ORCID Profile
0000-0002-7422-1469
Current Organisations
Alluvium Consulting Australia Pty Ltd
,
University of Tasmania
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Publisher: Copernicus GmbH
Date: 20-06-2023
DOI: 10.5194/ESSD-15-2517-2023
Abstract: 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, prior to the satellite era (1970 onwards). 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 (CLimate Variability in Antarctica and the Southern Hemisphere over the past 2000 years) working group has compiled a database of two species, sodium [Na+] and sulfate [SO42-], commonly measured ionic species. The database (0.5285/9E0ED16E-F2AB-4372-8DF3-FDE7E388C9A7 Thomas et al., 2022) comprises 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 sea ice concentration, geopotential height (500 hPa), and surface wind fields to identify sites suitable for reconstructing past sea ice conditions, wind strength, or atmospheric circulation.
Publisher: American Meteorological Society
Date: 02-2020
Abstract: Weather systems in the southern Indian Ocean (SIO) drive synoptic-scale precipitation variability in East Antarctica and southern Australia. Improved understanding of these dynamical linkages is beneficial to diagnose long-term climate changes from climate proxy records as well as informing regional weather and climate forecasts. Self-organizing maps (SOMs) are used to group daily 500-hPa geopotential height (z500 ERA-Interim) anomalies into nine regional synoptic types based on their dominant patterns over the SIO (30°–75°S, 40°–180°E) from January 1979 to October 2018. The pattern anomalies represented include four meridional, three mixed meridional–zonal, one zonal, and one transitional node. The frequency of the meridional nodes shows limited association with the phase of the southern annular mode (SAM), especially during September–November. The zonal and mixed patterns were nevertheless strongly and significantly correlated with SAM, although the regional synoptic representation of SAM+ conditions was not zonally symmetric and was represented by three separate nodes. We recommend consideration of how different synoptic conditions vary the atmospheric representation of SAM+ in any given season in the SIO. These different types of SAM+ mean a hemispheric index fails to capture the regional variability in surface weather conditions that is primarily driven by the synoptic variability rather than the absolute polarity of the SAM.
Publisher: Copernicus GmbH
Date: 12-12-2022
Abstract: 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 [SO42-], 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.
Publisher: Copernicus GmbH
Date: 12-12-2022
Publisher: Springer Science and Business Media LLC
Date: 04-08-2022
DOI: 10.1038/S43247-022-00502-W
Abstract: Previous research has shown that aerosol sea salt concentrations (Southern Ocean wind proxy) preserved in the Law Dome ice core (East Antarctica) correlate significantly with subtropical eastern Australian rainfall. However, physical mechanisms underpinning this connection have not been established. Here we use synoptic typing to show that an atmospheric bridge links East Antarctica to subtropical eastern Australia. Increased ice core sea salt concentrations and wetter conditions in eastern Australia are associated with a regional, asymmetric contraction of the mid-latitude westerlies. Decreased ice core sea salt concentrations and drier eastern Australia conditions are associated with an equatorward shift in the mid-latitude westerlies, suggesting greater broad-scale control of eastern Australia climate by southern hemisphere variability than previously assumed. This relationship explains double the rainfall variance compared to El Niño-Southern Oscillation during late spring-summer, highlighting the importance of the Law Dome ice core record as a 2000-year proxy of eastern Australia rainfall variability.
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-3756
Abstract: & & Weather systems in the southern Indian Ocean drive synoptic-scale precipitation, temperature and wind variability in East Antarctica, sub-Antarctic islands and southern Australia. & Over seasonal to decadal timescales, the mean condition associated with combinations of these synoptic weather patterns (e.g., extratropical cyclones, fronts and regions of high pressure) is often referred to as variability in the westerly wind belt or the Southern Annular Mode (SAM). The westerly wind belt is generally considered to be zonally symmetric around Antarctica however, on a daily timescale this is not the case. To capture the daily variability of regional weather systems, we used synoptic typing (Self-Organising Maps) to group weather patterns based on similar features, which are often lost when using monthly or seasonal mean fields. We identified nine key regional weather types based on anomaly pattern and strength. These include four meridional nodes, three mixed nodes, one zonal node and one transitional node. The meridional nodes are favourable for transporting warm, moist air masses to the subantarctic and Antarctic region, and are associated with increased precipitation and temperature where the systems interact with the Antarctic coastline. & These nodes have limited association with the SAM, especially during austral spring.& In contrast, the zonal and mixed nodes were strongly correlated with the SAM however, the regional synoptic representation of SAM positive conditions is not zonally symmetric and is represented by three separate nodes.& These different types of SAM positive conditions mean that the commonly used hemispheric Marshall index often fails to capture the regional variability in surface weather conditions in the southern Indian Ocean. Our results show the importance of considering different synoptic set ups of SAM conditions, particularly SAM positive, and identify conditions that are potentially missed by SAM variability (e.g., extreme precipitation events). Our results are particularly important to consider when interpreting SAM or westerly wind belt reconstructions in the study region (from ice cores, tree rings, or lake sediments). & Here we present a case study using the synoptic typing results to enhance our understanding of the Law Dome (East Antarctica) ice core record, focussing on links to large scale modes of climate variability and Australian hydroclimate.& These results enhance the usefulness of ice core proxies in coastal East Antarctica and assist with determining where and how it is appropriate to use coastal East Antarctic ice core records for reconstructions of large scale modes of climate variability (e.g. SAM and ENSO) and remote hydroclimate conditions.& &
Publisher: Authorea, Inc.
Date: 11-09-2023
No related grants have been discovered for Danielle Udy.