Search for: All records

The Arctic is experiencing warming and ecological shifts due to climate change and the compounding effects of polar amplification. Arctic Alaskan coastal marsh environments, such as the Cape Espenberg barrier beach system, offer an opportunity to determine the carbon cycle response to changing climate by examining sediment records that have been preserved through time as shoreline-parallel, linear geometry prograding geomorphic features. This study determines the carbon and mineral accumulation trends in marsh environments at Cape Espenberg for both paleo (~776 CE to 1850 CE) and modern (post-1850 CE) time frames. A comprehensive physical and chemical dataset, including radioisotope (137Cs, 210Pb, 14C), stable isotope (δ13C), element concentration (%C, %N, C:N), and dry bulk density, has been built for several sediment cores. Results indicate that carbon and mineral accumulation rates have increased from paleo to modern times, potentially because of better growing and preservation conditions for organic matter in a modern climate. Paleoclimate trends in the Medieval Climate Anomaly (MCA) and warm periods interspersed within the Little Ice Age (LIA) also correlate with greater contributions of wetland organic matter, as evidenced by lighter δ13C values. Cold climate periods within the LIA correlate with increased aquatic organic matter sourcing and heavier δ13C values, with some spikes of wetland sources interspersed throughout the LIA. Future temperatures are predicted to rise with global climate change, which may continue to expand carbon stores in Arctic coastal wetland sediments. This has been observed in the swale environments at Cape Espenberg, where increasingly favourable growing and soil-preservation conditions (i.e. wet/anoxic soils and lower salinity to limit organic material decay, higher temperatures to promote growth) are increasing the carbon storage within Arctic coastal carbon reservoirs. 

The Arctic is experiencing warming and ecological shifts due to climate change and the compounded effects of polar amplification. Arctic Alaskan coastal marsh environments, such as the Cape Espenberg barrier beach system, offers an opportunity to determine the carbon cycle response to changing climate in sediment records that have been preserved through time as a shoreline-parallel, linear geometry prograding geomorphic features. This study determines the carbon and mineral accumulation trends in marsh environments at Cape Espenberg for both paleo (pre 1850 after death [AD]) and modern (post 1850 AD) timeframes. A comprehensive physical and chemical dataset, including radioisotope (Caesium-137 [137Cs], Lead-210 [210Pb], Carbon-14 [14C]), stable isotope (delta-13 Carbon [δ13C]), element concentration (%Carbon [C], %Nitrogen [N], C:N), and dry bulk density, has been built for several sediment cores. Results indicate carbon and mineral accumulations have increased from paleo to modern times, potentially due to better growing and/or preservation conditions for organic matter under a modern climate. Paleoclimate trends in the Medieval Climate Anomaly (MCA), and warm periods interspersed within the Little Ice Age (LIA), also correlate to greater contributions of wetland organic matter as evidenced by lighter δ13C values. Cold climate periods within the Little Ice Age correlate with increased aquatic organic matter sourcing and heavier δ13C values with some spikes of wetland sources interspersed throughout the LIA. Modern warming may potentially continue to expand carbon stores in Arctic coastal wetlands as future temperatures are predicted to rise with global climate change, as observed in the swale environments at Cape Espenberg, where increasingly favorable growing and soil preservation conditions (i.e. wet/anoxic soils and lower salinity to limit organic material decay, higher temperatures to promote growth) may result in future Arctic coastal carbon reservoirs. 

The role of high latitude lakes in storing and processing terrestrial organic carbon export is not well understood. We analyzed a 2.7-meter (m) -long sedimentary record from Eight Mile Lake that extends back 15,700 years to evaluate connections between productivity, organic carbon accumulation and late Quaternary environmental change in central Alaska. We analyzed macrofossil radiocarbon, alongside physical and biogeochemical properties. This dataset includes data from 12 sediment cores collected across Eight Mile Lake. These cores span time frames of 1000 - 15,700 years. This dataset includes bulk physical data, organic matter abundance, biogenic silica abundance, particle size, geochronological information, magnetic susceptibility data and hyperspectral imagery. 

The Arctic is experiencing warming and ecological shifts due to climate change and the compounded effects of polar amplification. Arctic Alaskan coastal marsh environments, such as the Cape Espenberg barrier beach system, offers an opportunity to determine the carbon cycle response to changing climate in sediment records that have been preserved through time as a shoreline-parallel, linear geometry prograding geomorphic features. This study determines the carbon and mineral accumulation trends in marsh environments at Cape Espenberg for both paleo (pre 1850 after death [AD]) and modern (post 1850 AD) timeframes. A comprehensive physical and chemical dataset, including radioisotope (Caesium-137 [137Cs], Lead-210 [210Pb], Carbon-14 [14C]), stable isotope (delta-13 Carbon [δ13C]), element concentration (%Carbon [C], %Nitrogen [N], C:N), and dry bulk density, has been built for several sediment cores. Results indicate carbon and mineral accumulations have increased from paleo to modern times, potentially due to better growing and/or preservation conditions for organic matter under a modern climate. Paleoclimate trends in the Medieval Climate Anomaly (MCA), and warm periods interspersed within the Little Ice Age (LIA), also correlate to greater contributions of wetland organic matter as evidenced by lighter δ13C values. Cold climate periods within the Little Ice Age correlate with increased aquatic organic matter sourcing and heavier δ13C values with some spikes of wetland sources interspersed throughout the LIA. Modern warming may potentially continue to expand carbon stores in Arctic coastal wetlands as future temperatures are predicted to rise with global climate change, as observed in the swale environments at Cape Espenberg, where increasingly favorable growing and soil preservation conditions (i.e. wet/anoxic soils and lower salinity to limit organic material decay, higher temperatures to promote growth) may result in future Arctic coastal carbon reservoirs. 

Recent excavation in the new CRREL Permafrost Tunnel in Fox, Alaska provides a unique opportunity to study properties of Yedoma — late Pleistocene ice- and organic-rich syngenetic permafrost. Yedoma has been described at numerous sites across Interior Alaska, mainly within the Yukon-Tanana upland. The most comprehensive data on the structure and properties of Yedoma in this area have been obtained in the CRREL Permafrost Tunnel near Fairbanks — one of the most accessible large-scale exposures of Yedoma permafrost on Earth, which became available to researchers in the mid-1960s. Expansion of the new ∼4-m-high and ∼4-m-wide linear excavations, started in 2011 and ongoing, exposes an additional 300 m of well-preserved Yedoma and provides access to sediments deposited over the past 40,000 years, which will allow us to quantify rates and patterns of formation of syngenetic permafrost, depositional history and biogeochemical characteristics of Yedoma, and its response to a warmer climate. In this paper, we present results of detailed cryostratigraphic studies in the Tunnel and adjacent area. Data from our study include ground-ice content, the stable water isotope composition of the variety of ground-ice bodies, and radiocarbon age dates. Based on cryostratigraphic mapping of the Tunnel and results of drilling above and inside the Tunnel, six main cryostratigraphic units have been distinguished: 1) active layer; 2) modern intermediate layer (ice-rich silt); 3) relatively ice-poor Yedoma silt reworked by thermal erosion and thermokarst during the Holocene; 4) ice-rich late Pleistocene Yedoma silt with large ice wedges; 5) relatively ice-poor fluvial gravel; and 6) ice-poor bedrock. Our studies reveal significant differences in cryostratigraphy of the new and old CRREL Permafrost Tunnel facilities. Original syngenetic permafrost in the new Tunnel has been better preserved and less affected by erosional events during the period of Yedoma formation, although numerous features (e.g., bodies of thermokarst-cave ice, thaw unconformities, buried gullies) indicate the original Yedoma silt in the recently excavated sections was also reworked to some extent by thermokarst and thermal erosion during the late Pleistocene and Holocene.