Human-environmental interactions in the Arctic inferred from microfossils in Central Greenland ice

Abstract:

Temperatures in high latitudes are icreasing twice as fast as the global mean, which affect sensitive Arctic ecosystems. Microfossil impurities such as microcharcoal particles in surface snow on the Greenland ice sheet directly change the surface albedo, potentially contributing to accelerating climate change. Over time, these microfossil particles are incorporated into growing layers of ice thereby preserving records of past environmental changes over millennia. Recent methodological advances permit extraction of these microfossils from remote polar ice cores in sufficient numbers to achieve continuous environmental records. Such palynological analyses provide new insights into the long-term and large-scale vegetation, fire, and pollution dynamics in the Arctic region. We use pollen and spores in ice cores to infer past vegetation composition and land use, microscopic charcoal for biomass burning, and SCP (=spheroidal carbonaceous particles) as a specific tracer for fossil fuel burning.

We present results from the high-elevation Summit Eurocore’89 site in Central Greenland and the lower-elevation Act11d site in Southern Greenland. Our pollen data suggest that microfossil sources vary substantially across the Greenland ice sheet with the southern lower-elevation site containing larger shares from the boreal conifer forest, while the Central Greenland site further north primarily reflects subarctic shrublands and tundra. These empirical results are consistent with FLEXPART aerosol transport model simulations for the individual sites. We infer that human activities in the 20^th century such as coal burning and sheep herding heavily impacted sensitive Arctic ecosystems. We present optical palynology as a powerful novel tool for paleoecological reconstructions in these unique and extremely remote ice archives located hundreds of kilometers from potential microfossil sources. Our study provides essential knowledge transferable to other remote microfossil records from glaciers in the mid-latitudes and the tropics.