ALBERT

Description: Peatlands, wetlands with 〉 30 cm of organic sediment, cover more than 3 x 106 km2 of the earth surface and have been accumulating carbon and sediments throughout the Holocene. The location of peatland formation and accumulation has been dynamic over time, as peat formation in areas like Alaska and the West Siberian Lowlands preceded peat formation in Fennoscandia and Eastern North America due to more favorable climate for peat formation. Using the geographic distribution of peatlands in the past can indicate general climatic conditions, including hydroclimate, given that the underlying geology is well understood. Peatlands form under a variety of climatic conditions and landscape positions but do not persist under arid conditions, instead requiring either humid conditions or cold temperatures. However, peatlands may have existed in the past in areas not currently suitable for peatland formation and persistence, but where peats can be found at depth within the sediment column. Here we map the locations of histic paleosols, relict peat, and buried peats since the Last Glacial Maximum using a compilation of sites from previous studies. We compare these records of past peatland distribution to present-day peatland distribution. We evaluate regional differences in timing of peatland development in these buried peatlands to the development of extant peatlands. Finally, we compare the timing of past peatland extent to the to modeled paleoclimate during the Quaternary. In addition to implications for paleoclimate, these past peatlands are not well accounted for in present-day soil carbon stocks but could be an important component of deep soil carbon pools.

Description: Freshwater ostracods (Crustacea, Ostracoda) are of interest in modern biological studies, while fossil records of ostracod valves enable us to reconstruct past lacustrine environments. The about 1mm long crustaceans carry a calcite carapace that is biomineralized from dissolved components in the ambient water, and completely envelopes their body. Ostracods inhabit almost all aquatic environments, even shallow freshwater ponds in the vast circumartic permafrost areas. In high-latitude areas, ostracod species diversity, their modern ecological demands, and instrumental records of environmental parameters are only scarcely documented. Such reference information is the key to quantitatively reconstruct past environments from fossil ostracod assemblages. This gap in ostracod data limits their use as biological indicators in the Arctic, where the effects of future climate warming are expected to be strongest. The objective of the study presented here was to extend the data set on arctic freshwater ostracods and environmental records by characterizing presentday habitat conditions, abundance and diversity of ostracod assemblages in periglacial freshwaters on Svalbard. The aims of this project were 1. to conduct an inventory of the abundance, diversity and ecological ranges of the freshwater ostracods living in polygon ponds in Adventdalen near Longyearbyen (78°11’11”N, 15°55’20”E), 2. to determine the present-day hydrochemical and sedimentary characteristics of ostracod habitats, and 3. to witness temporal variability in a polygon pond during the Arctic summer season 2013. The study site was located near the University Centre on Svalbard (UNIS)-run monitoring site for thermal contraction cracking in ice-wedge polygons on a river terrace in outer Adventdalen (Christiansen 2005). Permafrost on Svalbard is estimated to be of late Holocene age with temperatures of -5.2 to -5.6 °C in boreholes in the Adventdalen area (Christiansen et al. 2010). Ice-wedge polygons form in cold-climate environments under permafrost conditions and are the most common periglacial patterned ground features in the Arctic (Minke et al. 2007). Since the permafrost table efficiently blocks drainage pathways, surface depressions hold ponding water during summer, and freeze solid in winter. Those shallow periglacial surface freshwaters, called polygon ponds, are hotspots of biological activity in the otherwise hostile tundra. They provide diverse habitats to aquatic communities including freshwater ostracods. For this study, we choose an area with polygon ponds that are known to persist during the summer season. Our sampling scheme of 13 ponds in total comprised collecting freshwater ostracod individuals, pond water and sediment samples. One species, Tonnacypris glacialis (SARS, 1890), was found in only one of the sampled sites, the pond AD-01 (Fig. 1). Continuous water temperature records directly below the water surface in AD-01, and at the sediment surface in about 25cm water depth were collected between July 20 and September 25, 2013. We measured water and thaw depth in the pond centre and the thaw depth of the surrounding polygon rim. The last record at September 25, 2013 completed the observation season with the presence of 2-3cm lake ice. Preliminary results suggest the pond water is welloxygenated and dilute with slightly acidic pH. The hydrochemical fingerprint and sedimentary characteristics of inter- and intrapolygon ponds may allow a differentiation between the two subtypes for the first time, and are subject of ongoing work. Active-layer thickness was around 40-100 cmin polygon rims, we measured about 50-80 cm thaw depth under pond centres. A considerable increase in water surface area extend occurred in the monitored pond after a rain period. The records obtained from this and similar studies in the Siberian Arctic demonstrate that small and shallow periglacial surface waters are sensitive to local permafrost and climate variations. References Christiansen HH. 2005. Thermal regime of icewedge cracking in Adventdalen, Svalbard. Permafrost and Periglacial Processes 16: 87-98. Christiansen HH, Etzelmüller B, Isaksen K, Juliussen H, Farbrot H, Humlum O, Johansson M, Ingeman-Nielsen T, Kristensen L, Hjort J, Holmlund P, Sannel ABK, Sigsgaard C, Åkerman HJ, Foged N, Blikra LH, Pernosky MA, Ødegård RS. 2010. The thermal state of permafrost in the Nordic Area during the International Polar Year 2007–2009. Permafrost and Periglacial Processes 21: 156–181. Minke M, Donner N, Karpov N, de Klerk P, Joosten H. 2007. Distribution, diversity, development and dynamics of polygon mires: examples from Northeast Yakutia (NE Siberia). Peatlands International 1: 36-40.

Description: Glacial−interglacial variations in CO2 and methane in polar ice cores have been attributed, in part, to changes in global wetland extent, but the wetland distribution before the Last Glacial Maximum (LGM, 21 ka to 18 ka) remains virtually unknown. We present a study of global peatland extent and carbon (C) stocks through the last glacial cycle (130 ka to present) using a newly compiled database of 1,063 detailed stratigraphic records of peat deposits buried by mineral sediments, as well as a global peatland model. Quantitative agreement between modeling and observations shows extensive peat accumulation before the LGM in northern latitudes (〉40°N), particularly during warmer periods including the last interglacial (130 ka to 116 ka, MIS 5e) and the interstadial (57 ka to 29 ka, MIS 3). During cooling periods of glacial advance and permafrost formation, the burial of northern peatlands by glaciers and mineral sediments decreased active peatland extent, thickness, and modeled C stocks by 70 to 90% from warmer times. Tropical peatland extent and C stocks show little temporal variation throughout the study period. While the increased burial of northern peats was correlated with cooling periods, the burial of tropical peat was predominately driven by changes in sea level and regional hydrology. Peat burial by mineral sediments represents a mechanism for long-term terrestrial C storage in the Earth system. These results show that northern peatlands accumulate significant C stocks during warmer times, indicating their potential for C sequestration during the warming Anthropocene.