Los retornos del exilio en Argentina y Uruguay : Una historia comparada de las políticas y tensiones en la recepción y asistencia en las posdictaduras (1983-1989)

Fil: Lastra, Soledad. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

(Table 1) Gas tie points used to correlate the ice cores NGRIP and EDML

Water isotope records from the EPICA Dronning Maud Land (EDML) and the NorthGRIP ice cores have revealed a one to one coupling between Antarctic Isotope Maxima (AIM) and Greenland Dansgaard-Oeschger (DO) events back to 50 kyr. In order to explore if this north-south coupling is persistent over Marine Isotopic Stage 5 (MIS 5), a common timescale must first be constructed. Here, we present new records of d18O of O2 (d18Oatm) and methane (CH4) measured in the air trapped in ice from the EDML (68-147 kyr) and NorthGRIP (70-123 kyr) ice cores. We demonstrate that, through the period of interest, CH4 records alone are not sufficient to construct a common gas timescale between the two cores. Millennial-scale variations of d18Oatm are evidenced over MIS 5 both on the Antarctic and Greenland ice cores and are coupled to CH4 profiles to synchronise the NorthGRIP and EDML records. They are shown to be a precious tool for ice core synchronisation. With this new dating strategy, we produce the first continuous and accurate sequence of the north-south climatic dynamics on a common ice timescale for the last glacial inception and the first DO events of MIS 5, reducing relative dating uncertainties to an accuracy of a few centuries at the onset of DO events 24 to 20. This EDML-NorthGRIP synchronisation provides new firm evidence that the bipolar seesaw is a pervasive pattern from the beginning of the glacial period. The relationship between Antarctic warming amplitudes and their concurrent Greenland stadial duration highlights the particularity of DO event 21 and its Antarctic counterpart. Our results suggest a smaller Southern Ocean warming rate for this long DO event compared to DO events of MIS 3.

Proglacial river dataset from the Akuliarusiarsuup Kuua River northern tributary, Southwest Greenland, 2008 - 2013, version 2.0

The dataset contains measurements of river stage and discharge for one sites along the Akuliarusiarsuup Kuua River's northern tributary, with 30 minute temporal resolution between June 2008 and August 2013 This river is a tributary to the Watson River discharging into Kangerlussuaq Fjord by the town of Kangerlussuaq, Southwest Greenland. Additional data of water temperature, air pressure are also provided. Compared to version 1.0 of the dataset, this dataset used a total of 36 in situ discharge observations collected between 2008 and 2012 to construct the rating curve. Furthermore, data of Station AK-004-001 between 2010-09-06T11:30 to 2010-09-07T13:30 have been removed from version 2.0 because these values were likely caused by backflow when a jokulhlaup from a large glacier dammed lake caused increased water levels in the downstreams lake. Thus, data measured at AK-004-001 between 2010-09-06T11:30 to 2010-09-07T13:30 are not representative for the AK-004 catchment.

Data from the EPICA Dome C ice core EDC

The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago (Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long - 28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.

Rates of seropositivity for Toxoplasma gondii antibodies in polar bears and marine mammals around Svalbard

Little is known about the prevalence of the parasite Toxoplasma gondii in the arctic marine food chain of Svalbard, Norway. In this study, plasma samples were analyzed for T. gondii antibodies using a direct agglutination test. Antibody prevalence was 45.6% among polar bears (Ursus maritimus), 18.7% among ringed seals (Pusa hispida) and 66.7% among adult bearded seals (Erignathus barbatus) from Svalbard, but no sign of antibodies were found in bearded seal pups, harbour seals (Phoca vitulina), white whales (Delphinapterus leucas) or narwhals (Monodon monoceros) from the same area. Prevalence was significantly higher in male polar bears (52.3%) compared with females (39.3%), likely due to dietary differences between the sexes. Compared to an earlier study, T. gondii prevalence in polar bears has doubled in the past decade. Consistently, an earlier study on ringed seals did not detect T. gondii. The high recent prevalence in polar bears, ringed seals and bearded seals could be caused by an increase in the number or survivorship of oocysts being transported via the North Atlantic Current to Svalbard from southern latitudes. Warmer water temperatures have led to influxes of temperate marine invertebrate filter-feeders that could be vectors for oocysts and warmer water is also likely to favour higher survivorship of oocycts. However, a more diverse than normal array of migratory birds in the Archipelago recently, as well as a marked increase in cruise-ship and other human traffic are also potential sources of T. gondii.

Maps and acoustic profiles of free gas distribution, Western Baltic Sea and Kattgat-Skagerrak area

A shallow gas depth-contour map covering the Skagerrak-western Baltic Sea region has been constructed using a relatively dense grid of existing shallow seismic lines. The digital map is stored as an ESRI shape file in order to facilitate comparison with other data from the region. Free gas usually occurs in mud and sandy mud but is observed only when sediment thickness exceeds a certain threshold value, depending on the water depth of the area in question. Gassy sediments exist at all water depths from approx. 20 m in the coastal waters of the Kattegat to 360 m in the Skagerrak. In spite of the large difference in water depths, the depth of free gas below seabed varies only little within the region, indicating a relatively fast movement of methane in the gas phase towards the seabed compared to the rate of diffusion of dissolved methane. Seeps of old microbial methane occur in the northern Kattegat where a relatively thin cover of sandy sediments exists over shallow, glacially deformed Pleistocene marine sediments. Previous estimates of total methane escape from the area may be correct but the extrapolation of local methane seepage rate data to much larger areas on the continental shelf is probably not justified. Preliminary data on porewater chemistry were compared with the free gas depth contours in the Aarhus Bay area, which occasionally suffers from oxygen deficiency, in order to examine if acoustic gas mapping may be used for monitoring the condition of the bay.