Dissolved organic carbon (DOC) in Arctic ground ice, from northwest Canada, east Siberia, and Alaska

Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have accumulated in late Pleistocene and Holocene unconsolidated deposits. Permafrost vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change are largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements which are important for ecosystems and carbon cycling. Here we show, using biogeochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage, with a maximum of 28.6 mg/L (mean: 9.6 mg/L). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly frozen and stored in ground ice, especially in ice wedges, even before further degradation. We found that ice wedges in the Yedoma region represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a freshwater reservoir of 4200 km**3. This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost carbon pool for ecosystems and climate feedback upon mobilization.

El reclamo territorial Ayoreo Totobiegosode. En: Avá, nº 14

El proceso jurídico-administrativo abierto en 1993 ante los poderes del Estado Paraguayo para la reivindicación de una parte del territorio de los Totobiegosode, grupo local del pueblo Ayoreo, es experiencia singular en el país. En el proceso, los instrumentos jurídicos que garantizan derechos de los pueblos indígenas están sometidos a prueba no sólo en lo relativo a la coherencia de sus postulados, disposiciones y procedimientos, sino también en función a las constricciones del contexto socio-político. El trabajo expone el abordaje interdisciplinario de la gestión conjunta entre los Ayoreo Totobiegosode y profesionales no indígenas, como las distintas dimensiones administradas en la reivindicación territorial: étnica, ambiental, patrimonial cultural y de derechos humanos. La existencia de sub-grupos Totobiegosode sin contacto con la sociedad envolvente, y la transformación acelerada de la región del Chaco Paraguayo, son condiciones particulares de los trámites aún en curso.