Data

Gridded SAM and ENSO coefficients derived from satellite altimeter data over the Antarctic Ice Sheet, 2002-2020

Australian Ocean Data Network
King, Matt ; Christoffersen, Poul
Viewed: [[ro.stat.viewed]] Cited: [[ro.stat.cited]] Accessed: [[ro.stat.accessed]]
ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rfr_id=info%3Asid%2FANDS&rft_id=http://catalogue-aodn.prod.aodn.org.au/geonetwork/srv/eng/search?uuid=cf3f6302-de8b-449b-80fb-cc757dcc454f&rft.title=Gridded SAM and ENSO coefficients derived from satellite altimeter data over the Antarctic Ice Sheet, 2002-2020&rft.identifier=http://catalogue-aodn.prod.aodn.org.au/geonetwork/srv/eng/search?uuid=cf3f6302-de8b-449b-80fb-cc757dcc454f&rft.description=The data result from an analysis of gridded satellite altimetry time series of ice surface elevation for the Antarctic Ice Sheet. Multiple linear regression is performed, including parameters associated with the cumulative sum of each of the Southern Annular Mode (SAM) and El Nino/Southern Oscillation (ENSO). The gridded data include the original data and the derived parameters and statistical values. Four grids are provided. Two grids are from separate regressions performed on data after applying one of two different spatial smoothing filters (10 km and 200 km Gaussian functions). Two further grids are from regressions after subtracting one of two firn densification models from the 10 km-smoothed altimetry data.Maintenance and Update Frequency: notPlannedStatement: We make use of an existing gridded altimeter product (Nilsson et al. 2023) at 1920 m horizontal resolution and covering the period from April 1985 to December 2020 (Nilsson et al. 2022). We spatially down-sample this to 5 km horizontal resolution. To facilitate comparison with space gravimetry data we only make use of data from 2002 to the end of the record. The dataset contains monthly ice-sheet elevation-change data derived from a range of radar and laser altimeter missions; over the study period these are ERS-2, Envisat and CryoSat-2 and ICESat and ICESat-2. To reduce spatial noise we apply a Gaussian smoother with widths specified in later sections. For these, width is defined at the half height of the Gaussian function, consistent with the definition commonly used in GRACE data smoothing. We also use the existing COST-G RL01 Level-3 50 km gridded ice-mass change per surface area GRACE and GRACE-FO V0002 dataset obtained from http://gravis.gfz-potsdam.de/antarctica. We make use of data from March 2002 to December 2020, with the end point chosen to match the end of the altimetry dataset. The data are spaced approximately monthly and with a data gap of ~12 months between GRACE and GRACE-FO from mid-2017 to mid-2018. We compare the altimeter and GRACE data primarily with SAM and ENSO indices, with additional comparison to Amundsen Sea Low (ASL) indices in the Amundsen Sea region. For the ASL indices, we make use of both the absolute center pressure (ASLP) and longitude (ASLλ) within the ASL Index version 3.20210820-era5 based on monthly ERA5 reanalysis data. For SAM, we make use of the Marshall station index. For ENSO, we make use of the Nino3.4 index based on the HadISST1 dataset (Rayner 2003) and use a 6-month lag. We normalised each index with the mean and standard deviation computed over 1971-1999 inclusive, then cumulatively summed them, limited them to the data period, and then renormalized to produce SAMΣ, ENSOΣ, ASLPΣ, and ASLλΣ. We use ordinary linear least squares to solve for coefficients related to a constant, trend, harmonic terms for 1 and 2 cycles per year, and one for each of the SAM and ENSO terms.&rft.creator=King, Matt &rft.creator=Christoffersen, Poul &rft.date=2024&rft.coverage=westlimit=0; southlimit=-90.00; eastlimit=0; northlimit=-60.00&rft.coverage=westlimit=0; southlimit=-90.00; eastlimit=0; northlimit=-60.00&rft_rights=This dataset is hosted by the University of Tasmania, on behalf of the Australian Centre for Excellence in Antarctic Science. This research was supported by the Australian Research Council Special Research Initiative, Australian Centre for Excellence in Antarctic Science (Project Number SR200100008).&rft_rights=&rft_rights= https://creativecommons.org/licenses/by/4.0/&rft_rights=https://licensebuttons.net/l/by/4.0/88x31.png&rft_rights=WWW:LINK-1.0-http--related&rft_rights=License Graphic&rft_rights=Creative Commons Attribution 4.0 International License&rft_rights=CC-BY&rft_rights=4.0&rft_rights=http://creativecommons.org/international/&rft_rights=WWW:LINK-1.0-http--related&rft_rights=WWW:LINK-1.0-http--related&rft_rights=License Text&rft_rights=Cite data as: King, M & Christoffersen, P (2024). Gridded SAM and ENSO coefficients derived from satellite altimeter data over the Antarctic Ice Sheet, 2002-2020 [Data set]. Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS). https://doi.org/10.25959/MKAIS-D424&rft_rights=Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0&rft_subject=climatologyMeteorologyAtmosphere&rft_subject=satellite altimetry&rft_subject=GRACE gravimetry&rft_subject=Southern Annular Mode (SAM)&rft_subject=El Nino Southern Oscillation (ENSO)&rft_subject=GLACIER MASS BALANCE/ICE SHEET MASS BALANCE&rft_subject=EARTH SCIENCE&rft_subject=CRYOSPHERE&rft_subject=GLACIERS/ICE SHEETS&rft_subject=CLIMATE INDICATORS&rft_subject=GLACIER ELEVATION/ICE SHEET ELEVATION&rft_subject=CRYOSPHERIC INDICATORS&rft_subject=GLACIAL MEASUREMENTS&rft_subject=ice elevation&rft_subject=altimeter&rft_subject=Continents | Continents | Antarctica&rft_subject=GEOMATIC ENGINEERING&rft_subject=ENGINEERING&rft_subject=Geomorphology and Regolith and Landscape Evolution&rft_subject=EARTH SCIENCES&rft_subject=PHYSICAL GEOGRAPHY AND ENVIRONMENTAL GEOSCIENCE&rft_subject=Glaciology&rft.type=dataset&rft.language=English Access the data

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This dataset is hosted by the University of Tasmania, on behalf of the Australian Centre for Excellence in Antarctic Science. This research was supported by the Australian Research Council Special Research Initiative, Australian Centre for Excellence in Antarctic Science (Project Number SR200100008).

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License Text

Cite data as: King, M & Christoffersen, P (2024). Gridded SAM and ENSO coefficients derived from satellite altimeter data over the Antarctic Ice Sheet, 2002-2020 [Data set]. Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS). https://doi.org/10.25959/MKAIS-D424

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Brief description

The data result from an analysis of gridded satellite altimetry time series of ice surface elevation for the Antarctic Ice Sheet. Multiple linear regression is performed, including parameters associated with the cumulative sum of each of the Southern Annular Mode (SAM) and El Nino/Southern Oscillation (ENSO). The gridded data include the original data and the derived parameters and statistical values. Four grids are provided. Two grids are from separate regressions performed on data after applying one of two different spatial smoothing filters (10 km and 200 km Gaussian functions). Two further grids are from regressions after subtracting one of two firn densification models from the 10 km-smoothed altimetry data.

Lineage

Maintenance and Update Frequency: notPlanned
Statement: We make use of an existing gridded altimeter product (Nilsson et al. 2023) at 1920 m horizontal resolution and covering the period from April 1985 to December 2020 (Nilsson et al. 2022). We spatially down-sample this to 5 km horizontal resolution. To facilitate comparison with space gravimetry data we only make use of data from 2002 to the end of the record. The dataset contains monthly ice-sheet elevation-change data derived from a range of radar and laser altimeter missions; over the study period these are ERS-2, Envisat and CryoSat-2 and ICESat and ICESat-2. To reduce spatial noise we apply a Gaussian smoother with widths specified in later sections. For these, width is defined at the half height of the Gaussian function, consistent with the definition commonly used in GRACE data smoothing.

We also use the existing COST-G RL01 Level-3 50 km gridded ice-mass change per surface area GRACE and GRACE-FO V0002 dataset obtained from http://gravis.gfz-potsdam.de/antarctica. We make use of data from March 2002 to December 2020, with the end point chosen to match the end of the altimetry dataset. The data are spaced approximately monthly and with a data gap of ~12 months between GRACE and GRACE-FO from mid-2017 to mid-2018.

We compare the altimeter and GRACE data primarily with SAM and ENSO indices, with additional comparison to Amundsen Sea Low (ASL) indices in the Amundsen Sea region. For the ASL indices, we make use of both the absolute center pressure (ASLP) and longitude (ASLλ) within the ASL Index version 3.20210820-era5 based on monthly ERA5 reanalysis data. For SAM, we make use of the Marshall station index. For ENSO, we make use of the Nino3.4 index based on the HadISST1 dataset (Rayner 2003) and use a 6-month lag. We normalised each index with the mean and standard deviation computed over 1971-1999 inclusive, then cumulatively summed them, limited them to the data period, and then renormalized to produce SAMΣ, ENSOΣ, ASLPΣ, and ASLλΣ.

We use ordinary linear least squares to solve for coefficients related to a constant, trend, harmonic terms for 1 and 2 cycles per year, and one for each of the SAM and ENSO terms.

Notes

Credit
Australian Centre for Excellence in Antarctic Science
Credit
This work was supported by the ARC Australian Centre for Excellence in Antarctic Science (Project ID SR200100008)

Issued: 24 04 2024

Data time period: 2002-01-01 to 2020-12-31

This dataset is part of a larger collection

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text: westlimit=0; southlimit=-90.00; eastlimit=0; northlimit=-60.00

Other Information
(DATA ACCESS - satellite altimetry data (3.54 GB zipped) [direct download])

uri : https://data.imas.utas.edu.au/attachments/cf3f6302-de8b-449b-80fb-cc757dcc454f

Identifiers
  • global : cf3f6302-de8b-449b-80fb-cc757dcc454f