Joseph R. McConnell

Desert Research Institute

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Michael Sigl

Oeschger Centre for Climate Change Research

Nathan Chellman

Desert Research Institute

Roger C. Bales

University of California, Merced

Edward J. Brook

Oregon State University

O. J. Maselli

Nevada System of Higher Education

Rachael H. Rhodes

University of Cambridge

Monica M. Arienzo

Desert Research Institute

Eric J. Steig

University of Washington

Ross Edwards

University of Wisconsin–Madison

J. P. Steffensen

University of Copenhagen

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Centre National de la Recherche Scientifique

118

University of Copenhagen

University of Colorado Boulder

University of Washington

University of Bern

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Université Grenoble Alpes

Oeschger Centre for Climate Change Research

Desert Research Institute

Goddard Space Flight Center

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Comment on essd-2022-368

Elizabeth R. Thomas Diana Vladimirova Dieter Tetzner B. Daniel Emanuelsson Nathan Chellman

Abstract. Changes in sea ice conditions and atmospheric circulation over the Southern Ocean play an important role in modulating Antarctic climate. However, observations of both sea ice and wind conditions are limited in Antarctica and the Southern Ocean, both temporally and spatially. Ice core chemistry data can be used to reconstruct changes over annual, decadal, and millennial timescales. To facilitate sea ice and wind reconstructions, the CLIVASH2k working group has compiled a database of two species, sodium [Na⁺] and sulphate [SO₄^2-], commonly measured ionic species. The database contains records from 105 Antarctic ice cores, containing records with a maximum age duration of 2000 years. An initial filter has been applied, based on evaluation against climate observations, to identify sites suitable for reconstructing past sea ice conditions, wind strength, or atmospheric circulation.

Ice core

10.5194/essd-2022-368-rc2

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Influence of North Atlantic Oscillation on anthropogenic transport recorded in northwest Greenland ice cores

Journal of Geophysical Research Atmospheres (2006)

J. F. Burkhart Roger C. Bales Joseph R. McConnell M. A. Hutterli

Nitrate records from six Greenland ice cores covering the period 1789 to 1995 show a significant correlation in concentration for averaging periods greater than 10 years, as well as an approximately 60% increase in average concentration during the last 75 years. Annual nitrate fluxes contain low‐frequency trends driven primarily by changes in concentration, while higher‐frequency variability is driven by changes in snow accumulation. Increases in concentration yield nearly 30% higher nitrate flux (2.5 to 3.2 μ g m −2 yr −1 ) and an 11% increase in variability during the 1895 to 1994 period versus the prior 100 years. Nitrate trends in the cores during the last 100 years are also correlated with global nitrate emissions, with a highly significant average r value of 0.93 for the six cores. During the period of anthropogenic influence, nitrate is positively correlated with the North Atlantic Oscillation, while prior to that the correlation is negative, and less significant, suggesting a link between transport of anthropogenic emissions and the North Atlantic Oscillation. Significant preanthropogenic periodicities identified through singular spectrum analysis show decadal variability in the nitrate record leading to shifts as great as 30% from the mean state but none as great as the anthropogenic‐driven deviation.

Ice core

Groenlandia

10.1029/2005jd006771

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Citations (28)

Ice Core and Marine Sediment Records of Quaternary Environmental Change

Joseph R. McConnell Sandra O. Brugger Nathan Chellman

Ice core and marine sediment records provide detailed evidence of quaternary environmental change and have been used widely to help place observed recent changes in a long-term perspective, as well as to evaluate linkages between the environment and human societies. Physical parameters in ice cores are routinely used in paleoenvironmental studies. Ice cores usually are drilled vertically in the accumulation zones of ice sheets and glaciers since the objective is to obtain well-dated, continuous paleoenvironmental records. Ice cores typically are analyzed for a broad range of isotopic ratios, chemical and elemental concentrations, and other properties, with the range of the measurements and sample resolutions determined by the objectives, scope, and budget of the research project. This chapter provides a brief introduction to different measurement methods typically used to analyze ice core samples for water isotope ratios, aerosols-related elements, chemical species, and gases.

Ice core

Environmental change

10.1002/9781119592112.ch9

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Reply to: Black carbon attribution

Nature (2022)

Joseph R. McConnell Nathan Chellman A. Stohl

10.1038/s41586-022-05519-x

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Erratum: errata: Changes in Greenland ice sheet elevation attributed primarily to snow accumulation variability

Nature (2001)

Joseph R. McConnell Robert J. Arthern Ellen Mosley‐Thompson Curt H. Davis Roger C. Bales

Greenland ice sheet

Elevation (ballistics)

Satellite Altimetry

10.1038/35065662

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Citations (1)

Instruments and Methods Dating annual layers of a shallow Antarctic ice core with an optical scanner

Kenneth C. McGwire Joseph R. McConnell Richard B. Alley J. Ryan Banta Geoffrey M. Hargreaves

This study tests novel methods for automatically identifying annual layers in a shallow Antarctic ice core (WDC05Q) using images that were collected with an optical scanner at the US National Ice Core Laboratory. A new method of optimized variance maximization (OVM) modeled the density-related changes in annual layer thickness directly from image variance. This was done by using multi-objective complex (MOCOM) parameter optimization to drive a low-pass filtering scheme. The OVM-derived changes in annual layer thickness corresponded well with the results of an independent glaciochemical interpretation of the core. Individual annual cycles in image brightness were then identified by using OVM results to apply a depth-varying low-pass filter and fitting a second-order polynomial to a locally detrended neighborhood. The resulting map of annual cycles agreed to within 1% of the overall annual count of the glaciochemical interpretation. Agreement on the presence of specific annual layer features was 96%. It was also shown that the MOCOM parameter optimization could calibrate the image-based results to match directly the date of a specific volcanic marker.

Ice core

Source

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Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise

Science (2005)

Curt H. Davis Frank Yonghong Li Joseph R. McConnell M. M. Frey Edward Hanna

Satellite radar altimetry measurements indicate that the East Antarctic ice-sheet interior north of 81.6 degrees S increased in mass by 45 +/- 7 billion metric tons per year from 1992 to 2003. Comparisons with contemporaneous meteorological model snowfall estimates suggest that the gain in mass was associated with increased precipitation. A gain of this magnitude is enough to slow sea-level rise by 0.12 +/- 0.02 millimeters per year.

Antarctic ice sheet

Future sea level

10.1126/science.1110662

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Citations (280)

Formaldehyde and hydrogen peroxide in air, snow and interstitial air at South Pole

Atmospheric Environment (2004)

M. A. Hutterli Joseph R. McConnell Gao Chen Roger C. Bales Douglas D. Davis

Snowpack

Firn

Deposition

Mixing ratio

10.1016/j.atmosenv.2004.06.003

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Citations (100)

Incandescence‐based single‐particle method for black carbon quantification in lake sediment cores

Limnology and Oceanography Methods (2018)

Nathan Chellman Joseph R. McConnell Alan C. Heyvaert Boris Vannière Monica M. Arienzo

Abstract Refractory black carbon (rBC) is an important contributor to radiative forcing, so quantifying rBC emissions and transport is critical for accurate climate modeling. Formed during incomplete combustion of fossil fuels or biofuels, rBC is emitted to the atmosphere from large wildfires and industrial sources where it can be transported and deposited globally. Ice cores have been used to reconstruct historical changes in biomass burning and industrial emissions but they are available only from glaciers and ice sheets, with reliable records longer than a few centuries generally limited to polar regions. Lake sediment cores provide a possible alternative to develop longer term, widely distributed records from mid‐ and low‐latitude regions, albeit with lower temporal resolution and less directly linked to atmospheric concentrations than ice‐core rBC records. Here, we present a new incandescence‐based method for measuring rBC in lake sediment cores using the Single‐Particle Soot Photometer. Compared to existing filter‐based techniques, this highly sensitive method requires a much smaller sample size, resulting in reproducible, relatively high‐temporal‐resolution records of past rBC deposition.

Ice core

Incandescence

Mineral dust

Deposition

10.1002/lom3.10276

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Citations (6)

Sensitivity of hydrogen peroxide (H₂O₂) and formaldehyde (HCHO) preservation in snow to changing environmental conditions: Implications for ice core records

Journal of Geophysical Research Atmospheres (2003)

M. A. Hutterli Joseph R. McConnell Roger C. Bales Richard W. Stewart

Sensitivity studies with physically based numerical air–snow–firn transfer models for formaldehyde (HCHO) and hydrogen peroxide (H 2 O 2 ) show that even though nonlinear processes determine the preservation of HCHO and H 2 O 2 in snow and firn, changes in atmospheric mixing ratios are linearly recorded in ice cores under otherwise constant environmental conditions. However, temperature, snowpack ventilation, and rate and timing of snow accumulation also affect the ice core records of reversibly deposited species and must be considered when inferring past atmospheric mixing ratios. The results of the sensitivity studies allow quantitative separation of these factors in ice core records. Past temperatures and accumulation rates are generally determined in ice cores and the preservation of HCHO and H 2 O 2 is not highly sensitive to snowpack ventilation, leaving changes in seasonality of snow accumulation as the main source of uncertainty in a reconstruction of past atmospheric mixing ratios.

Snowpack

Firn

Ice core

Mixing ratio

10.1029/2002jd002528

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Citations (71)