| NSF Org: |
OPP Office of Polar Programs (OPP) |
| Recipient: |
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| Initial Amendment Date: | August 2, 2018 |
| Latest Amendment Date: | August 2, 2018 |
| Award Number: | 1745089 |
| Award Instrument: | Standard Grant |
| Program Manager: |
David Porter
dporter@nsf.gov (703)292-2930 OPP Office of Polar Programs (OPP) GEO Directorate For Geosciences |
| Start Date: | September 1, 2018 |
| End Date: | April 30, 2023 (Estimated) |
| Total Intended Award Amount: | $314,700.00 |
| Total Awarded Amount to Date: | $314,700.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
10889 WILSHIRE BLVD STE 700 LOS ANGELES CA US 90024-4200 (310)794-0102 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1255 Bunche Hall Los Angeles CA US 90095-1524 |
| Primary Place of Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | ANT Ocean & Atmos Sciences |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
In contrast to the Arctic, sea ice cover in most Antarctic regions has increased since 1979. The area-integrated total sea ice extent grew to record maximum values in four of the last six years, yet the 2015-16 summer was marked by record low ice cover. While impressive, it is difficult to assess the significance of these very recent records in the context of longer term variability, since the continuous satellite record only dates back to 1978. The limited length of the continuous sea ice record, is a significant confounding factor in ascertaining whether the observed current changes are due to natural variability alone, or represent a forced anthropogenic response. As a result, the scientific understanding of the Antarctic sea ice trends remains poor, as does confidence in projections of future Antarctic sea ice trends.
To address this challenge, this project seeks to reconstruct sea ice extent and sea ice concentration, using the relationships between satellite-observed sea ice, sea level pressure, tropical sea surface temperature, ENSO indices, some proxy data (ice cores, etc.), and in situ Southern Ocean temperature data. The aim of the study is to collect and combine these ancillary records as accurately as possible while retaining the variability associated with the intrinsic uncertainty in the available field data.
A range of statistical methods for modelling the relationship between satellite era sea-ice data using flexible regression, Bayesian and multivariate dynamic spatial temporal (MDST) methods will be used.
The study will entrain cross-disciplinary training of undergraduate and a graduate student at UCLA and Ohio University.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Until 2016, satellite-observed Antarctic sea ice extent had been experiencing a small, positive trend. That trend does not now exist because of record summer minima in 2017, 2022 and 2023. The timeseries of satellite-observed data is too short to allow statistically robust assessment of these variations. We cannot use them to tell if this variability is normal, if it has occurred in the past or if it represents a change in the sea ice system. To do this we need to have a sense of how Antarctic sea ice has varied in the past. This project used the principles of Bayesian statistics in a novel manner, and the information about the physical relationship between Antarctic sea ice and climate variability gleaned from a network of 30 Southern Hemisphere weather stations to estimate the sea ice extent for the pre-satellite 20th Century. Specifically, we have produced and validated ensemble reconstructions of monthly sea ice extent around Antarctica, extending from 1905 to the present.
We have produced ensembles for each of the five sea ice sectors around Antarctica as well as the total sea ice extent which is the sum of all five sectors. Figure 1 shows the reconstructions for the total as well as the five sea ice sectors.
These reconstructions represent a significant advance on our knowledge of Antarctic sea ice variability in the pre-satellite 20th Century. We can now place the contemporary variation of Antarctic sea ice into context. For example, we can say with statistical certainty that it is unlikely that the recent record minima occurred in the 20th Century. We can also use these reconstructions to query whether or not the recent Antarctic sea ice variability represents a change in the sea ice system and to project the future state of the system. The latter ability has global, societal significance because Antarctic sea ice plays an important role in mediating global climate as well as global sea level changes.
We have also completed development of software that will allow others to reproduce the Bayesian reconstruction and validation procedures. And the data will be archived and publicly available for use at the National Snow and Ice Data Center.
Last Modified: 08/28/2023
Modified by: Mark S Handcock
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Ensemble reconstruction of 20th century Antarctic sea ice. Individual reconstructions are drawn in light gray, the average reconstruction in red, and observed sea ice in blue.CopyrightedCopyrightedMark S HandcockEnsemble reconstruction of 20th century Antarctic sea ice
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