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Locating Cryptotephra In Sediments Using Fluid Imaging Technology, Robert D'Anjou, Nicholas L. Balascio, Raymond S. Bradley
Locating Cryptotephra In Sediments Using Fluid Imaging Technology, Robert D'Anjou, Nicholas L. Balascio, Raymond S. Bradley
Raymond S Bradley
We report a new approach to locate and quantify cryptotephra in sedimentary archives using a continuously-imaging Flow Cytometer and Microscope (FlowCAM_). The FlowCAM rapidly photographs particles flowing in suspension past a microscope lens and performs semi-automated analysis of particle images. It has had primarily biological applications, although the potential sedimentological applications are numerous. Here we test the ability of this instrument to image irregularly shaped, vesicular glass shards and to screen sediment samples for the presence of cryptotephra. First, reference samples of basalt and rhyolite tephra (sieved <63>microns) were analyzed with the FlowCAM, demonstrating the ability of the instrument to …
Biogeochemical Evidence For Hydrologic Change During The Holocene In A Lake Sediment Record From Southeast Greenland, Nicholas L. Balascio, William J. D'Andrea, Raymond S. Bradley, Bianca B. Perren
Biogeochemical Evidence For Hydrologic Change During The Holocene In A Lake Sediment Record From Southeast Greenland, Nicholas L. Balascio, William J. D'Andrea, Raymond S. Bradley, Bianca B. Perren
Raymond S Bradley
Holocene paleoclimate records from Greenland help us understand the response of the Greenland Ice Sheet and regional oceanic and atmospheric circulation systems to natural climate variability in order to place recent changes in a longer-term perspective. Here biogeochemical analysis of a lake sediment core from southeast Greenland is used to define changes in moisture balance and runoff during the Holocene in a catchment near the margin of the Greenland Ice Sheet. A 1.6 m sediment core that spans the last 8.8 ka was recovered from Flower Valley Lake on Ammassalik Island. Magnetic susceptibility, diatoms, bulk biogeochemical properties (TOC, C/N, δ13Corg), …
Evaluating Holocene Climate Change In Northern Norway Using Sediment Records From Two Contrasting Lake Systems., Nicholas L. Balascio, Raymond S. Bradley
Evaluating Holocene Climate Change In Northern Norway Using Sediment Records From Two Contrasting Lake Systems., Nicholas L. Balascio, Raymond S. Bradley
Raymond S Bradley
We analyzed Holocene sedimentary records from two lakes in the Lofoten Islands, northern Norway to evaluate environmental changes during the Holocene related to northern North Atlantic climate dynamics. The lakes are located in different geomorphological settings, and thus provide a contrast in their response to regional climate change. Environmental changes at both lakes were interpreted based on magnetic susceptibility, organic-matter flux, C/N, d13 Corg , Ti concentrations, and mass accumulation rates. Chronologies were established using 16 AMS radiocarbon dates, and average deposition rates in both environments are higher than 0.2 mm/year throughout the Holocene. At Vikjordvatnet, sedimentary geochemical properties define …
Biogeochemical Evidence For Prehistoric Human Impacts On The Environment In Northwestern Norway, Raymond S. Bradley, Robert D'Anjou, Nicholas L. Balascio, David B. Finkelstein
Biogeochemical Evidence For Prehistoric Human Impacts On The Environment In Northwestern Norway, Raymond S. Bradley, Robert D'Anjou, Nicholas L. Balascio, David B. Finkelstein
Raymond S Bradley
Disentangling the effects of climate change and anthropogenic activities on the environment is a major challenge in paleoenvironmental research. Here, we used fecal sterols and other biogeochemical compounds in lake sediments from northern Norway to identify both natural and anthropogenic signals of environmental change during the late Holocene. The area was first occupied by humans and their grazing animals at ∼2,250 ± 75 calendar years before 1950 AD (calendar years before present). The arrival of humans is indicated by an abrupt increase in coprostanol (and its epimer epicoprostanol) in the sediments and an associated increase in 5β-stigmastanol (and 5β-epistigmastanol), which …
A Mild Little Ice Age And Unprecedented Warmth In An 1800 Year Record From Svalbard, William J. D'Andrea, Raymond S. Bradley, David Vaillencourt, Nicholas L. Balascio, Al Werner, Steve Roof, Michael J. Retelle
A Mild Little Ice Age And Unprecedented Warmth In An 1800 Year Record From Svalbard, William J. D'Andrea, Raymond S. Bradley, David Vaillencourt, Nicholas L. Balascio, Al Werner, Steve Roof, Michael J. Retelle
Raymond S Bradley
The Arctic region is subject to a great amplitude of climate variability and is currently undergoing large-scale changes due in part to anthropogenic global warming. Accurate projections of future change depend on anticipating the response of the Arctic climate system to forcing, and understanding how the response to human forcing will interact with natural climate variations. The Svalbard Archipelago occupies an important location for studying patterns and causes of Arctic climate variability; however, available paleoclimate records from Svalbard are of restricted use due to limitations of existing climate proxies. Here we present a sub-decadal- to multidecadal-scale record of summer temperature …
Natural Archives, Changing Climates, Raymond S. Bradley
Natural Archives, Changing Climates, Raymond S. Bradley
Raymond S Bradley
Climatic changes have occurred throughout human history, but instrumental measurements do not provide us with a very long perspective on climate variations. In many regions, instrumental records only extend back a century or two. To understand the longer-term variability of the climate system, we rely on natural archives— sediments, ice caps, peat bogs, cave deposits, banded corals and tree rings—in which a record of past changes in climate has been preserved. They are a treasure trove of the climatic and environmental history of the planet and provide information about factors that may have caused the climate to change, such as …
A Multi-Proxy Approach To Assessing Isolation Basin Stratigraphy From The Lofoten Islands, Norway, Nicholas L. Balascio, Zhaohui Zhang, Raymond S. Bradley, Bianca B. Perren, Svein-Olaf Dahl, Jostein Bakke
A Multi-Proxy Approach To Assessing Isolation Basin Stratigraphy From The Lofoten Islands, Norway, Nicholas L. Balascio, Zhaohui Zhang, Raymond S. Bradley, Bianca B. Perren, Svein-Olaf Dahl, Jostein Bakke
Raymond S Bradley
This study takes a comprehensive approach to characterizing the isolation sequence of Heimerdalsvatnet, a coastal lake in the Lofoten Islands, northern Norway. We use established methods and explore new techniques to assess changes in marine influence. Bathymetric and sub-bottom profiles were acquired to examine basin-wide sedimentation and a 5.8 m sediment core spanning the last 7800 cal yr BP was analyzed. We measured magnetic susceptibility, bulk organic matter properties, molecular biomarkers, diatom assemblages, and elemental profiles acquired by scanning X-ray fluorescence. These characteristics of the sediment reflect detailed changes in salinity and water column conditions as the lake was progressively …