Seasonal Antarctic pressure variability during the twentieth century from spatially complete reconstructions and CAM5 simulations

Fogt, Ryan L.; Schneider, David P.; Goergens, Chad A.; Jones, Julie Miller; Clark, L.; Garberoglio, Michael

doi:10.1007/s00382-019-04674-8

Cited by 18 publications

(59 citation statements)

References 45 publications

(9 reference statements)

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“…As an extension of SAM index reconstructions, the relationship between pressure in the SH mid-latitudes with Antarctica was further employed to reconstruct seasonal mean pressure observations at 18 Antarctic stations back to 1905 [28,29]. Both SAM index reconstructions and the pressure reconstructions at select stations indicate that ozone depletion is an important mechanism for recent changes in the Antarctic atmospheric circulation in austral summer [29][30][31][32][33], consistent with other work [34,35].…”

Section: Introductionsupporting

confidence: 70%

“…For this study, the National Center for Atmospheric Research (NCAR) Community Atmospheric Model version 5 (CAM5) is configured at a 0.9 • latitude × 1.25 • longitude horizontal resolution, with a finite volume dynamical core and 26 vertical levels [32]. CAM5 is a non-coupled atmosphere-only climate model, and three experiments representing the main known forcing mechanisms on SH climate variability and change during the entire 20th century are analyzed here to help isolate the sensitivity of various external forcings as in earlier work [32,33]. In addition, each experiment is comprised of 10 ensemble members, each initialized with a random perturbation in air temperature.…”

Section: Cam5mentioning

confidence: 99%

“…Apart from reconstructions, climate model experiments are important tools for understanding historical Antarctic climate and (for example) have been used to evaluate the effect of the SAM on Antarctic temperature [38], West Antarctic climate variability [39] and Antarctic pressure [32,33]. However, the reliability of climate models in accurately representing Antarctic climate is again challenging to fully determine, as comparison with observations can only be made since 1957 and even shorter for Antarctic sea ice [40].…”

Section: Introductionmentioning

confidence: 99%

“…Second, although imperfect, it is a continuous dataset, allowing us to fully examine changes in the strength of the pressure relationship between the mid and high latitudes of the SH and better quantify the overall reconstruction skill purely within the model (since direct data withheld outside a calibration window in the model can be used for comparison). Third, using multiple experiments as in previous work [32,33] allows to determine if any particular prescribed forcing mechanisms significantly influence the mid-to-high latitude SH pressure relationships. It has been suggested that stratospheric ozone depletion has directly influenced the strengthening of the Amundsen Sea Low [45], which is a climatological low pressure center known for its extensive influence on West Antarctic climate variability [46].…”

Section: Introductionmentioning

confidence: 99%

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Southern Hemisphere Pressure Relationships during the 20th Century—Implications for Climate Reconstructions and Model Evaluation

Clark

Fogt

2019

Geosciences

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The relationship between Southern Hemisphere middle and high-latitude regions has made it possible to generate observationally-based Antarctic pressure reconstructions throughout the 20th century, even though routinely collected observations for this continent only began around 1957. While nearly all reconstructions inherently assume stability in these relationships through time and in the absence of direct observations, this stationarity constraint can be fully tested in a model setting. Seasonal pressure reconstructions based on the principal component regression (PCR) method spanning 1905–2013 are done entirely within the framework of the Community Atmospheric version 5 (CAM5) model in this study in order to evaluate this assumption, test the robustness of the PCR procedure for Antarctic pressure reconstructions and to evaluate the CAM5 model. Notably, the CAM5 reconstructions outperformed the observationally-based reconstruction in every season except the austral summer. Other tests indicate that relationships between Antarctic pressure and pressure across the Southern Hemisphere remain stable throughout the 20th century in CAM5. In contrast, 20th century reanalyses all display marked changes in mid-to-high latitude pressure relationships in the early 20th century. Overall, comparisons indicate both the CAM5 model and the pressure reconstructions evaluated here are reliable estimates of Antarctic pressure throughout the 20th century, with the largest differences between the two resulting from differences in the underlying reconstruction predictor networks and not from changes in the model experiments.

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Section: Introductionsupporting

confidence: 70%

Section: Cam5mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Southern Hemisphere Pressure Relationships during the 20th Century—Implications for Climate Reconstructions and Model Evaluation

Clark

Fogt

2019

Geosciences

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“…Reconstruction skill was found to be better in austral summer than in winter. These reconstructions were extended to produce a gridded surface pressure reconstruction poleward of 60 • S in Austral summer, and forcing mechanisms of the reconstructed pressure changes were explored through comparison with simulations with the Community Atmospheric Model, version 5 (CAM5) [131]. These reconstructions offer the possibility of both further use for model evaluation, as well as for comparison with, and calibration of, proxy records.…”

Section: Current Challengesmentioning

confidence: 99%

Back to the Future: Using Long-Term Observational and Paleo-Proxy Reconstructions to Improve Model Projections of Antarctic Climate

et al. 2019

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Quantitative estimates of future Antarctic climate change are derived from numerical global climate models. Evaluation of the reliability of climate model projections involves many lines of evidence on past performance combined with knowledge of the processes that need to be represented. Routine model evaluation is mainly based on the modern observational period, which started with the establishment of a network of Antarctic weather stations in 1957/58. This period is too short to evaluate many fundamental aspects of the Antarctic and Southern Ocean climate system, such as decadal-to-century time-scale climate variability and trends. To help address this gap, we present a new evaluation of potential ways in which long-term observational and paleo-proxy reconstructions may be used, with a particular focus on improving projections. A wide range of data sources and time periods is included, ranging from ship observations of the early 20th century to ice core records spanning hundreds to hundreds of thousands of years to sediment records dating back 34 million years. We conclude that paleo-proxy records and long-term observational datasets are an underused resource in terms of strategies for improving Antarctic climate projections for the 21st century and beyond. We identify priorities and suggest next steps to addressing this.

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An assessment of early 20th century Antarctic pressure reconstructions using historical observations

Fogt

Belak

Jones

et al. 2020

Intl Journal of Climatology

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While gridded seasonal pressure reconstructions poleward of 60 S extending back to 1905 have been recently completed, their skill has not been assessed prior to 1958. To provide a more thorough evaluation of the skill and performance in the early 20th century, these reconstructions are compared to other gridded datasets, historical data from early Antarctic expeditions, ship records, and temporary bases. Overall, the comparison confirms that the reconstruction uncertainty of 2-4 hPa (evaluated after 1979) over the Southern Ocean is a valid estimate of the reconstruction error in the early 20th century. Over the interior and near the coast of Antarctica, direct comparisons with historical data are challenged by elevation-based reductions to sea level pressure. In a few cases, a simple linear adjustment of the reconstruction to sea level matches the historical data well, but in other cases, the differences remain greater than 10 hPa. Despite these large errors, comparisons with continuous multi-season observations demonstrate that aspects of the interannual variability are often still captured, suggesting that the reconstructions have skill representing variations on this timescale, even if it is difficult to determine how well they capture the mean pressure at these higher elevations. Additional comparisons with various 20th-century reanalysis products demonstrate the value of assimilating the historical observations in these datasets, which acts to substantially reduce the reanalysis ensemble spread, and bring the reanalysis ensemble mean within the reconstruction and observational uncertainty.

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Seasonal Antarctic pressure variability during the twentieth century from spatially complete reconstructions and CAM5 simulations

Cited by 18 publications

References 45 publications

Southern Hemisphere Pressure Relationships during the 20th Century—Implications for Climate Reconstructions and Model Evaluation

Southern Hemisphere Pressure Relationships during the 20th Century—Implications for Climate Reconstructions and Model Evaluation

Back to the Future: Using Long-Term Observational and Paleo-Proxy Reconstructions to Improve Model Projections of Antarctic Climate

An assessment of early 20th century Antarctic pressure reconstructions using historical observations

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