Browsing by Author "Dharmarathma, A"

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    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.