Andre Viau - Academia.edu (original) (raw)
Papers by Andre Viau
R-readable data structure
Matlab-readable data structure
Radiocarbon, 2011
Databases of accumulated paleoecological and archaeological records provide a means for large-sca... more Databases of accumulated paleoecological and archaeological records provide a means for large-scale syntheses of environmental and cultural histories. We describe the current status of the Canadian Archaeological Radiocarbon Database (CARD), a searchable collection of more than 36,000 14C dates from archaeological and paleontological sites from across North America. CARD, built by the late Dr Richard Morlan of the Canadian Museum of Civilization, consists of uncalibrated 14C data as well as information about the material dated, the cultural association of the date (e.g. Paleoindian, Archaic, Woodland), and its geographic location. The database can be used to study questions relating to prehistoric demography, migrations, human vulnerability to environmental change, and human impact on the landscape, but biases relating to sampling intensity and taphonomy must first be accounted for. Currently, Canada and the northern United States are well represented in the database, while the sout...
Quaternary Science Reviews, 2005
Journal of Geophysical Research, 2006
A mean continental July temperature reconstruction based on pollen records from across North Amer... more A mean continental July temperature reconstruction based on pollen records from across North America quantifies temperature variations of several timescales for the past 14,000 cal yr BP. In North America, temperatures increased nearly 4°C during the late glacial, reaching maximum values between 6000 and 3000 cal yr BP, after which mean July temperatures decreased. Superimposed on this orbital-scale trend are millennial-scale temperature variations that appear coherent in structure and frequency with highresolution ice, marine and other terrestrial paleoclimate records of the Holocene. During the Holocene, climate in North America appears to have varied periodically every 1100yearsratherthanthe1100 years rather than the 1100yearsratherthanthe1500 year cycle found during the last glacial period. Coherence at frequencies between 900 and 1100 years between land, ice, and ocean records suggests a common forcing associated with widespread surface impacts during the Holocene. These results provide important insight to the global warming debate, as the observed twentieth century temperature increase appears unprecedented compared to our mean North American temperature reconstruction of the past 14,000 years.
Global Biogeochemical Cycles, 2001
The distribution and abundance of Sphagnum spores in North America and Eurasia are mapped for the... more The distribution and abundance of Sphagnum spores in North America and Eurasia are mapped for the past 21 ka. The present-day distribution of abundant Sphagnum spores corresponds closely to areas with peatland development, with maximum Sphagnum abundance between 630 and 1300 mm annual precipitation and between-2 ø and 6øC mean annual air temperature. During the Wisconsin glaciation, there were apparently not large areas of peatland in North America, except in Alaska. High Sphagnum spore percentages were found in eastern North America during deglaciation. Major peatland development occurred in boreal North America after 9 ka and there was a southward movement of high Sphagnum spore abundance after 5 ka in the western Great Lakes region. Major peatland development began after 9 ka in Europe and Asia. On the basis of maps of the area supporting peatlands, carbon accumulation in peatlands is estimated to be low prior to 11 ka, increased slightly between 11 and 5 ka, and greatly increased during the past 5 ka. ET AL.: SPHAGNUM PEATLANDS SINCE THE LGM 3O9
Paleoclimate inferences from the Canadian Arctic have been hindered by a lack of continuous sedim... more Paleoclimate inferences from the Canadian Arctic have been hindered by a lack of continuous sedimentary sequences, poor chronological control and lack of modern data that are needed for the development of transfer functions or to determine modern analogues. In recent years, a number of lake sediment cores from across the Canadian Arctic have been analyzed, including several sequences from the
Nature Geoscience, Apr 1, 2013
Past global climate changes had strong regional expression. To elucidate their spatio-temporal pa... more Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between AD 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming ...
The Holocene
Paleotempestology, the study of past tropical cyclone activity, has grown considerably over the p... more Paleotempestology, the study of past tropical cyclone activity, has grown considerably over the past two decades, and there is now a relatively dense network of sites across the Western North Atlantic Basin providing records of past tropical cyclone variability. This paper presents a new database of paleotempestological records generated from 61 studies published between 1993 and 2018 for this region. A total of 266 data entries, consisting of the calibrated ages of individual tropical cyclone events and the boundaries of ‘active’ tropical cyclone periods from the present to 8000 cal. yr BP, along with the site names, geographic coordinates, proxy indicator(s) used, materials upon which dating was undertaken, and information about the depositional basin type (e.g. lagoon, mangrove), are included in the database for each site. The database is housed at the National Oceanographic and Atmospheric Association (NOAA) ( https://www.ncdc.noaa.gov/paleo/study/21391 ) and is available for fr...
International Journal of Climatology
Scientific data, Jan 11, 2017
Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing indus... more Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is...
ABSTRACT We reconstructed mean July temperature for the past 30 000 years at Zagoskin Lake (Ager.... more ABSTRACT We reconstructed mean July temperature for the past 30 000 years at Zagoskin Lake (Ager. 2003. Quat Res 60:19) using the Modern Analogue Technique (MAT). Calibration was done using a dataset of 4549 modern pollen samples from across North America, with a pollen sum of 106 pollen taxa. Reconstructed temperatures show a cold full-glacial, warming in the late-glacial and early Holocene and a warm Holocene. Experimentation showed the results are robust with respect to various decisions that can be made in application of the method. Although many of the samples in the full-glacial could be considered non-analogue, the temperatures estimated are reasonable, and comparable to those estimated at samples that are considered analogue. Further, these samples are not greatly deviant when ordinated with modern samples from northern Canada and Alaska.
Journal of Archaeological Science, Mar 31, 2010
Large radiocarbon datasets are increasingly used as a paleodemographic proxy, although potential ... more Large radiocarbon datasets are increasingly used as a paleodemographic proxy, although potential sources of bias in such records are poorly understood. In this paper, we use more than 25,000 radiocarbon dates extracted from the Canadian Archaeological Radiocarbon Database (CARD) to estimate long-term population trends in North America, while critically examining biases in such records. The frequency distribution of CARD dates
![Research paper thumbnail of Comments on: ``The magnitudes of millennial- and orbital-scale climatic change in eastern North America during the Late Quaternary'' by Shuman et al. [Quaternary Science Reviews 24 (2005) 2194 2206]](https://attachments.academia-assets.com/69703948/thumbnails/1.jpg)
](
Many pollen diagrams are available from across Europe documenting the late glacial and postglacia... more Many pollen diagrams are available from across Europe documenting the late glacial and postglacial vegetation succession. Due to the long history of human impact, quantifying the climate history of the region has been problematic. We analysed times of change in European pollen data from the European Pollen Database (EPD). We used a mixture model to fit a series of normal
Agu Fall Meeting Abstracts, Dec 1, 2004
Zagoskin Lake is a 19 m deep maar beyond the limits of late Cenozoic glaciation that contains a 3... more Zagoskin Lake is a 19 m deep maar beyond the limits of late Cenozoic glaciation that contains a 30,000 14C yr B.P. record of climate change. We quantitatively reconstructed the summer thermal regime using midge, diatom, and pollen data. Preliminary inferred mean July air temperatures based on the diatom and midge data show similar trends with LGM temperatures surprisingly similar
Agu Fall Meeting Abstracts, Dec 1, 2010
Future warming is expected to be amplified over high latitudes, especially in winter, but large u... more Future warming is expected to be amplified over high latitudes, especially in winter, but large uncertainties exist in the amount of this polar amplification and the role of feedbacks such as the winter Northern Annular Mode (NAM). Higher temperatures than today also occurred during the peak warming of the present and last Interglacial which could provide possible insight into the main process and feedbacks involved. Large-scale climate reconstructions for these periods have previously focussed mainly on summer season temperatures over high latitudes, and we have so far lacked a clear view of temperature changes in winter, and over lower latitudes against which polar amplification needs to be judged. We have compiled a synthesis of quantitative proxy-temperature reconstructions from across the Northern Hemisphere during the present and last Interglacial for both summer and winter. We find that warming was greater in winter than in summer, and was much stronger over high latitudes relative to lower latitudes. The strength of this polar amplification is not reproduced in climate model simulations, nor is the strength and spatial pattern of winter warming, which appears similar to that experienced under a high index Northern Annular Mode (NAM).
ABSTRACT The Younger Dryas Cool Episode had rapid and widespread effects on flora and fauna throu... more ABSTRACT The Younger Dryas Cool Episode had rapid and widespread effects on flora and fauna throughout the Americas. Fossil pollen records document how plant communities responded to this event, although such data are generally only representative of changes at local- to regional-scales. We use a new approach to provide insight into vegetation responses to the Younger Dryas at a continental-scale, by focusing on data extracted for a single taxon (Populus poplar, cottonwood, aspen) from pollen diagrams throughout North America. We show that Populus underwent a rapid and continent-wide decline as the climate rapidly cooled and dried. At the termination of the Younger Dryas, Populus underwent another widespread decline, this time in response to competition from boreal and temperate taxa as the climate abruptly warmed. Late glacial-early Holocene pollen assemblages with high quantities of Populus pollen often lack modern analogues and thus confound quantitative paleoclimatic reconstructions; our results provide a context to interpret these assemblages. Furthermore, while Populus may continue to expand in the future in response to human disturbance and increasing temperatures, its sensitivity to competition may eventually put it at risk as global warming accelerates.
R-readable data structure
Matlab-readable data structure
Radiocarbon, 2011
Databases of accumulated paleoecological and archaeological records provide a means for large-sca... more Databases of accumulated paleoecological and archaeological records provide a means for large-scale syntheses of environmental and cultural histories. We describe the current status of the Canadian Archaeological Radiocarbon Database (CARD), a searchable collection of more than 36,000 14C dates from archaeological and paleontological sites from across North America. CARD, built by the late Dr Richard Morlan of the Canadian Museum of Civilization, consists of uncalibrated 14C data as well as information about the material dated, the cultural association of the date (e.g. Paleoindian, Archaic, Woodland), and its geographic location. The database can be used to study questions relating to prehistoric demography, migrations, human vulnerability to environmental change, and human impact on the landscape, but biases relating to sampling intensity and taphonomy must first be accounted for. Currently, Canada and the northern United States are well represented in the database, while the sout...
Quaternary Science Reviews, 2005
Journal of Geophysical Research, 2006
A mean continental July temperature reconstruction based on pollen records from across North Amer... more A mean continental July temperature reconstruction based on pollen records from across North America quantifies temperature variations of several timescales for the past 14,000 cal yr BP. In North America, temperatures increased nearly 4°C during the late glacial, reaching maximum values between 6000 and 3000 cal yr BP, after which mean July temperatures decreased. Superimposed on this orbital-scale trend are millennial-scale temperature variations that appear coherent in structure and frequency with highresolution ice, marine and other terrestrial paleoclimate records of the Holocene. During the Holocene, climate in North America appears to have varied periodically every 1100yearsratherthanthe1100 years rather than the 1100yearsratherthanthe1500 year cycle found during the last glacial period. Coherence at frequencies between 900 and 1100 years between land, ice, and ocean records suggests a common forcing associated with widespread surface impacts during the Holocene. These results provide important insight to the global warming debate, as the observed twentieth century temperature increase appears unprecedented compared to our mean North American temperature reconstruction of the past 14,000 years.
Global Biogeochemical Cycles, 2001
The distribution and abundance of Sphagnum spores in North America and Eurasia are mapped for the... more The distribution and abundance of Sphagnum spores in North America and Eurasia are mapped for the past 21 ka. The present-day distribution of abundant Sphagnum spores corresponds closely to areas with peatland development, with maximum Sphagnum abundance between 630 and 1300 mm annual precipitation and between-2 ø and 6øC mean annual air temperature. During the Wisconsin glaciation, there were apparently not large areas of peatland in North America, except in Alaska. High Sphagnum spore percentages were found in eastern North America during deglaciation. Major peatland development occurred in boreal North America after 9 ka and there was a southward movement of high Sphagnum spore abundance after 5 ka in the western Great Lakes region. Major peatland development began after 9 ka in Europe and Asia. On the basis of maps of the area supporting peatlands, carbon accumulation in peatlands is estimated to be low prior to 11 ka, increased slightly between 11 and 5 ka, and greatly increased during the past 5 ka. ET AL.: SPHAGNUM PEATLANDS SINCE THE LGM 3O9
Paleoclimate inferences from the Canadian Arctic have been hindered by a lack of continuous sedim... more Paleoclimate inferences from the Canadian Arctic have been hindered by a lack of continuous sedimentary sequences, poor chronological control and lack of modern data that are needed for the development of transfer functions or to determine modern analogues. In recent years, a number of lake sediment cores from across the Canadian Arctic have been analyzed, including several sequences from the
Nature Geoscience, Apr 1, 2013
Past global climate changes had strong regional expression. To elucidate their spatio-temporal pa... more Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between AD 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming ...
The Holocene
Paleotempestology, the study of past tropical cyclone activity, has grown considerably over the p... more Paleotempestology, the study of past tropical cyclone activity, has grown considerably over the past two decades, and there is now a relatively dense network of sites across the Western North Atlantic Basin providing records of past tropical cyclone variability. This paper presents a new database of paleotempestological records generated from 61 studies published between 1993 and 2018 for this region. A total of 266 data entries, consisting of the calibrated ages of individual tropical cyclone events and the boundaries of ‘active’ tropical cyclone periods from the present to 8000 cal. yr BP, along with the site names, geographic coordinates, proxy indicator(s) used, materials upon which dating was undertaken, and information about the depositional basin type (e.g. lagoon, mangrove), are included in the database for each site. The database is housed at the National Oceanographic and Atmospheric Association (NOAA) ( https://www.ncdc.noaa.gov/paleo/study/21391 ) and is available for fr...
International Journal of Climatology
Scientific data, Jan 11, 2017
Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing indus... more Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is...
ABSTRACT We reconstructed mean July temperature for the past 30 000 years at Zagoskin Lake (Ager.... more ABSTRACT We reconstructed mean July temperature for the past 30 000 years at Zagoskin Lake (Ager. 2003. Quat Res 60:19) using the Modern Analogue Technique (MAT). Calibration was done using a dataset of 4549 modern pollen samples from across North America, with a pollen sum of 106 pollen taxa. Reconstructed temperatures show a cold full-glacial, warming in the late-glacial and early Holocene and a warm Holocene. Experimentation showed the results are robust with respect to various decisions that can be made in application of the method. Although many of the samples in the full-glacial could be considered non-analogue, the temperatures estimated are reasonable, and comparable to those estimated at samples that are considered analogue. Further, these samples are not greatly deviant when ordinated with modern samples from northern Canada and Alaska.
Journal of Archaeological Science, Mar 31, 2010
Large radiocarbon datasets are increasingly used as a paleodemographic proxy, although potential ... more Large radiocarbon datasets are increasingly used as a paleodemographic proxy, although potential sources of bias in such records are poorly understood. In this paper, we use more than 25,000 radiocarbon dates extracted from the Canadian Archaeological Radiocarbon Database (CARD) to estimate long-term population trends in North America, while critically examining biases in such records. The frequency distribution of CARD dates
Many pollen diagrams are available from across Europe documenting the late glacial and postglacia... more Many pollen diagrams are available from across Europe documenting the late glacial and postglacial vegetation succession. Due to the long history of human impact, quantifying the climate history of the region has been problematic. We analysed times of change in European pollen data from the European Pollen Database (EPD). We used a mixture model to fit a series of normal
Agu Fall Meeting Abstracts, Dec 1, 2004
Zagoskin Lake is a 19 m deep maar beyond the limits of late Cenozoic glaciation that contains a 3... more Zagoskin Lake is a 19 m deep maar beyond the limits of late Cenozoic glaciation that contains a 30,000 14C yr B.P. record of climate change. We quantitatively reconstructed the summer thermal regime using midge, diatom, and pollen data. Preliminary inferred mean July air temperatures based on the diatom and midge data show similar trends with LGM temperatures surprisingly similar
Agu Fall Meeting Abstracts, Dec 1, 2010
Future warming is expected to be amplified over high latitudes, especially in winter, but large u... more Future warming is expected to be amplified over high latitudes, especially in winter, but large uncertainties exist in the amount of this polar amplification and the role of feedbacks such as the winter Northern Annular Mode (NAM). Higher temperatures than today also occurred during the peak warming of the present and last Interglacial which could provide possible insight into the main process and feedbacks involved. Large-scale climate reconstructions for these periods have previously focussed mainly on summer season temperatures over high latitudes, and we have so far lacked a clear view of temperature changes in winter, and over lower latitudes against which polar amplification needs to be judged. We have compiled a synthesis of quantitative proxy-temperature reconstructions from across the Northern Hemisphere during the present and last Interglacial for both summer and winter. We find that warming was greater in winter than in summer, and was much stronger over high latitudes relative to lower latitudes. The strength of this polar amplification is not reproduced in climate model simulations, nor is the strength and spatial pattern of winter warming, which appears similar to that experienced under a high index Northern Annular Mode (NAM).
ABSTRACT The Younger Dryas Cool Episode had rapid and widespread effects on flora and fauna throu... more ABSTRACT The Younger Dryas Cool Episode had rapid and widespread effects on flora and fauna throughout the Americas. Fossil pollen records document how plant communities responded to this event, although such data are generally only representative of changes at local- to regional-scales. We use a new approach to provide insight into vegetation responses to the Younger Dryas at a continental-scale, by focusing on data extracted for a single taxon (Populus poplar, cottonwood, aspen) from pollen diagrams throughout North America. We show that Populus underwent a rapid and continent-wide decline as the climate rapidly cooled and dried. At the termination of the Younger Dryas, Populus underwent another widespread decline, this time in response to competition from boreal and temperate taxa as the climate abruptly warmed. Late glacial-early Holocene pollen assemblages with high quantities of Populus pollen often lack modern analogues and thus confound quantitative paleoclimatic reconstructions; our results provide a context to interpret these assemblages. Furthermore, while Populus may continue to expand in the future in response to human disturbance and increasing temperatures, its sensitivity to competition may eventually put it at risk as global warming accelerates.