Glen M Macdonald
Dados Biográficos
| ID | 3608217 |
|---|---|
| NOME | Glen M Macdonald |
| PRENOMES | Glen M |
| SOBRENOME | Macdonald |
| ASSINATURA | MACDONALD G M |
| AFILIAÇÕES | University of California, Los Angeles |
| ORCID | 0000-0002-0267-9825 |
| VERIFICADO | Sim |
| TOTAL DE OBRAS | 46 |
| TOTAL DE CITAÇÕES | 50 |
| TOTAL COMO AUTOR | 46 |
| TOTAL COMO EDITOR | 0 |
| PRIMEIRO ANO DE PUBLICAÇÃO | 1980 |
| ANO MAIS RECENTE DE PUBLICAÇÃO | 2026 |
| ÍNDICE H | 4 |
Reconstructing 32,000 years of hydrologic variability through an elemental geochemistry lake depth transfer function at Lake Elsinore, California
Lake sediments record past hydrologic variability, but natural lakes are often sparse in semiarid and arid regions, making the calibration of paleohydrologic models a challenge. At Lake Elsinore, the largest of the few natural lakes in Southern California, we explore and develop a novel transfer function approach for reconstructing lake depth. Using 32 modern surface sediment samples spanning Lake Elsinore’s littoral to profundal zones, we establ…
Global Wildfire
Wildfires have been an integral part of Earth's ecology for over 400 million years, and impact many terrestrial ecosystems at present. Wildfires provide habitat diversity and promote biodiversity, but can be costly to humans in terms of destroyed infrastructure and loss of life. Global mapping of annual wildfires by satellite remote sensing suggests that ∼200 to ∼500 Mha of land‐surface burn annually. Highest amounts of annual area burned are typ…
Drought-vulnerable vegetation increases exposure of disadvantaged populations to heatwaves under global warming
Climate Change
"Climate Change: Geography’s Debt and Geography’s Dilemma." The Professional Geographer, 74(1), pp. 137–138
High-resolution sedimentological and geochemical records of three marshes in San Francisco Bay, California
Climate and growing season variability impacted the intensity and distribution of Fremont maize farmers during and after the Medieval Climate Anomaly based on a statistically downscaled climate model
The rise and decline of many complex, pre-European maize-farming cultures in the American Southwest coincides with the warm, climatically quiescent Medieval Climate Anomaly (MCA, ca. 850–1350 CE) and transition to the cool, hydrologically variable Little Ice Age (LIA, ca. 1350–1850 CE). The effects of drought on early subsistence agriculture in the Southwest is well studied, but the impact of temperature stress and variability on the growth of ma…
Climate, Capital, Conflict
Anthropogenic climate change will disproportionately affect equatorial regions and closely adjacent areas, referred to here as the Fateful Ellipse. The vulnerability of these regions is exacerbated by a lack of capital for adaptive measures against the impacts of climate change. The increasing transference of capital from governmental control to private hands, and the increasing concentration of such capital into the hands of fewer individuals ra…
Simulated impact of paleoclimate change on Fremont Native American maize farming in Utah, 850–1449 CE, using crop and climate models
The Fremont were members of an expansive maize-based Ancestral Puebloan (AP) cultural complex who disappeared from Utah between the 12th and 13th centuries CE. This period brackets that of a climatic transition in the Southwest from the warm, dry Medieval Climate Anomaly (MCA, ca. 850–1350 CE) to the cool, hydro-climatically variable Little Ice Age (LIA, ca. 1350–1850 CE). We simulated maize (Zea mays) crop productivity for Fremont AP archaeologi…
The new nature
Paleoenvironmental research is an important component of biogeography. The profound environmental changes wrought by human activity over the past 300 years challenge the previous focus on past “natural” systems and the use of past environmental conditions to anticipate future anthropogenic environmental changes. In many cases, due to profound environmental changes brought on by humans, the past may not be the key to the present nor the future. Je…
Marine Radiocarbon Reservoir Values in Southern California Estuaries
Many studies use radiocarbon dates on estuarine shell material to build age-depth models of sediment accumulation in estuaries in California, USA. Marine 14 C ages are typically older than dates from contemporaneous terrestrial carbon and local offsets (ΔR) from the global average marine offset need to be calculated to ensure the accuracy of calibrated dates. We used accelerator mass spectrometry (AMS) 14 C dating on 40 pre-1950 salt marsh snail …
A 2000-yr reconstruction of air temperature in the Great Basin of the United States with specific reference to the Medieval Climatic Anomaly
A sediment core representing the past two millennia was recovered from Stella Lake in the Snake Range of the central Great Basin in Nevada. The core was analyzed for sub-fossil chironomids and sediment organic content. A quantitative reconstruction of mean July air temperature (MJAT) was developed using a regional training set and a chironomid-based WA-PLS inference model (r 2 jack = 0.55, RMSEP = 0.9°C). The chironomid-based MJAT reconstruction …
Long-term successional changes in peatlands of the Hudson Bay Lowlands, Canada inferred from the ecological dynamics of multiple proxies
Peatlands in northern Ontario, Canada, archive multiple biological indicators, including macrofossils, algae, testate amoebae, and pollen. These proxies can provide insights concerning the timing and nature of long-term climatic and environmental changes. The Hudson Bay Lowlands (HBL) of central Canada contain one of Earth’s largest continuous peatland complexes, and thus comprehensive spatial and temporal studies are needed to understand the imp…
Peatland succession and long-term apparent carbon accumulation in central and northern Ontario, Canada
Despite their importance as globally significant carbon (C) stores, basic knowledge of post-glacial peatland history and C accumulation are lacking for the Canadian Boreal Shield and James Bay Lowland (JBL) of central and northern Ontario, Canada. Radiocarbon dates, plant macrofossil analysis, and soil C estimates from an eight-core transect of the JBL and surrounding regions are used to reconstruct the timings and patterns of fen to bog transiti…
A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation
Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45°N. It encompasses regions within which peat carbon data have only recently become available, such as the West Siberia Lowlands, the Hudson Bay Lowlands, Kamchatka in Far East Russia, and the Tibetan…
A Dynamic History of Climate Change and Human Impact on the Environment from Keālia Pond, Maui, Hawaiian Islands
High-resolution palynological, charcoal, and sedimentological analysis of a sediment core from Keālia Pond, Maui, coupled with archaeological and historical records, provides a detailed chronology of vegetation and climate change since before human arrival. These records provide new evidence for human–environment linkages during the Hawaiian Polynesian period and subsequent European period. Prior to human arrival, the charcoal record indicates th…
Recent Warming Reverses Long-Term Arctic Cooling
Climate Reversal The climate and environment of the Arctic have changed drastically over the short course of modern observation. Kaufman et al. (p. 1236 ) synthesized 2000 years of proxy data from lakes above 60° N latitude with complementary ice core and tree ring records, to create a paleoclimate reconstruction for the Arctic with a 10-year resolution. A gradual cooling trend at the start of the record had reversed by the beginning of the 20th …
Climatic and hydrologic variability during the past millennium in the eastern Rocky Mountains and northern Great Plains of western Canada
Modelling of tree-ring δ 13 C and δ 18 O data from the Columbia Icefield area in the eastern Rocky Mountains of western Canada provides fuller understanding of climatic and hydrologic variability over the past 1000 yr in this region, based on reconstruction of changes in growth season atmospheric relative humidity ( RH grs ), winter temperature ( T win ) and the precipitation δ 18 O– T win relation. The Little Ice Age (~ AD 1530s–1890s) is marked…
Evidence of temperature depression and hydrological variations in the eastern Sierra Nevada during the Younger Dryas Stade
Sediment records from two lakes in the east-central Sierra Nevada, California, provide evidence of cooling and hydrological shifts during the Younger Dryas stade (YD; ~ 12,900–11,500 cal yr BP). A chironomid transfer function suggests that lake-water temperatures were depressed by 2°C to 4°C relative to maximum temperatures during the preceding Bølling–Allerød interstade (BA; ~ 14,500–12,900 cal yr BP). Diatom and stable isotope records suggest d…
Late-Quaternary summer temperature changes in the northern-European tree-line region
We present two new quantitative July mean temperature (T jul ) reconstructions from the Arctic tree-line region in the Kola Peninsula in north-western Russia. The reconstructions are based on fossil pollen records and cover the Younger Dryas stadial and the Holocene. The inferred temperatures are less reliable during the Younger Dryas because of the poorer fit between the fossil pollen samples and the modern samples in the calibration set than du…
Southern California and the perfect drought
The 22nd Pacific Climate Workshop (Paclim)
Severe and sustained drought in southern California and the West
A late Quaternary chironomid-inferred temperature record from the Sierra Nevada, California, with connections to northeast Pacific sea surface temperatures
Chironomid remains from a mid-elevation lake in the Sierra Nevada, California, were used to estimate quantitative summer surface water temperatures during the past ∼15,000 yr. Reconstructed temperatures increased by ∼3°C between lake initiation and the onset of the Holocene at ∼10,600 cal yr BP (calibrated years before present). Temperatures peaked at 6500 cal yr BP, displayed high variability from 6500 to 3500 cal yr BP, and stabilized after 350…
Disappearing Arctic Lakes
Historical archived satellite images were compared with contemporary satellite data to track ongoing changes in more than 10,000 large lakes in rapidly warming Siberia. A widespread decline in lake abundance and area has occurred since 1973, despite slight precipitation increases to the region. The spatial pattern of lake disappearance suggests (i) that thaw and "breaching" of permafrost is driving the observed losses, by enabling rapid lake drai…
Quantitative reconstruction of Holocene climate from the Chuna Lake pollen record, Kola Peninsula, northwest Russia
July mean temperatures and annual precipitation during the last 9000 years were inferred using the pollen record from Chuna Lake, Kola Peninsula, Russia. A quantitative pollen-climate model was generated using the best modem analogues method from a training set of 99 surface pollen spectra from the Kola Peninsula, northern Fennoscandia and Karelia. According to the evidence from Chuna Lake, the early and mid-Holocene (c. 9000-5000 cal. BP) was wa…
A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation
Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45°N. It encompasses regions within which peat carbon data have only recently become available, such as the West Siberia Lowlands, the Hudson Bay Lowlands, Kamchatka in Far East Russia, and the Tibetan…
Marine Radiocarbon Reservoir Values in Southern California Estuaries
Many studies use radiocarbon dates on estuarine shell material to build age-depth models of sediment accumulation in estuaries in California, USA. Marine 14 C ages are typically older than dates from contemporaneous terrestrial carbon and local offsets (ΔR) from the global average marine offset need to be calculated to ensure the accuracy of calibrated dates. We used accelerator mass spectrometry (AMS) 14 C dating on 40 pre-1950 salt marsh snail …
Response of the Central Canadian Treeline to Recent Climatic Changes
Dendrochronology and the analysis of historical records from eighteenth, nineteenth, and early twentieth-century expeditions are used to reconstruct the response of the central Canadian treeline to recent climatic variations. Cold summer temperatures during the early to mid-nineteenth century contributed to low rates of growth and poor recruitment of white and black spruce at treeline. Despite the harsh conditions, however, individuals of both sp…
Radiocarbon dated Pinus sylvestris L. wood from beyond tree-line on the Kola Peninsula, Russia
Radiocarbon dates were obtained from 24 samples of Pinus sylvestris L. (Scots pine) wood recovered from sites beyond the modern conifer tree-line on the Kola Peninsula of Russia. Twenty-one of the samples came from the shallow waters and eroding peats at the edges of two small lakes at 68°439N, 35°109E, located north of the modern conifer tree-line. Three samples came from a small pond located above the modern elevational limits of Pinus sylvestr…
Climate, Capital, Conflict
Anthropogenic climate change will disproportionately affect equatorial regions and closely adjacent areas, referred to here as the Fateful Ellipse. The vulnerability of these regions is exacerbated by a lack of capital for adaptive measures against the impacts of climate change. The increasing transference of capital from governmental control to private hands, and the increasing concentration of such capital into the hands of fewer individuals ra…
Effect of varying oceanicity on early- to mid-Holocene palaeohydrology, Kola Peninsula, Russia
The stable-isotope stratigraphy of sedimentary organic matter and algal cellulose in cores from two lakes near treeline on the Kola Peninsula indicate changes in water and nutrient balance that correlate with inferred expansion of Pinus sylvestris during the early to mid-Holocene. Trends in cellulose-inferred lakewater δ 18 O values for both lakes suggest that moist conditions after deglaciation were followed by progressive drying from about 9500…
Tree-ring and summer-temperature response to volcanic aerosol forcing at the northern tree-line, Kola Peninsula, Russia
Potential linkages between volcanic activity and a 403-year record of Pinus sylvestris L. (Scots pine) growth and summer temperatures estimated from tree-ring widths are evaluated from an Arctic tree-line site on the Kola Peninsula, northwestern Russia. The joint occurrence of volcanic eruptions and severe negative ring-width values is more than four times that expected by chance. A composite average of temperatures indicates that a 0.72°C temper…
The new nature
Paleoenvironmental research is an important component of biogeography. The profound environmental changes wrought by human activity over the past 300 years challenge the previous focus on past “natural” systems and the use of past environmental conditions to anticipate future anthropogenic environmental changes. In many cases, due to profound environmental changes brought on by humans, the past may not be the key to the present nor the future. Je…
Long-term successional changes in peatlands of the Hudson Bay Lowlands, Canada inferred from the ecological dynamics of multiple proxies
Peatlands in northern Ontario, Canada, archive multiple biological indicators, including macrofossils, algae, testate amoebae, and pollen. These proxies can provide insights concerning the timing and nature of long-term climatic and environmental changes. The Hudson Bay Lowlands (HBL) of central Canada contain one of Earth’s largest continuous peatland complexes, and thus comprehensive spatial and temporal studies are needed to understand the imp…
Peatland succession and long-term apparent carbon accumulation in central and northern Ontario, Canada
Despite their importance as globally significant carbon (C) stores, basic knowledge of post-glacial peatland history and C accumulation are lacking for the Canadian Boreal Shield and James Bay Lowland (JBL) of central and northern Ontario, Canada. Radiocarbon dates, plant macrofossil analysis, and soil C estimates from an eight-core transect of the JBL and surrounding regions are used to reconstruct the timings and patterns of fen to bog transiti…
A Dynamic History of Climate Change and Human Impact on the Environment from Keālia Pond, Maui, Hawaiian Islands
High-resolution palynological, charcoal, and sedimentological analysis of a sediment core from Keālia Pond, Maui, coupled with archaeological and historical records, provides a detailed chronology of vegetation and climate change since before human arrival. These records provide new evidence for human–environment linkages during the Hawaiian Polynesian period and subsequent European period. Prior to human arrival, the charcoal record indicates th…
Quantitative reconstruction of Holocene climate from the Chuna Lake pollen record, Kola Peninsula, northwest Russia
July mean temperatures and annual precipitation during the last 9000 years were inferred using the pollen record from Chuna Lake, Kola Peninsula, Russia. A quantitative pollen-climate model was generated using the best modem analogues method from a training set of 99 surface pollen spectra from the Kola Peninsula, northern Fennoscandia and Karelia. According to the evidence from Chuna Lake, the early and mid-Holocene (c. 9000-5000 cal. BP) was wa…
Rocky Mountain Alluvial Fans
Movement of an Ice-Cored Rock Glacier, Tungsten, N.W.T., Canada, 1963-1980
In August 1963 Dr. H. Gabrielse, of the Geological Survey of Canada, established five lines of marked boulders on what is now believed to be a large ice-cored rock glacier near Tungsten, Northwest Territories. The boulders were aligned with survey targets located on the rock walls of the valley in which the rock glacier is located. The distances from the snout of the rock glacier to eight forest trees along its perimeter were measured and blazed …
Postglacial Vegetation History of the Mackenzie River Basin
Three radiocarbon-dated cores from small lakes provide pollen records of postglacial vegetation change in the central Mackenzie River basin. These data are combined with previously published records to reconstruct vegetation development from central Alberta to the Mackenzie delta. The paleoecological data demonstrate that a continuous corridor of herb-and-shrub-dominated vegetation extended between Beringia and the Great Plains of North America f…
Rocky Mountain Alluvial Fans
Holocene Vegetation Change at Treeline North of Yellowknife, Northwest Territories, Canada
Two radiocarbon-dated cores from small lakes located approximately 25 km north of the mapped boundary between forest-tundra and tundra provide records of postglacial vegetation change at the treeline near Yellowknife, NWT, Canada. Basal radiocarbon dates of 6180 and 7470 yr B.P. were obtained from the cores. The fossil pollen evidence suggests that the initial vegetation was Betula tundra with a peatland component. Alnus became an important const…
The reconstruction of boreal forest fire history from lake sediments
Carbon Isotope Composition of Lake Sediments in Relation to Lake Productivity and Radiocarbon Dating
Carbon-13 profiles and radiocarbon dates were obtained from two Canadian kettle basins having similar geological and hydrological characteristics to develop criteria for evaluating the validity of radiocarbon dates on lake sediment from basins in calcareous terrain. Radiocarbon dates from a site in Alberta show a variable hard-water effect related to local hydrological changes during postglacial history of the lake basin, whereas radiocarbon date…
Dendroclimatic Reconstruction of Summer Temperatures in Northwestern Canada since A.D. 1638 Based on Age-Dependent Modeling
Ring widths from five Picea glauca stands at the alpine treeline in northwestern Canada are used to investigate climate-growth responses and to develop a long reconstruction of summer temperatures. Response function and linear regression analyses indicate that the radial growth response of these trees to climate varies with age and site. At most sites, the period of significant positive response to growing season temperatures declines with tree a…
A Dendroclimatic Reconstruction of Annual Precipitation on the Western Canadian Prairies since A.D. 1505 from Pinus flexilis James
Tree-ring chronologies from living and sub-fossil Pinus flexilis James (limber pine) trees extend back more than 500 yr on the western edge of the Great Plains in Alberta. Living trees were found to be as old as 526 yr. Tree-ring growth in Pinus flexilis is most sensitive to annual precipitation over the annualization period August to July. The longevity of the trees coupled with their sensitivity to variations in annual precipitation make them a…
Influence of Changing Atmospheric Circulation on Precipitation δ 18 O–Temperature Relations in Canada during the Holocene
Postglacial precipitation δ 18 O history has been reconstructed for two regions of Canada. Long-term shifts in the oxygen-isotope composition of annual precipitation (δ 18 O p ) in southern Ontario appear to have occurred with a consistent isotope–temperature relation throughout the past 11,500 14 C yr. The modern isotope–temperature relation in central Canada near present boreal treeline evidently became established between 5000 and 4000 years a…
The Holocene closing of the ‘ice-free’ corridor
A 930-year ring-width chronology from moisture-sensitive white spruce (Picea glauca Moench) in northwestern Canada
A 930-year tree-ring chronology was constructed from living and subfossil white spruce ( Picea glauca Moench) from the Campbell Dolomite Upland, Northwest Territories, Canada. Response function analy sis using climate data from nearby Inuvik indicates that 69% of the variation in ring widths can be explained by monthly precipitation and temperature. Ring width is most strongly correlated with high precipitation between February and May. There is …
Arctic Environmental Change of the Last Four Centuries
A compilation of paleoclimate records from lake sediments, trees, glaciers, and marine sediments provides a view of circum-Arctic environmental variability over the last 400 years. From 1840 to the mid-20th century, the Arctic warmed to the highest temperatures in four centuries. This warming ended the Little Ice Age in the Arctic and has caused retreats of glaciers, melting of permafrost and sea ice, and alteration of terrestrial and lake ecosys…
Response of the Central Canadian Treeline to Recent Climatic Changes
Dendrochronology and the analysis of historical records from eighteenth, nineteenth, and early twentieth-century expeditions are used to reconstruct the response of the central Canadian treeline to recent climatic variations. Cold summer temperatures during the early to mid-nineteenth century contributed to low rates of growth and poor recruitment of white and black spruce at treeline. Despite the harsh conditions, however, individuals of both sp…
Holocene Paleohydrology and Paleoclimate at Treeline, North-Central Russia, Inferred from Oxygen Isotope Records in Lake Sediment Cellulose
Lake-water oxygen-isotope histories for three lakes in northern Russia, derived from the cellulose oxygen-isotope stratigraphies of sediment cores, provide the basis for preliminary reconstruction of Holocene paleohydrology in two regions along the boreal treeline. Deconvolution of shifting precipitation δ 18 O from secondary evaporative isotopic enrichment is aided by knowledge of the distribution of isotopes in modern precipitation, the isotopi…
Holocene Treeline History and Climate Change Across Northern Eurasia
Radiocarbon-dated macrofossils are used to document Holocene treeline history across northern Russia (including Siberia). Boreal forest development in this region commenced by 10,000 yr B.P. Over most of Russia, forest advanced to or near the current arctic coastline between 9000 and 7000 yr B.P. and retreated to its present position by between 4000 and 3000 yr B.P. Forest establishment and retreat was roughly synchronous across most of northern …
Biological evidence of multiple temporal and spatial scales of hydrological variation in the western interior of Canada
Radiocarbon dated Pinus sylvestris L. wood from beyond tree-line on the Kola Peninsula, Russia
Radiocarbon dates were obtained from 24 samples of Pinus sylvestris L. (Scots pine) wood recovered from sites beyond the modern conifer tree-line on the Kola Peninsula of Russia. Twenty-one of the samples came from the shallow waters and eroding peats at the edges of two small lakes at 68°439N, 35°109E, located north of the modern conifer tree-line. Three samples came from a small pond located above the modern elevational limits of Pinus sylvestr…
Tree-ring and summer-temperature response to volcanic aerosol forcing at the northern tree-line, Kola Peninsula, Russia
Potential linkages between volcanic activity and a 403-year record of Pinus sylvestris L. (Scots pine) growth and summer temperatures estimated from tree-ring widths are evaluated from an Arctic tree-line site on the Kola Peninsula, northwestern Russia. The joint occurrence of volcanic eruptions and severe negative ring-width values is more than four times that expected by chance. A composite average of temperatures indicates that a 0.72°C temper…
Effect of varying oceanicity on early- to mid-Holocene palaeohydrology, Kola Peninsula, Russia
The stable-isotope stratigraphy of sedimentary organic matter and algal cellulose in cores from two lakes near treeline on the Kola Peninsula indicate changes in water and nutrient balance that correlate with inferred expansion of Pinus sylvestris during the early to mid-Holocene. Trends in cellulose-inferred lakewater δ 18 O values for both lakes suggest that moist conditions after deglaciation were followed by progressive drying from about 9500…
Holocene thermal maximum in the western Arctic (0–180°W)
Holocene vegetation history and climate change on the northern Kola Peninsula, Russia
Disappearing Arctic Lakes
Historical archived satellite images were compared with contemporary satellite data to track ongoing changes in more than 10,000 large lakes in rapidly warming Siberia. A widespread decline in lake abundance and area has occurred since 1973, despite slight precipitation increases to the region. The spatial pattern of lake disappearance suggests (i) that thaw and "breaching" of permafrost is driving the observed losses, by enabling rapid lake drai…
Quantitative reconstruction of Holocene climate from the Chuna Lake pollen record, Kola Peninsula, northwest Russia
July mean temperatures and annual precipitation during the last 9000 years were inferred using the pollen record from Chuna Lake, Kola Peninsula, Russia. A quantitative pollen-climate model was generated using the best modem analogues method from a training set of 99 surface pollen spectra from the Kola Peninsula, northern Fennoscandia and Karelia. According to the evidence from Chuna Lake, the early and mid-Holocene (c. 9000-5000 cal. BP) was wa…
A late Quaternary chironomid-inferred temperature record from the Sierra Nevada, California, with connections to northeast Pacific sea surface temperatures
Chironomid remains from a mid-elevation lake in the Sierra Nevada, California, were used to estimate quantitative summer surface water temperatures during the past ∼15,000 yr. Reconstructed temperatures increased by ∼3°C between lake initiation and the onset of the Holocene at ∼10,600 cal yr BP (calibrated years before present). Temperatures peaked at 6500 cal yr BP, displayed high variability from 6500 to 3500 cal yr BP, and stabilized after 350…
Severe and sustained drought in southern California and the West
Geography (40 obras) · Geology and Paleoclimatology Research (37 obras) · Physical geography (36 obras) · Climate change (26 obras) · Climatology (24 obras) · Holocene (23 obras) · Geology (21 obras) · Geology (21 obras) · Oceanography (18 obras) · Environmental Science (17 obras)