[Parameters: Topic='ATMOSPHERE', Term='AEROSOLS', Variable_Level_1='DUST/ASH/SMOKE']
An assessment of variability in the influx of cosmic dust during the Holocene and the potential effect on iron concentrations in the Southern Ocean.Entry ID: AAS_3132
Abstract: Metadata record for data from AAS (ASAC) project 3132.
This research will determine variability in the influx and mineralogy of cosmic dust to the Southern Ocean during the Holocene from peat bog cores. Cosmic dust contains significant quantities of soluble iron, a micronutrient required for photosynthesis. Therefore, variations in the deposition of cosmic dust could significantly affect ... primary production in the Southern Ocean. This may also play an important role in global climate due to its influence on carbon dioxide draw-down from, and emission of volatile sulphur compounds to, the atmosphere.
The download file contain a csv spreadsheet of carbon dating from geochemical peat cores collected from Green Gorge on Macquarie Island.
This project will sample peat bogs on Macquarie Island to:
1. Quantify and develop a high-temporal resolution record of the variability in cosmic dust deposition during the Holocene;
2. Determine the mineralogy and quantify the solubility of iron contained in the cosmic dust;
Iron is a micronutrient required for photosynthetic reactions within chloroplasts. Martin  proposed that many oceanic phytoplankton, especially those in the high nutrient - low chlorophyll (HNLC) regions of the world's oceans (such as the Southern Ocean) were limited by the availability of iron. Martin et al.  demonstrated that nanomolar increases in dissolved iron stimulated phytoplankton blooms in the North and Equatorial Pacific and Southern Oceans. Several large-scale field experiments (see de Baar et al  for a summary) demonstrated that the addition of iron stimulated phytoplankton productivity significantly. Eleven further experiments have confirmed these results in many other regions [Boyd, et al., 2007] and models of the cellular processes by which iron fertilisation stimulates phytoplankton blooms are now available [Fasham, et al., 2006]. The response of phytoplankton to iron fertilisation has attracted much research effort because phytoplankton blooms increase the draw-down of carbon from the atmosphere and ultimately export a fraction to the deep ocean where it is stored as particulate organic carbon [Watson, et al., 2000] and hence may play an important role in climate.
Cosmic and terrestrial dust can both contain significant quantities of soluble, bio-available iron [Fung, et al., 2000; Plane, 2003]. The potential for iron contained in aeolian terrestrial dust to affect climate was recently assessed by Kohfeld et al. , who concluded that dust-induced iron-fertilisation of ocean ecosystems might account for 30 - 50 ppm of atmospheric CO2 draw-down during the last glacial period. Satellite data provide support for these hypotheses at the regional scales at which terrestrial dust deposition events occur [Cropp, et al., 2003; Gabric, et al., 2002]. The influx of cosmic dust to the oceans could be significantly different to terrestrial dust inputs as it is likely to be uniformly distributed around the globe [Johnson, 2001], vary on longer time scales (although this is not well understood [Winckler and Fischer, 2006]), and is expected to be of finer particle-size and contrasting mineralogy [Plane, 2003].
Ice cores provide excellent long-term records of terrestrial and cosmic dust deposition, however, cores from ombrotrophic peat bogs, that receive their inputs exclusively from the atmosphere, can provide high temporal resolution records of cosmic and terrestrial dust during the Holocene [Cortizas and Gayoso, 2002]. Data from ice cores in Greenland and ocean sediment cores in the tropical Pacific have revealed variations in cosmic dust influx between glacial and inter-glacial periods, with increases in cosmic dust influx associated with cooler temperatures [Dalai, et al., 2006; Gabrielli, et al., 2004; Karner, et al., 2003]. Johnson  calculated that the current background cosmic dust deposition of about 40,000 tonnes per annum delivered 30-300% of the aeolian iron flux due to terrestrial dust and about 20% of the upwelled iron flux in the Southern Ocean. Ombrotrophic peatlands, such as those found on Macquarie Island, which receive inputs of material solely from the atmosphere, provide especially useful records of cosmic dust deposition over the Holocene.
Taken from the 2009-2010 Progress Report:
Progress against objectives:
Peat core samples were collected on Macquarie Island in April 2010. These samples will be analysed over the coming year.
Data Set Citation
Dataset Originator/Creator: Cropp, R.
Dataset Title: An assessment of variability in the influx of cosmic dust during the Holocene and the potential effect on iron concentrations in the Southern Ocean.
Dataset Series Name: CAASM Metadata
Dataset Publisher: Australian Antarctic Data CentreOnline Resource: https://data.aad.gov.au/aadc/metadata/metadata_redirect.cfm?md=/AMD...
Start Date: 2010-04-02Stop Date: 2010-04-12
Quality Values provided in temporal and spatial coverage are approximate only.
These data should also be used with caution - the carbon dating suggests that there may have been some sort of movement in the peat - slumping and overlaying perhaps, or some error in the sampling - unfortunately the scientist responsible for the carbon dating has passed away, so while we can be confident in the actual data, using the cores to reconstruct what has happened over time would be dangerous.
Access Constraints These data are publicly available for download from the provided URL.
Use Constraints This data set conforms to the PICCCBY Attribution License
Please follow instructions listed in the citation reference provided at http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=AAS_3132 when using these data.
Data Set Progress
Distribution Media: HTTP
Distribution Size: 48 kb
Distribution Format: csv
Role: TECHNICAL CONTACT
Phone: +61 7 3735 4036
Fax: +61 7 3735 7459
Email: r.cropp at griffith.edu.au
Griffith University School of the Environment 170 Kessels Road
Province or State: QLD
Postal Code: 4111
Role: DIF AUTHOR
Phone: +61 3 6232 3244
Fax: +61 3 6232 3351
Email: dave.connell at aad.gov.au
Australian Antarctic Division 203 Channel Highway
Province or State: Tasmania
Postal Code: 7050
Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2010-07-06
Last DIF Revision Date: 2014-10-16