A Holocene subtropical hydroclimate reconstruction from Karboora (Blue Lake), Minjerribah, Queensland

Holocene palaeoclimatology provides insights into the climate system, with particular relevance to the next century. This is especially true in sub-tropical Australia due to the under representation of the region in Holocene climate studies. Karboora (Blue Lake), on Minjerribah (North Stradbroke Island), Queensland, Australia is a groundwater window lake of major ecological and cultural significance. The lake’s strong connection with the regional aquifer underpins lake level stability, rendering Blue Lake sediments an ideal tracer of subtle changes in climate. Here, we report a new 5,500-year oxygen isotope record from biogenic (diatom) silica (δ18OBSi) that records variations in rainfall resulting from changes in Pacific atmospheric circulation. These interpretations are supported by modern monitoring over a 20 month period, including the δ18O of lake water, rain water, plant cellulose, and biogenic silica. We link rain δ18O to changes in El Niño Southern Oscillation (ENSO) phases, with phases showing distinct isotopic change that may be linked to tropical or extratropical sources of rainfall. On these grounds, we infer a dominance of extratropical rainfall from 5.5 kyr BP to 3.5 kyr BP, a period of transition from 3.5 kyr BP to 2.5 kyr BP dominated by neither tropical or extratropical rainfall, then a shift to tropically sourced rain from 2.5 kyr BP to the present. The early record (5.5 kyr BP – 3.5 kyr BP) most likely reflects a suppression of summer rainfall caused by a weakened ENSO. This is most likely linked to higher northern hemisphere insolation causing a northward shift in the intertropical convergence zone and westerly wind belt which in turn affected synoptic systems in the Coral and Tasman Seas. The increasing variability in the late record (3.5 kyr BP to present) most likely represents an increase in summer rainfall driven by the intensification of ENSO in the late Holocene.

Keywords

Quaternary period, Queensland, Climates, Lakes, Ground water, Oxygen isotopes, Water, Rain water, Southern Oscillation, Ecology, Tasman Sea

Citation

Maxson C., Tibby, T., Tyler, J., Marshall, J., McGregor, G., Schulz, C., Jacobsen, G., & Klaebe, R. (2022). A Holocene subtropical hydroclimate reconstruction from Karboora (Blue Lake), Minjerribah, Queensland. Paper presented to AQUA 2022 Conference, 6-8 December 2022, Adelaide. (pp. 71-72). Retrieved from: http://aqua.org.au/wp-content/uploads/2022/11/AQUA-2022-conference-program-and-abstract-booklet.pdf

URI

http://aqua.org.au/wp-content/uploads/2022/11/AQUA-2022-conference-program-and-abstract-booklet.pdf
https://apo.ansto.gov.au/handle/10238/15540

Collections

Conference Publications

Full item page