ux correction or anomaly maps are applied. The ice sheet surface mass balance is computed using a positive degree day scheme with lapse rate correction and height desertication ect. In the experiments, the surges of the Hudson Strait Ice Stream reach discharge rates of 60 000m3/s and show a typical recurrence interval of 7 kyrs, matching the basic characteristics for Heinrich events inferred from proxy data. The surges are consequences of an internal instability mechanism suggested by MacAyeal (1993) and various parts of the ice sheets show repeated surging. The large ice discharge during a surge of the Hudson Strait Ice Stream causes an expansion of the sea ice cover in the Labrador Sea and the adjacent North Atlantic. The freshwater, that is released when the ice melts, stabilizes the density stratication in the northern Atlantic. Consequently, the north Atlantic deepwater (NADW) cell weakens by about 10% and the Antarctic BottomWater cell strengthens slightly. The weaker NADW cell transports less heat to the north and thus the ocean heat release decreases. With the increase in sea ice cover and the decrease in ocean heat release, the over the northern Atlantic cools. This cooling spreads downwind into Eurasia. The lower temperature and the increased sea ice cover reduce the evaporation over the northern Atlantic and the Nordic Seas. Consequently, Eurasia receives less precipitation. All in all, the changes in the climate system caused by the ice stream surges are consistent with the proxy reconstructions for Heinrich events.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 COLLECTIVE MOTION IN PENGUIN COLONIES
In Polar Regions, highly adapted social behavior is crucial for the survival of several species. Prominent examples are the huddling behavior of Emperor Penguins, or the crèche (group) formation of King Penguin chicks. To understand how penguins solve the physical problem of movement in densely packed (jammed) groups, we observed Emperor Penguin huddles and King Penguin fledglings with time-lapse/video imaging, and used individual bird tracking and optical flow methods to analyze their movements. We found that Emperor Penguins overcome jamming by moving periodically in large, coordinated clusters. Every 30 - 60 seconds, all penguins make small steps, which travel as a wave through the entire huddle. Over time, these small movements lead to large-scale reorganization of the huddle. Groups of King Penguin fledglings moved in irregular intervals, often attributable to predator attacks, but the individual penguins in the group also moved collectively in a coordinated fashion to ensure the integrity of the group. Our data show that the dynamics of penguin huddling and group formation is governed by intermittency and approach to kinetic arrest in striking analogy with inert non-equilibrium systems. Basic aspects of this behavior can be reproduced with a simple model of interacting point particles.
Individual animals are treated as self-driven agents with situation-dependent behavior, similar to simulations ofcollective swarm behavior in flocks and herds. Both the spontaneous huddle formation and the observed wave patterns emerge from simple rules that only encompass the interaction between directly neighboring individuals. As an important result, our model demonstrates that a collective movement can be triggered by a forward step of any individual within the dense huddle.It remains an open question, however, why individual penguins in a huddle trigger a movement, and by which mechanism the experimentally observed periodicity of huddle movement (~ 40 seconds) remains stable.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 KLIMAWANDEL UND EXTREMEREIGNISSE: INFLUENCE OF
FREEZING PROCESSES ON ORGANIC CONTAMINANT MIGRATION
Arctic regions undergo dramatic changes due to climate change, additionally anthropogenic actions such as mining, exploration and refining increase and cause pollution in arctic soils.
Impact, transport and fate of the contaminants are strongly influenced by the special climatic conditions of the region. If contaminants enter permafrost affected soils they are subjected to repeated freezing and thawing within the active layer. It is hypothesized that due to freezing the distribution of contaminants is affected and a zone of higher contaminant concentrations is developed.
This effect was shown in laboratory column experiments for the water soluble organic contaminant 1-Propanol by (Konrad and Seto, 1991). The underlying processes to create the zone of higher contaminant concentration are water migration and rejection of 1-Propanol during the growth of pore ice, cooling rates smaller than 4°C per day are required for the processes to occur.
The redistribution of raw oil in soil column experiments due to the freezing process was investigated by Chuvilin et al. (2001). For sandy soils it is shown that the oil was rejected and expelled at the freezing front, resulting in low oil contents in the frozen part and elevated oil contents in the unfrozen part right below the freezing front. This part of the column was the one with the lowest freezing rates. Results for fine grained materials such as silt and clay dominated soil materials are not as clear, because two zones of elevated oil contents occur.
Our studies focus on the effect of freeze - thaw cycles on the distribution of hydrophobic organic compounds in soils of different texture. In column experiments the influence of the freezing process on the behavior of the contaminants is investigated. The freezing temperature chosen results in very low freezing rates at the freezing front. First results of these laboratory experiments will be shown and discussed.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 VARIABILITY OF SOIL ORGANIC CARBON STOCKS OF DIFFERENT
PERMAFROST-AFFECTED SOILS: INITIAL RESULTS FROM A
NORTH-SOUTH TRANSECT IN SIBERIA
Twelve sites within a north-south climatological transect in Siberia were investigated to classify the soils and to determine their soil organic carbon stocks in the top 30 cm of the active layer (SSOC-30). There was a distinct arrangement into three groups of increasing SSOC-30 along the transect with decreasing latitude. The greatest SSOC-30, with mean values of 24 ± 9 kg m-2, were identified for the southern group of forest tundra and taiga sites on the ancient Central Siberian Plateau. The soils of the sand-dominated northwestern part of the Lena River Delta, the second river terrace, had a SSOC-30 of only 4 ± 2 kg m-2, whereas the delta’s third and first river terraces stored on average 12 ± 3 kg m-2 in the top 30 cm of the active layer. The climatological gradient with changing vegetation productivity and different parent materials result in varying pedogenetic processes and were identified as key controls on the soil organic carbon stocks.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 ORGANIC CARBON AND TOTAL NITROGEN STOCKS IN SOILS OF
THE LENA RIVER DELTA
The Lena River Delta, which is the largest delta in the Arctic, extends over an area of 32,000 km² and likely holds more than half of the entire soil organic carbon mass stored in the seven major deltas in the northern permafrost regions. The geomorphic units of the Lena River Delta which were formed by true deltaic sedimentation processes are a Holocene river terrace and the active floodplains. Their mean soil organic carbon stocks for the upper 1 m of soils were estimated at 29 kg m-2 ± 10 kg m-2 and at 14 kg m-2 ± 7 kg m-2, respectively. For the depth of 1 m, the total soil organic carbon pool of the Holocene river terrace was estimated at 121 Tg ± 43 Tg, and the soil organic carbon pool of the active floodplains was estimated at 120 Tg ± 66 Tg. The mass of soil organic carbon stored within the observed seasonally thawed active layer was estimated at about 127 Tg assuming an average maximum active layer depth of 50 cm. The soil organic carbon mass which is stored in the perennially frozen ground below 50 cm soil depth, which is excluded from intense biogeochemical exchange with the atmosphere, was estimated at 113 Tg. The mean nitrogen (N) stocks for the upper 1 m of soils were estimated at 1.2 kg m-2 ± 0.4 kg m-2 for the Holocene river terrace and at 0.9 kg m-2 ± 0.4 kg m-2 for the active floodplain levels, respectively. For the depth of 1 m, the total N pool of the river terrace was estimated at 4.8 Tg ± 1.5 Tg, and the total N pool of the floodplains was estimated at 7.7 Tg ± 3.6 Tg. Considering the projections for deepening of the seasonally thawed active layer up to 120 cm in the Lena River Delta region within the 21st century, these large carbon and nitrogen stocks could become increasingly available for decomposition and mineralization processes.
Die "Berichte zur Polar- und Meeresforschung" (ISSN 1866-3192) werden beginnend mit dem Heft Nr. 569 (2008) als Open-Access-Publikation herausgegeben. Ein Verzeichnis aller Hefte einschließlich der Druckausgaben (Heft 377-568) sowie der früheren "Berichte zur Polarforschung" (Heft 1-376, von 1981 bis 2000) befindet sich im open access institutional repository for publications and presentations (ePIC) des AWI unter der URL http://epic.awi.de.
Durch Auswahl "Reports on Polar- and Marine Research" (via "browse"/"type") wird eine Liste der Publikationen sortiert nach Heftnummer innerhalb der absteigenden chronologischen Reihenfolge der Jahrgänge erzeugt.
To generate a list of all Reports past issues, use the following URL: http://epic.awi.de and select "browse"/"type" to browse "Reports on Polar and Marine Research". A chronological list in declining order, issues chronological, will be produced, and pdf-icons shown for open access download.
Verzeichnis der zuletzt erschienenen Hefte:
Heft-Nr. 647/2012 — "The Expedition of the Research Vessel 'Polarstern' to the Arctic in 2011 (ARK-XXVI/1)", edited by Agnieszka Beszczynska-Möller Heft-Nr. 648/2012 — "Interannual and decadal variability of sea ice drift, concentration and thickness in the Weddell Sea", by Sandra Schwegmann Heft-Nr. 649/2012 — "The Expedition of the Research Vessel 'Polarstern' to the Arctic in 2011 (ARK-XXVI/3 - TransArc)", edited by Ursula Schauer Heft-Nr. 650/2012 — "Combining stationary Ocean Models and mean dynamic Topography Data", by Grit Freiwald Heft-Nr. 651/2012 — "Phlorotannins as UV-protective substances in early developmental stages of brown algae", by Franciska S. Steinhoff Heft-Nr. 652/2012 — "The Expedition of the Research Vessel 'Polarstern' to the Antarctic in 2012 (ANT-XXVIII/4)", edited by Magnus Lucassen Heft-Nr. 653/2012 — "Joint Russian-German Polygon Project East Siberia 2011 - 2014: The expedition Kytalyk 2011", edited by Lutz Schirrmeister, Lyudmila Pestryakova, Sebastian Wetterich and Vladimir Tumskoy Heft-Nr. 654/2012 — "The Expedition of the Research Vessel 'Polarstern' to the Antarctic in 2012 (ANT-XXVIII/5)", edited by Karl Bumke Heft-Nr. 655/2012 — "Expeditions to Permafrost 2012: 'Alaskan North Slope / Itkillik', 'Thermokarst in Central Yakutia' and 'EyeSight-NAAT-Alaska', edited by Jens Strauss, Mathias Ulrich and Marcel Buchhorn Heft-Nr. 656/2012 — "The Expedition of the Research Vessel 'Sonne' to the Manihiki Plateau in 2012 (So 224)", edited by Gabriele Uenzelmann-Neben Heft-Nr. 657/2012 — "The Expedition of the Research Vessel 'Polarstern' to the Antarctic in 2011 (ANT-XXVIII/1) ", edited by Saad El Naggar Heft-Nr. 658/2013 — "The Expedition of the Research Vessel 'Polarstern' to the Arctic in 2012 (ARK-XXVII/2) ", edited by Thomas Soltwedel th Heft-Nr. 659/2013 — "Changing Polar Regions - 25 International Congress on Polar Research, March 17-22, 2013, Hamburg, Germany", German Society for Polar Research, edited by Eva-Maria Pfeiffer, Heidemarie Kassens, Mirko Scheinert, Ralf Tiedemann, and Members of the DGP Advisory Board