TOMCAR-PERMAFROST

Terrestrial organic matter characterization in Arctic River through molecular and isotopic analyses

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 Obiettivo del progetto (Objective)

'Climate change is one of the major environmental modifications related to the industrial era. Global warming is not uniform and global climate models project the strongest future warming in the high latitudes. Until now these environments were far less studied than environments at lower latitudes. Most of Arctic rivers drain large permafrost or seasonally frozen areas. The top of the permafrost soils thaws during summer. This active layer plays a crucial role in arctic regions because most ecological, hydrological, biogeochemical and pedogenic activities take place within it. With the expected warming temperature in these regions, the overall area of permafrost is decreasing along with the increasing depth of the active layer. The combination of these two direct consequences of climate change will drastically modify biogeochemical cycles (particularly carbon cycle) of the region. With climate change, and subsequent increasing depth of the active layer, a larger proportion of accumulated soil organic carbon is released to freshwater ecosystems. Beyond organic matter quantities, this last assessment stresses the need of further research on composition and quality of these increasing organic carbon fluxes. Indeed, if most of the organic carbon transferred to the Arctic Ocean is labile and available for degradation, its fate is crucial for biogeochemistry and climate researchers, since it would constitute a positive feedback of climate change through CO2 and CH4 emissions. The object of this research project is to improve our understanding of organic carbon cycle in Arctic River basins, with a particular focus on carbon transfer from soils to rivers based on morphoedaphic characteristics. In order to achieve this goal we decided to work on watersheds with various permafrost influences and with the combination of two complementary tools: Geographic Information System and biogeochemical analysis of river organic carbon (elemental, isotopic and molecular).'

Introduzione (Teaser)

Researchers have shown for the first time how Arctic rivers are transporting vast quantities of organic carbon into the oceans. This process occurs during spring freshet as the permafrost melts.

Descrizione progetto (Article)

Despite the massive impact of climate change on the world's Arctic regions, there is a scarcity of data on exactly how the Arctic regions are changing. In particular, there is little understanding of how spring thawing permafrost is impacting the global carbon cycle.

The EU-funded 'Terrestrial organic matter characterization in Arctic River through molecular and isotopic analyses' (http://www.tomcar.fr (TOMCAR-PERMAFROST)) project is studying the Great Whale River in Canada to understand the effects of permafrost active layer thawing.

Researchers used geographic information systems and biogeochemical analysis to reveal how and what organic carbon is transferred into the oceans by Arctic rivers. They are particularly interested in organic matter composition and quality, as this has a huge effect on carbon cycles.

The project team found that the Great Whale River transported between 200 and 700 tonnes of dissolved organic carbon (DOC) per day during the spring flooding season. This is both old and new DOC, and the composition is influenced by variation in watershed composition due to preferential snow melt related to vegetation cover.

TOMCAR-PERMAFROST also noted that mercury concentration in the River increased three-fold during the flood period. During the project, scientists recorded the highest-ever concentration of dissolved mercury in an Arctic river.

The findings of this project are promising, because such large influxes of DOC into the world's oceans will increase our understanding of the global carbon cycle and thus potential effects on global warming. Then, the information is valuable to researchers trying to model the long-term effects of climate change.