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«Changing Polar Regions 25th International Congress on Polar Research March 17-22, 2013, Hamburg, Germany German Society for Polar Research Edited by ...»

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This will derive new implications on the Gondwana break-up and further improve our knowledge about the development of landscape contrasts within the Terra Nova Bay region and the interplay between climate, tectonics and lithology.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 SYMBIONT SWITCHING AS AN ADAPTATIONAL STRATEGY OF


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Lichens are symbioses consisting of a fungus (mycobiont) and one or several different algae (photobionts). Cetraria aculeata is a lichen that grows in both polar regions as well as high mountain ranges in between. In addition, it is found in temperate biomes from central Asian steppes to sand-dunes and light forests of western Europe. The species evolved in the northern hemisphere and expanded its range southwards during the Pleistocene. The observation that polar photobionts are genetically more closely related to each other than to temperate ones prompted us to investigate whether the mycobiont can adapt or acclimate to the harsh conditions of polar ecosystems by associating with locally adapted photobionts (photobiont switching). Lichen thalli from temperate and polar regions show different photosynthetic responses. However, molecular genetic data indicates that photobiont switching occurred only rarely over evolutionary time scales. Bayesian Skyline Plots and Stochastic Character Mapping on phylogenetic trees shows that a photobiont switch during the Pleistocene coincided with strong growth of the Mediterranean population. We conclude that algal switching enabled a cold-adapted C. aculeata to colonize temperate biomes, but it does not contribute to acclimation. Instead, transplantation experiments suggest that C. aculeata acclimates by up- and downregulation of photobiont cell numbers. While transplants between polar and dry temperate regions survived two years, transplants between humid and dry regions did not survive the treatment. The potential for acclimation is, hence, limited, but temperature is not the decisive factor. This is also supported by the observation that polar and temperate photobiont cultures show very similar temperature optima.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 COAL SCREE FOUND BURNING IN AUGUST 2011 ON SOUTHERN


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Coal scree of Tertiary Eureka Sound Group coals was found burning on the 24th August 2011 during expedition CASE 12 of the Federal Institute for Geosciences and Natural Resources (Germany) on southern Ellesmere Island. The burning outcrop is located below a steep canyon wall of a small river, which is draining the Prince of Wales Icefield. The river erodes tectonically disturbed coal bearing sediments of the Mount Bell (TMB) and Mount Lawson Formations (TML) of the Eureka Sound Group.

These form scree that obviously was set on fire by spontaneous combustion of the coal pieces, which are scattered all over the talus. The surrounding clasts of claystone and siltstone of the TML/TMB sediments are strongly affected by the heat of the burning coal, i.e. they are pyrometamorphically altered forming all sorts of reddish and beige hard clinker.

Indications for pyrometamorphism related to the spontaneous combustion of coal on Ellesmere Island were previously mentioned for example from the Fosheim Peninsula, where one location is called “clinker” in Dawson et al. (1976). Ricketts (1994) labeled two spots in a section north of Strathcona Fiord with the term “bocanne”, a name specifying “naturally burning shale banks” according to the definition of Crickmay (1967). Recently, Piepjohn et al. (2007) and Estrada et al.

(2009) reported the occurrence of paralava in the Stenkul Fiord and Split Lake areas on southern Ellesmere Island. One coal fire near Split Lake could be dated to have burnt 3.3 ± 0.5 Ma ago in the Middle Pliocene (40Ar-39Ar incremental heating dating on wholerock silicate paralava). At all these localities the coal bearing Eureka Sound Group sediments of Tertiary age crop out over wide areas.

The burning coal scree location gives the possibility to understand in more detail how the widespread occurrences of clinker, i.e. the previous sites of pyrometamorphism, occurring around Strathcona Fiord and Stenkul Fiord were formed.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 CHANGES IN THE ANTARCTIC BOTTOM WATER

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In the last decades, the Antarctic Bottom Water (AABW) warmed and got less dense, and the changes were intensified in the Southern Ocean. Here we use a 27 year long time series of CFC observations in the Weddell Sea to study the changes in ventilation and content of anthropogenic carbon (Cant) in deep and bottom water in the Weddell Sea, the local precursors to AABW. Applying the Transit Time Distribution (TTD) method we find that all deep water masses in the Weddell Sea have been continually growing older and getting less ventilated during the last 27 years. The ventilation rate decline of Weddell Sea Deep and Bottom Water, however, seems to be mainly caused by mixing with Warm Deep Water, which aged much faster. Increasing entrainment of Warm Deep Water or a slowing down of the Weddell Gyre circulation may also play a role. As a consequence of the aging, the Cant increase in the deep and bottom water formed in the Weddell Sea slowed down.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 EVIDENCE FOR RECENT COLONIZATION OF THE AMUNDSEN-SEA


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The Amundsen Sea in the Southern Ocean is amongst the most rapidly changing environments of the world, yet its benthic marine inhabitants are barely known. A new deep-sea isopod crustacean, Macrostylis roaldi, has recently been discovered and described. It is the first new isopod described from the Amundsen-Sea shelf. Its currently known range spreads across 300 km from the inner shelf at Pine Island Bay right to the shelf break as well as bathymetrically across 1,000 m.

Based on DNA barcodes (COI) and additional mitochondrial markers (12S, 16S), a homogenized gene pool across space and depth was detected. This is seen as an indication for a genetic bottleneck and a recent colonization history. Our results suggest further that migratory or dispersal capabilities of some species of brooding macrobenthos have been underestimated. This might be relevant for the species’ potential to cope with effects of climate change. To determine where this species could have survived the last glacial period, alternative refuge possibilities are discussed.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 TWO-WAY COUPLED ICE SHEET-EARTH SYSTEM SIMULATIONS:



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The observed distinct warming in the Arctic and the northward flow of tropical water masses seems to trigger enhanced melting of the Greenland ice sheet, which adds more fresh water into the ambient ocean. A continuation of the observed accelerated/increased melting during the last decade would stabilize the upper column in the adjacent deep water formation sides. With our fully coupled ice sheetearth system we approach the question if this weakens the formation of deep water masses and reduces the oceanic thermohaline driven meridional overturning circulation (MOC). In our two-way fully coupled ice sheet-earth system model system we perform idealized future projections to investigate the response of the interaction under raising atmospheric carbon dioxide (CO2) concentration.

We will present the building blocks of our fully coupled system, which includes a physical based calculation of the ice sheet's surface mass balance and ice sheetocean interaction; The ESM instead is subject to orographic changes and fresh water fluxes, for example. Since the behaviour of an ice sheet in the near future is controlled by both the external forcing and by its initial conditions, we have performed Latin Hyper Cube (LHC) simulations of the ice sheet model PISM over more than one glacial-interglacial cycle utilizing standard techniques to obtain a reasonable initial state. According to several quantities the best performing LHC member is exposed afterwards to boundary conditions determined from energy balance calculations again obtained from simulated forcing fields. Finally the fully coupled system is brought near a quasi equilibrium under pre-industrial conditions before idealized scenarios have been started. In contrast to commonly used strategies, our coupled ice sheet inherits the memory of a glacial cycle simulations obtain exclusively from ESM fields. Furthermore we use a mass conserving scheme, do neither apply flux corrections nor utilize anomaly coupling.

Under different CO2 forcing scenarios -- for example, raising CO2 by 1%/year until four times the pre-industrial concentration (4xCO2) has reached, abrupt raise to 4xCO2 -- the response of the coupled system is analysed. For instance, an abrupt CO2 forcing leads to an immediate response of the Greenlandic ice sheet. The surface mass balance turns strongly negative with a couple of years, causing "Changing Polar Regions" - 25th International Congress on Polar Research 2013 skyrocketing melting rates and sea level rise. The contribution of the ocean-ice sheet interaction decreases instead, because the ice sheets retreats from the coast and is therefore less susceptible to an eroding ocean. The additionally released fresh water and the heat both have to potential to stifle the MOC. However sensitivity experiments indicate that the additional fresh water has a negligible influence on the MOC with a time scale of a century or more in our model system.

For the study we use the current CMIP5 earth system model MPI-ESM that comprises the atmosphere model ECHAM6 (T63Lxx), vegetation model JSBACH and the ocean biogeochemical model MPIOM / HAMOCC (nominal horizontal resolution of 1.5deg with one pole over Greenland). The ESM is coupled to the Parallel Ice Sheet Model (PISM) covering Greenland. PISM has a horizontal resolution 10 km.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 THE GREENLAND ICE SHEET AS AN INTERACTING CLIMATE


Christian Rodehacke, Peter Danish Meteorological Institute (DMI) Langen, Marianne Madsen, Shuting Yang, K. Pagh Nielsen, Jens Christensen Numerous modeling efforts are being performed to describe, in particular, the Greenlandic ice sheet and its interaction with the climate system at the (Danish Climate Center of the) Danish Meteorological Institute. The applications range from a two-way coupled complex global climate-ice sheet model system to spatially high resolution models forecasting the daily surface mass balance over Greenland. These different aspects are covered in comprehensive talk.

Two spatially high resolution atmospheric models (a climate and a weather forecast model) are used in concert to determine the surface mass balance of the Greenland ice sheet. These models provide an up to 10 days forecast of the surface mass balance. The forecast product is offered to the community by the DMI's web site to allow accessing these forecasts during daily field campaigns. The mechanisms, the setup, and the validations of the surface mass balance are presented to the audience. For example the extra ordinary melt event last summer has been reliably forecasted by our system.

The global climate model EC-earth, comprising the ECMWF's atmospheric model IFS and the ocean model NEMO, has been coupled to the Parallel Ice Sheet Model (PISM). We will present the building blocks of our fully coupled system that determines the surface mass balance through a physical based calculation energy balance calculation and includes ice sheet-ocean interaction. The ESM receives, for example, orographic changes and fresh water fluxes from the ice sheet. Before coupling the different pieces together, the ice sheet has be pre-initialized and driven through a glacier-interglacial cycle, so that ice sheet reacts according to the imprinted memory of the glacial-interglacial cycle. Finally, from the fully coupled system, which is in a quasi equilibrium under pre-industrial conditions, idealized scenarios have been started.

Under different idealized CO2 forcing scenarios we present the response of the climate system and in particular the ice sheet of Greenland. A very strong climatic forcing leads to an immediate response of the ice sheet. For example in the most extreme case, where the atmospheric CO2 raises from one day to the next to fourtimes the pre-industrial value, the surface mass balance turns negative within several years. Consequently the ice mass melts and contributes to a raising sea level. The released additional melt water has the potential to reduce the formation of deep waters that drives the global meridional overturning circulation. Sensitivity experiments indicate however that the additional fresh water has a negligible influence.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 RETRIEVING VOLUME CHANGES AND MASS DEPLETION OF


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