Browsing by Author "Jones, MD"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    A detailed study of Holocene climate variability in south-east Australia based on cellulose inferred lake water isotopes and monitoring and modelling approach at Lake Surprise, western Victoria.
    (Australasian Quaternary Association Inc., 2022-12-06) Dharmarathma, A; Tyler, JJ; Tibby, J; Barr, C; Cadd, H; Ankor, MJ; Jones, MD; Tadros, CV; Hua, Q; Child, DP; Zawadzki, A; Hotchkis, MAC; Gadd, PS; Klaeb, RM; Hall, T
    During the Holocene, southeast Australia experienced intense climate conditions including extended droughts. However, knowledge of the frequency and intensity of such episodes is restricted due to the scarcity of quantitative, high-resolution climate records from the region. Where conditions are possible, oxygen isotopes preserved in lake sediments are a useful tool for retracing the past climatic and environment. Here we present a well-dated, highly resolved Holocene record based on δ18O values of aquatic cellulose, alongside organic carbon isotopes and carbon/nitrogen ratios from sediments at Lake Surprise in western Victoria. Our interpretation of the palaeo-data is supported by both monitoring of water and sediment accumulation and lake isotope mass balance modelling to track the modern hydrology of the lake. The lake is highly groundwater dependant alongside its evaporative enrichment of major ions and stable isotopes. The cellulose record indicates a trend of gradually increasing aridity towards the present day, with notable extreme wet periods prevailing from 10900 – 10000, 7600 – 7000 and 5600 – 4500 cal yr BP. the lake represent a significant climate transition to towards aridity at 4500 cal yr BP and remained consistent over the last 4000 years, along with the driest period recorded from 2000 – 1550 cal yr BP. while our record is consistent with other studies from western Victoria, we demonstrate a strong coherence with SWW variability suggesting that the southern Ocean processes were the dominant controls of Holocene climate change at least over the study area. Further, we suggest an increasing influence of ENSO and IOD during the last two millennia. Our record also agrees with the pattern of variation in solar forcing to some extent which may symbolize a connection to proxy data and climate drivers. However, detailed analyses focused on solar activity and climate modes are required to understand teleconnections among these climate drivers and their mechanisms.
  • No Thumbnail Available
    Item
    Holocene climate variability in south east Australia; inferred from oxygen isotopes in sedimentary cellulose at Lake Surprise, Victoria
    (European General Assembly, 2022-05-23) Dharmarathna, A; Tyler, JJ; Barr, C; Tibby, J; Jones, MD; Anjor, MJ; Cadd, H; Gadd, PS; Hua, Q; Child, DP; Zawadski, A; Hotchkis, MAC; Zolitschka, B
    South east Australia experienced periods of multi-year droughts particularly within the last 2 millennia. However, given the limited evidence from smaller number of sites and scarcity of quantitative, high-resolution climate records, it is largely unknown whether these droughts are a feature of climate through the Holocene and the extent to which they are experienced throughout the region. Where conditions are suitable, oxygen isotopes preserved in lake sediments are a useful tool for reconstructing past climate and environmental conditions. Here, we present preliminary results of a Holocene length record from Lake Surprise in western Victoria, from which we analysed δ18O of aquatic cellulose as a proxy for lake-water δ18O, complemented by organic carbon/nitrogen ratios, organic carbon isotopes and XRF (ITRAX) inferred elemental composition. Our interpretation of the palaeo-data is supported by ~3 monthly monitoring of water and sediment geochemistry to track the modern hydrology of the lake. Our preliminary results show a strong positive correlation between precipitation and sedimentary calcium (carbonate deposition) over the last 150 years, likely linked to changes in primary productivity. The aquatic cellulose δ18O record through Holocene is also correlated with carbonate concentration, reinforcing our interpretation of CaCO3 deposition in the lake during wet periods. The cellulose δ18O record indicates a trend of gradually increasing aridity from early to late Holocene, with a notable extremely dry phase over the last 2 ka. Comparison of the cellulose δ18O record with high-resolution Holocene climate records indicates that multiple climate drivers such as ENSO intensification and Antarctic warming are strongly linked to increasing aridity of the region. Further work will focus on both increasing the resolution of the record to better identify the frequency and duration of key events and on quantifying natural hydroclimate variability, particularly via lake hydrologic modelling to better constrain the paleoclimate record. © Author(s) 2022. Creative Commons Attribution 4.0 Licence.
  • Thumbnail Image
    Item
    Holocene climate variability in south-eastern Australia; inferred from oxygen isotopes in sedimentary cellulose at Lake Surprise, Victoria
    (Australasian Quaternary Association (AQUA), 2021-07-08) Dharmarathna, A; Tyler, JJ; Barr, C; Tibby, J; Jones, MD; Ankor, MJ; Gadd, PS; Hua, Q; Child, DP; Zawadzki, A; Hotchkis, MAC; Zolitschka, B; Cadd, H
    During the Holocene, south-eastern Australia experienced periods of multi-year drought. However, the scarcity of quantitative, high-resolution climate records from the region means understanding of the frequency and intensity of such events is limited. Where conditions are suitable, oxygen isotopes preserved in lake sediments are a useful tool for reconstructing past climate and environmental conditions. Here, we present preliminary results from a ca. 8700 ka record from Lake Surprise in western Victoria, from which we analysed δ18O of aquatic cellulose, alongside organic carbon/nitrogen ratios, organic carbon isotopes and XRF (ITRAX) inferred elemental composition. Our interpretation of the palaeo- data is supported by ~3 monthly monitoring of water and sediment geochemistry to track the modern hydrology of the lake. Our preliminary results show a strong positive correlation between meteorological precipitation data and sedimentary calcium (carbonate deposition) over the last 150 years, likely linked to changes in primary productivity. As a proxy for lake-water δ18O, the aquatic cellulose δ18O record is also correlated with carbonate concentration, reinforcing our interpretation of CaCO3 deposition in the lake during wet periods. The cellulose δ18O record indicates a trend of gradually increasing aridity over the last 8 ka, with a notable extremely wet period ca. 7.5–7 ka and a dry period ca 2–1.5 ka. Further work will focus on increasing the resolution of the data to better identify the frequency and duration of key events and quantifying natural hydroclimatic variability, alongside continued geochemical monitoring and modelling to better constrain the interpretation of the palaeoclimate record.