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Clarke Knight, PhD (Former Employee)

Science and Products

Sediment cores collected in Guatemala

Drivers and Impacts of North Pacific Climate Variability

Climate model forecasts indicate an increase in extreme hydrologic events, including floods and droughts, for California and the western U.S. in the future. To better understand what the consequences of this future change in climate may be, USGS scientists are studying the frequency, magnitude, and impacts of past hydroclimate variability and extremes in the region. This project produces well...
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center
Drivers and Impacts of North Pacific Climate Variability

Drivers and Impacts of North Pacific Climate Variability

Climate model forecasts indicate an increase in extreme hydrologic events, including floods and droughts, for California and the western U.S. in the future. To better understand what the consequences of this future change in climate may be, USGS scientists are studying the frequency, magnitude, and impacts of past hydroclimate variability and extremes in the region. This project produces well...
Learn More

​Geochemical, grain size, lithological, diatom, bathymetric, and age model data for Wildcat Lake, Point Reyes National Seashore 2021 ​Geochemical, grain size, lithological, diatom, bathymetric, and age model data for Wildcat Lake, Point Reyes National Seashore 2021

These data are the geochemical (from X-ray fluorescence spectrometry), grain size, lithological (loss on ignition), diatom assemblages (taxa counts), bathymetric, and radioactive isotopes (210-Pb, 137Cs) from sediments from Wildcat Lake, Point Reyes National Seashore, California, USA starting in 2021. Taken together, they provide evidence for extreme precipitation events linked to...
By
Ecosystems Land Change Science Program, California Water Science Center

Geochemical, grain size, lithological, bathymetric, reconstructed integrated vapor transport, and age model data for Leonard Lake, Mendocino County Geochemical, grain size, lithological, bathymetric, reconstructed integrated vapor transport, and age model data for Leonard Lake, Mendocino County

The data herein are geochemical (from X-Ray fluorescence spectrometry), grain size (percent clay, silt, sand), lithological (loss on ignition data), bathymetric, reconstructed IVT, and radioactive isotopes (14-C, 210-Pb, 226-Ra, and 137-Cs). These data were collected from sediments from Leonard Lake, Mendocino County, California, USA starting in 2014. Together, these data provide...
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center

Pollen data from seven lakes in the Klamath Mountains, California: a case study for paleoecological reconstruction Pollen data from seven lakes in the Klamath Mountains, California: a case study for paleoecological reconstruction

The dataset include raw pollen counts, age model data, and pollen accumulation rates with uncertainty estimates for seven lake sites in the Klamath Mountains, California, USA. The raw pollen counts reflect the relative abundance of major taxa from the vegetation surrounding each lake site (n=7) at 5 different time periods. The age model data provides a Bayesian-based estimate of the...
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center
Douglas-fir forest in northwestern California
Douglas-fir Forest in the Klamath Bioregion of California
Douglas-fir Forest in the Klamath Bioregion of California
Douglas-fir forest in northwestern California

Douglas-fir Forest in the Klamath Bioregion of California

Douglas-fir Forest in the Klamath Bioregion of California

Dense stands of Douglas-fir surround South Twin Lake in the Klamath bioregion of northwestern California.

By
Climate Research and Development Program
Douglas-fir forest in northwestern California

Douglas-fir Forest in the Klamath Bioregion of California

Douglas-fir Forest in the Klamath Bioregion of California

Dense stands of Douglas-fir surround South Twin Lake in the Klamath bioregion of northwestern California.

By
Climate Research and Development Program

Guidelines for producing integrated 210Pb and 14C age-models Guidelines for producing integrated 210Pb and 14C age-models

Accurate reconstructions of past environmental changes are crucial in paleoecological research and require reliable chronologies of sedimentary archives. Establishing robust age-models and obtaining the most appropriate proxies for analysis is a complex scientific endeavor, requiring extensive resources and collaboration among specialists, including radiochronologists. Radiometric dating...
Authors
Joan-Albert Sanchez-Cabeza, Marco Aquino-López, Maarten Blaauw, Ana Ruiz-Fernández, Johanna Jupin, Lysanna Anderson, Clarke Knight, Marie Champagne, Nicole Sanderson, Simon Goring, J. Christen
By
Geology, Minerals, Energy, and Geophysics Science Center

Leveraging wildfire to augment forest management and amplify forest resilience Leveraging wildfire to augment forest management and amplify forest resilience

Successive catastrophic wildfire seasons in western North America have escalated the urgency around reducing fire risk to communities and ecosystems. In historically frequent-fire forests, fuel buildup as a result of fire exclusion is contributing to increased fire severity. The probability of high-severity fire can be reduced by active forest management that reduces fuels, prompting...
Authors
Kristen I. Shive, Clarke Knight, Zachary Steel, Charlotte K. Stanley, Kristen N. Wilson
By
Geology, Minerals, Energy, and Geophysics Science Center

Twentieth century extreme precipitation detected in a high-resolution, coastal lake-sediment record from California Twentieth century extreme precipitation detected in a high-resolution, coastal lake-sediment record from California

California faces increasing economic and societal risks from extreme precipitation and flooding associated with atmospheric rivers (ARs) under projected twenty-first century climate warming. Lake sediments can retain signals of past extreme precipitation events, allowing reconstructions beyond the period of instrumental records. Here, we calibrate AR-related extreme precipitation from...
Authors
Clarke Knight, David Wahl, Jason Addison, Mark Baskaran, R. Scott Anderson, Marie Champagne, Lysanna Anderson, Liubov Presnetsova, Beth Caissie, Scott Starratt
By
Geology, Minerals, Energy, and Geophysics Science Center

Atmospheric river activity during the late Holocene exceeds modern range of variability in California Atmospheric river activity during the late Holocene exceeds modern range of variability in California

Atmospheric rivers are associated with some of the largest flood-producing precipitation events in western North America, particularly California. Insight into past extreme precipitation can be reconstructed from sedimentary archives on millennial timescales. Here we document atmospheric river activity near Leonard Lake, California, over 3,200 years, using a key metric of atmospheric...
Authors
Clarke Knight, Lysanna Anderson, Liubov Presnetsova, Marie Champagne, David Wahl
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center

Methods for robust estimates of tree biomass from pollen accumulation rates: Quantifying paleoecological reconstruction uncertainty Methods for robust estimates of tree biomass from pollen accumulation rates: Quantifying paleoecological reconstruction uncertainty

Pollen accumulation rates (PAR, grains cm–2 year–1) have been shown to be a reliable but methodologically complex bioproxy for quantitative reconstruction of past tree abundance. In a prior study, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus, and the pollen group TC (Taxaceae and Cupressaceae families) – were robust and precise estimators of...
Authors
Clarke Knight, John Battles, M. Bunting, Marie Champagne, James Wanket, David Wahl
By
Geology, Minerals, Energy, and Geophysics Science Center

Land management explains major trends in forest structure and composition over the last millennium in California’s Klamath Mountains Land management explains major trends in forest structure and composition over the last millennium in California’s Klamath Mountains

For millennia, forest ecosystems in California have been shaped by fire from both natural processes and Indigenous land management, but the notion of climatic variation as a primary controller of the pre-colonial landscape remains pervasive. Understanding the relative influence of climate and Indigenous burning on the fire regime is key because contemporary forest policy and management...
Authors
Clarke Knight, Lysanna Anderson, M. Bunting, Marie Champagne, Rosie Clayburn, Jeffrey Crawford, Anna Klimaszewski-Patterson, Eric Knapp, Frank Lake, Scott Mensing, David Wahl, James Wanket, Alex Watts-Tobin, Matthew Potts, John Battles
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center

Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA

Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm−2 year−1) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments...
Authors
Clarke Knight, Mark Baskaran, M. Bunting, Marie Champagne, Matthew Potts, David Wahl, James Wanket, John Battles
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center

Sierra Nevada summary report. California’s Fourth Climate Change Assessment Sierra Nevada summary report. California’s Fourth Climate Change Assessment

The Sierra Nevada region is critical to the environment and economy of California. Its places and peoples provideessential natural resources including fresh water, clean power, working lands, and famous wilderness. The regionencompasses tremendous geographical, climatological, and ecological diversity that spans majestic mountains todeep desert basins. The climate consists of cool, wet...
Authors
Michael Dettinger, Holly Alpert, John Battles, Jonathan Kusel, Hugh Safford, Dorian Fougeres, Clarke Knight, Lauren Miller, Sarah Sawyer
By
Water Resources Mission Area
Long-term Atmospheric River History in California

Long-term Atmospheric River History in California

Reconstructing patterns of extreme precipitation beyond the instrumental record to help managers be better prepared for what is possible.

Read Article
Friday's Findings - May 19 2023

Friday's Findings - May 19 2023

Title: Historical Role of Fire in the Klamath Mountains, California

Speaker: Clarke Knight, PhD, Postdoctoral Researcher, USGS Geology, Minerals...

Read Article
Innovative Paleoclimate Methods

Innovative Paleoclimate Methods

The Land Change Science Program in the USGS Ecosystems Mission Area (EMA) covers a tremendous breadth of topics important to understanding how climate...

Read Article
Indigenous management helped shape northern California forests for over 1000 years

Indigenous management helped shape northern California forests for over 1000 years

This article is part of the Spring 2022 issue of the Earth Science Matters Newsletter.

Read Article

Science and Products

Sediment cores collected in Guatemala

Drivers and Impacts of North Pacific Climate Variability

Climate model forecasts indicate an increase in extreme hydrologic events, including floods and droughts, for California and the western U.S. in the future. To better understand what the consequences of this future change in climate may be, USGS scientists are studying the frequency, magnitude, and impacts of past hydroclimate variability and extremes in the region. This project produces well...
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center
Drivers and Impacts of North Pacific Climate Variability

Drivers and Impacts of North Pacific Climate Variability

Climate model forecasts indicate an increase in extreme hydrologic events, including floods and droughts, for California and the western U.S. in the future. To better understand what the consequences of this future change in climate may be, USGS scientists are studying the frequency, magnitude, and impacts of past hydroclimate variability and extremes in the region. This project produces well...
Learn More

​Geochemical, grain size, lithological, diatom, bathymetric, and age model data for Wildcat Lake, Point Reyes National Seashore 2021 ​Geochemical, grain size, lithological, diatom, bathymetric, and age model data for Wildcat Lake, Point Reyes National Seashore 2021

These data are the geochemical (from X-ray fluorescence spectrometry), grain size, lithological (loss on ignition), diatom assemblages (taxa counts), bathymetric, and radioactive isotopes (210-Pb, 137Cs) from sediments from Wildcat Lake, Point Reyes National Seashore, California, USA starting in 2021. Taken together, they provide evidence for extreme precipitation events linked to...
By
Ecosystems Land Change Science Program, California Water Science Center

Geochemical, grain size, lithological, bathymetric, reconstructed integrated vapor transport, and age model data for Leonard Lake, Mendocino County Geochemical, grain size, lithological, bathymetric, reconstructed integrated vapor transport, and age model data for Leonard Lake, Mendocino County

The data herein are geochemical (from X-Ray fluorescence spectrometry), grain size (percent clay, silt, sand), lithological (loss on ignition data), bathymetric, reconstructed IVT, and radioactive isotopes (14-C, 210-Pb, 226-Ra, and 137-Cs). These data were collected from sediments from Leonard Lake, Mendocino County, California, USA starting in 2014. Together, these data provide...
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center

Pollen data from seven lakes in the Klamath Mountains, California: a case study for paleoecological reconstruction Pollen data from seven lakes in the Klamath Mountains, California: a case study for paleoecological reconstruction

The dataset include raw pollen counts, age model data, and pollen accumulation rates with uncertainty estimates for seven lake sites in the Klamath Mountains, California, USA. The raw pollen counts reflect the relative abundance of major taxa from the vegetation surrounding each lake site (n=7) at 5 different time periods. The age model data provides a Bayesian-based estimate of the...
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center
Douglas-fir forest in northwestern California
Douglas-fir Forest in the Klamath Bioregion of California
Douglas-fir Forest in the Klamath Bioregion of California
Douglas-fir forest in northwestern California

Douglas-fir Forest in the Klamath Bioregion of California

Douglas-fir Forest in the Klamath Bioregion of California

Dense stands of Douglas-fir surround South Twin Lake in the Klamath bioregion of northwestern California.

By
Climate Research and Development Program
Douglas-fir forest in northwestern California

Douglas-fir Forest in the Klamath Bioregion of California

Douglas-fir Forest in the Klamath Bioregion of California

Dense stands of Douglas-fir surround South Twin Lake in the Klamath bioregion of northwestern California.

By
Climate Research and Development Program

Guidelines for producing integrated 210Pb and 14C age-models Guidelines for producing integrated 210Pb and 14C age-models

Accurate reconstructions of past environmental changes are crucial in paleoecological research and require reliable chronologies of sedimentary archives. Establishing robust age-models and obtaining the most appropriate proxies for analysis is a complex scientific endeavor, requiring extensive resources and collaboration among specialists, including radiochronologists. Radiometric dating...
Authors
Joan-Albert Sanchez-Cabeza, Marco Aquino-López, Maarten Blaauw, Ana Ruiz-Fernández, Johanna Jupin, Lysanna Anderson, Clarke Knight, Marie Champagne, Nicole Sanderson, Simon Goring, J. Christen
By
Geology, Minerals, Energy, and Geophysics Science Center

Leveraging wildfire to augment forest management and amplify forest resilience Leveraging wildfire to augment forest management and amplify forest resilience

Successive catastrophic wildfire seasons in western North America have escalated the urgency around reducing fire risk to communities and ecosystems. In historically frequent-fire forests, fuel buildup as a result of fire exclusion is contributing to increased fire severity. The probability of high-severity fire can be reduced by active forest management that reduces fuels, prompting...
Authors
Kristen I. Shive, Clarke Knight, Zachary Steel, Charlotte K. Stanley, Kristen N. Wilson
By
Geology, Minerals, Energy, and Geophysics Science Center

Twentieth century extreme precipitation detected in a high-resolution, coastal lake-sediment record from California Twentieth century extreme precipitation detected in a high-resolution, coastal lake-sediment record from California

California faces increasing economic and societal risks from extreme precipitation and flooding associated with atmospheric rivers (ARs) under projected twenty-first century climate warming. Lake sediments can retain signals of past extreme precipitation events, allowing reconstructions beyond the period of instrumental records. Here, we calibrate AR-related extreme precipitation from...
Authors
Clarke Knight, David Wahl, Jason Addison, Mark Baskaran, R. Scott Anderson, Marie Champagne, Lysanna Anderson, Liubov Presnetsova, Beth Caissie, Scott Starratt
By
Geology, Minerals, Energy, and Geophysics Science Center

Atmospheric river activity during the late Holocene exceeds modern range of variability in California Atmospheric river activity during the late Holocene exceeds modern range of variability in California

Atmospheric rivers are associated with some of the largest flood-producing precipitation events in western North America, particularly California. Insight into past extreme precipitation can be reconstructed from sedimentary archives on millennial timescales. Here we document atmospheric river activity near Leonard Lake, California, over 3,200 years, using a key metric of atmospheric...
Authors
Clarke Knight, Lysanna Anderson, Liubov Presnetsova, Marie Champagne, David Wahl
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center

Methods for robust estimates of tree biomass from pollen accumulation rates: Quantifying paleoecological reconstruction uncertainty Methods for robust estimates of tree biomass from pollen accumulation rates: Quantifying paleoecological reconstruction uncertainty

Pollen accumulation rates (PAR, grains cm–2 year–1) have been shown to be a reliable but methodologically complex bioproxy for quantitative reconstruction of past tree abundance. In a prior study, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus, and the pollen group TC (Taxaceae and Cupressaceae families) – were robust and precise estimators of...
Authors
Clarke Knight, John Battles, M. Bunting, Marie Champagne, James Wanket, David Wahl
By
Geology, Minerals, Energy, and Geophysics Science Center

Land management explains major trends in forest structure and composition over the last millennium in California’s Klamath Mountains Land management explains major trends in forest structure and composition over the last millennium in California’s Klamath Mountains

For millennia, forest ecosystems in California have been shaped by fire from both natural processes and Indigenous land management, but the notion of climatic variation as a primary controller of the pre-colonial landscape remains pervasive. Understanding the relative influence of climate and Indigenous burning on the fire regime is key because contemporary forest policy and management...
Authors
Clarke Knight, Lysanna Anderson, M. Bunting, Marie Champagne, Rosie Clayburn, Jeffrey Crawford, Anna Klimaszewski-Patterson, Eric Knapp, Frank Lake, Scott Mensing, David Wahl, James Wanket, Alex Watts-Tobin, Matthew Potts, John Battles
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center

Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA

Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm−2 year−1) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments...
Authors
Clarke Knight, Mark Baskaran, M. Bunting, Marie Champagne, Matthew Potts, David Wahl, James Wanket, John Battles
By
Ecosystems Land Change Science Program, Geology, Minerals, Energy, and Geophysics Science Center

Sierra Nevada summary report. California’s Fourth Climate Change Assessment Sierra Nevada summary report. California’s Fourth Climate Change Assessment

The Sierra Nevada region is critical to the environment and economy of California. Its places and peoples provideessential natural resources including fresh water, clean power, working lands, and famous wilderness. The regionencompasses tremendous geographical, climatological, and ecological diversity that spans majestic mountains todeep desert basins. The climate consists of cool, wet...
Authors
Michael Dettinger, Holly Alpert, John Battles, Jonathan Kusel, Hugh Safford, Dorian Fougeres, Clarke Knight, Lauren Miller, Sarah Sawyer
By
Water Resources Mission Area
Long-term Atmospheric River History in California

Long-term Atmospheric River History in California

Reconstructing patterns of extreme precipitation beyond the instrumental record to help managers be better prepared for what is possible.

Read Article
Friday's Findings - May 19 2023

Friday's Findings - May 19 2023

Title: Historical Role of Fire in the Klamath Mountains, California

Speaker: Clarke Knight, PhD, Postdoctoral Researcher, USGS Geology, Minerals...

Read Article
Innovative Paleoclimate Methods

Innovative Paleoclimate Methods

The Land Change Science Program in the USGS Ecosystems Mission Area (EMA) covers a tremendous breadth of topics important to understanding how climate...

Read Article
Indigenous management helped shape northern California forests for over 1000 years

Indigenous management helped shape northern California forests for over 1000 years

This article is part of the Spring 2022 issue of the Earth Science Matters Newsletter.

Read Article
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