Mid- to Late-Holocene Australian–Indonesian summer monsoon variability

Steinke, Stephan; Mohtadi, Mahyar; Prange, Matthias; Varma, Vidya; Pittauerova, Daniela; Fischer, Helmut W

doi:10.1016/j.quascirev.2014.04.006

Cited by 50 publications

(57 citation statements)

References 51 publications

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“…This trend is correlated with the XRF Ti/Ca signal, commonly interpreted as a detrital terrigenous advection signal through runoff and soil leaching (e.g. Bahr et al, 2005;Mollier-Vogel et al, 2013;Steinke et al, 2014). A recent study carried out on Bay of Brest modern sediments leads us to consider Alnus as a fluvial discharge indicator, based on its present-day distribution, which is correlated to river mouths (Lambert et al, 2017).…”

Section: Major Runoff Increase Over the Last 60 Yearsmentioning

confidence: 86%

Human-induced river runoff overlapping natural climate variability over the last 150 years: Palynological evidence (Bay of Brest, NW France)

Lambert

Penaud

Vidal

et al. 2018

Global and Planetary Change

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For the first time a very high resolution palynological study (mean resolution of 1 to 5 years) was carried out over the last 150 years in a French estuarine environment (Bay of Brest; NW France), allowing direct comparison between the evolution of landscapes, surface water, and human practices on Bay of Brest watersheds, through continental (especially pollen grains) and marine (phytoplanktonic microalgae: cysts of dinoflagellates or dinocysts) microfossils. Thanks to the small size of the watersheds and the close proximity of the depositional environment to the mainland, the Bay of Brest represents an ideal case study for palynological investigations. Palynological data were then compared to published palaeo-genetic analyses conducted on the same core and to various available instrumental data, allowing us to better characterize past environmental variability since the second half of the 19th century in Western Brittany. We provide evidence of some clues of recent eutrophication and/or pollution that affected phytoplankton communities and which appears linked with increased runoff (higher precipitations, higher percentages of riparian forest pollen, decline of salt marsh-type indicators, and higher values of the XRF Ti/Ca signal), mainly explained by the evolution of agricultural practices since 1945 superimposed on the warming climate trend. We assume that the significant relay observed between dinocyst taxa: Lingulodinium machaerophorum and Spiniferites bentorii around 1965 then followed by Spiniferites membranaceus after 1985, attests to a strong and recent eutrophication of Bay of Brest surface waters induced by high river runoff combined with abnormally elevated air temperatures, especially obvious in the data from 1990. The structure of the dinocyst community has thus been deeply altered, accompanied by an unprecedented increase of Alexandrium minutum toxic form at the same period, as confirmed by the genetic quantification. Despite this recent major anthropogenic forcing, the fossil pollen sequence also records natural climate variability. We highlight, for the first time, a possible connection between climate (AMO modes) and fossil pollen records (especially tree pollination rates) in coastal sediments using tree percentage fluctuations as an indirect Highlights ► High resolution palynological study (last 150 yrs) in a French estuary ► Increased runoff on mainland since 1945 ► Increased eutrophication indices since 1980 ► Changes in phytoplankton communities and increased toxic algal blooms ► Connection between AMO modes and fossil pollen records (tree pollination rates)

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Section: Major Runoff Increase Over the Last 60 Yearsmentioning

confidence: 86%

Human-induced river runoff overlapping natural climate variability over the last 150 years: Palynological evidence (Bay of Brest, NW France)

Lambert

Penaud

Vidal

et al. 2018

Global and Planetary Change

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“…They suggested that modelling results of the solar minimum at around 2,800 years BP demonstrated varied responses across the IASM region, with strengthening across Indonesia, weakening in northern Australia, and a somewhat neutral response in Borneo. It is therefore reasonable that short-term (Partin et al, 2007), d) sediment record from offshore Sumba Island, Indonesia (Steinke et al, 2014). The arrows denote in the direction of enhanced monsoon strength in the proxy record interpretation.…”

Section: Coupling Relationships Of the Iasm Regionmentioning

confidence: 88%

Transient coupling relationships of the Holocene Australian monsoon

McRobie¹,

Stemler²,

Wyrwoll³

2015

Quaternary Science Reviews

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a b s t r a c tThe northwest Australian summer monsoon owes a notable degree of its interannual variability to interactions with other regional monsoon systems. Therefore, changes in the nature of these relationships may contribute to variability in monsoon strength over longer time scales. Previous attempts to evaluate how proxy records from the IndonesianeAustralian monsoon region correspond to other records from the Indian and East Asian monsoon regions, as well as to El Niño-related proxy records, have been qualitative, relying on 'curve-fitting' methods. Here, we seek a quantitative approach for identifying coupling relationships between paleoclimate proxy records, employing statistical techniques to compute the interdependence of two paleoclimate time series. We verify the use of complex networks to identify coupling relationships between modern climate indices. This method is then extended to a set of paleoclimate proxy records from the Asian, Australasian and South American regions spanning the past 9000 years. The resulting networks demonstrate the existence of coupling relationships between regional monsoon systems on millennial time scales, but also highlight the transient nature of teleconnections during this period. In the context of the northwest Australian summer monsoon, we recognise a shift in coupling relationships from strong interhemispheric links with East Asian and ITCZrelated proxy records in the mid-Holocene to significantly weaker coupling in the later Holocene. Although the identified links cannot explain the underlying physical processes leading to coupling between regional monsoon systems, this method provides a step towards understanding the role that changes in teleconnections play in millennial-to orbital-scale climate variability.

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“…(b) Oxygen isotope data of stalagmite calcite LR06-B1 (Griffiths et al, 2009). (c) ln-ratio of Titanium and Calcium in marine core GeoB 10065-7 (Steinke et al, 2014). (d) ln-ratio of Titanium and Calcium in marine core GeoB 10053-7 (Mohtadi et al, 2011). 6e4 cal ky BP from speleothem oxygen isotope records (Partin et al, 2007), while decreasing trend was observed in western Flores at same timings (Griffiths et al, 2009: Fig.…”

Section: Regional Comparisonmentioning

confidence: 98%