International Journal of Oceans and Oceanography ISSN 0973-2667 Volume 14, Number 2 (2020), pp. 197-220 © Research India Publications https://dx.doi.org/ Centennial-Millennial Climate Variability in the Makassar Strait during Early Holocene until the End of the Last Deglaciation Marfasran Hendrizan1,3*, Nining S. Ningsih2, Sri Y. Cahyarini3, Mutiara R. Putri2, Bambang Setiadi4, Iwan P. Anwar1,2, Dwi A. Utami3, Vera C. Agusta3 1 Earth Sciences Study Program, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Labtek XI, Jl. Ganeca No. 10, Bandung 40132, Indonesia. E-mail: m_hendrizan@yahoo,com (MH); [email protected] (IPA) 2 Research Group of Oceanography, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Labtek XI, Jl. Ganeca No.10, Bandung 40132,Indonesia. E-mail:[email protected] (NSN), [email protected] (MRP) 3Paleoclimate and Paleoenvironment Research Group, Research Center for Geotechnology, Indonesian Institute of Sciences, Jl. Sangkuriang Bandung 40135, Indonesia. E-mail:[email protected] (SYC), [email protected] (DAU), [email protected] (VCA) 4Geoinformatics and Computations Research Group, Research Center for Geotechnology, Indonesian Institute of Sciences, Jl. Sangkuriang Bandung 40135, Indonesia. E-mail: [email protected] *Correspondence: [email protected] Abstract Indonesian archipelago establishes an essential region for considering relationships between climate and human activities in the region. However; large uncertainties remain in understanding Indonesian hydroclimate under varying timescales. Here we present reanalyzed data of high-resolution proxy from high sedimentation rate (120-170 cm/kyrs) marine sediment core SO217- 18517 from 9 to 14 kyrs in the offshore Mahakam Delta. Our dataset reveals high-frequency variations at centennial and millennial time scales during the 18 period between 9 and 14 kyrs based on multi-proxies data (δ Osw; Sea Surface Temperature/SST; and δ18O). Early Holocene to the end of last deglaciation period in the Makassar Strait was characterized by mixture forcing between 198 Marfasran Hendrizan et al. deep ocean and solar radiation with ~1100 and ~1000-years periodicity in 18 18 altering millennial-scale variability on δ Osw and δ O records. On centennial timescale; the Makassar Strait climate variability was dominated by ~500-years periodicity recorded for Sea Surface Temperature (SST) at our core site location which is more influenced by deep ocean circulation. Keywords: Centennial; Millennial; Mixture Forcing; Deep Ocean, Solar Radiation; Makassar Strait 1. INTRODUCTION Climate variability in the Indonesian archipelago may have played a confidence role on the intensity of rainfall patterns and tropical convections in the highly populated region related to global warming impact in the future. Precipitation patterns in the Indonesian archipelago are strongly governed by island topography and/or ocean-atmosphere interactions. The phase five of Coupled Model Intercomparison Project (CMIP5) climate model predicts Southern Hemisphere monsoon including Indonesia will get less precipitation in the future (Lee & Wang, 2014). However, large uncertainties remain in understanding Indonesian hydroclimate under different timescales in the past. Therefore, it is crucial to study hydrologic variability in the Indonesian archipelago and dynamic process on a wide range spatial and temporal timescales. Holocene climate archived have been identified centennial to millennial-scale in tropical region (Khider et al., 2014). It is also challenging to look further those centennial to millennial-scale climate into the last deglacial period in the tropical region. Examples of millennial-scale variability such as the Heinrich Stadial 1 (HS1), Bølling-Allerød (B-A) and the Younger Dryas (YD) exist in the Indonesian region which is associated with precipitation changes in the region (Hendrizan et al., 2017; Kuhnt et al., 2015). However, centennial to millennial-scale variability of Indonesian hydroclimate since the last deglaciation until the early Holocene might be controlled by more than single forcing on tropical rain belt changes (Hendrizan et al., 2017). Southward swings of the Intertropical Convergence Zone (ITCZ) (Hendrizan et al., 2017; Kuhnt et al., 2015; Muller et al., 2008), El Niño Southern Oscillation (ENSO) changes (Levi et al., 2007; Stott et al., 2004), and sea level (Griffiths et al., 2009; Partin et al., 2007) are likely mechanisms in controlling precipitation changes at Indonesian region. The questions will be appeared, do centennial to millennial-scale climate variability occur in the Indonesian region during the last deglaciation and the Holocene? What is the main forcing on precipitation changes in the Indonesian region? we will extend the strength of the Atlantic Meridional Overturning Circulation (AMOC) proposed by previous study (Khider et al., 2014) which may influence the ocean/atmosphere system on centennial-millennial timescales in the Indonesian region. Centennial-Millennial Climate Variability in the Makassar Strait… 199 In addition, solar forcing is also identified in the Holocene period as an external forcing (Bond et al., 2001; Debret et al., 2009). However, recent study mentions Holocene centennial to millennial-scale variability might be controlled by deep water circulation in the western Pacific region (Khider et al., 2014) or ocean-ice sheet interaction (Bakker et al., 2017) as an internal forcing. Both external and internal forcing could trigger heat transfer in the Indonesian region which can be traced in the longer period until the last deglacial period in the region. Several marine sediment cores in the Indonesian region record a long temporal resolution until the last deglaciation in understanding the influence of Sea Surface Temperature (SST) with regional climate in the region (Mohtadi et al., 2011, 2017; Schroder et al., 2016; Schröder et al., 2018; Visser et al., 2003). Core SO217-18517 (Hendrizan et al., 2017) is more challenging to be reanalyzed due to the influence of river runoff and the ITF intensity in the core site. In addition, the core provides the highest resolution timescales until < 7 years during the last 18 deglacial period. δ Osw records in the Makassar Strait (Fan et al., 2013) interpreted millennial-scale variability during Holocene controlled by ENSO variability. Other revealed deep sea circulation is the main forcing of millennial-scale variability in the West Pacific Warm Pool (WPWP) during Holocene (Khider et al., 2014). Different forcing on millennial-scale variability in the WPWP especially central Indonesia is still 18 open question related to complex influences of δ Osw in the central Indonesia (Schröder et al., 2018). One of the most important is local river input which local river 18 input is known to be an important factor in controlling δ Osw – salinity variability in the WPWP (Katz et al., 2010; Morimoto et al., 2002). Therefore, Core SO217-18517 closes to the Mahakam River is suitable to understand high resolution climate signal in the Makassar Strait. Here we present high-resolution proxy data from high sedimentation rate (120-170 cm/kyr) marine sediment core SO217-18517 from 9 to 14 kyr in the offshore Mahakam Delta ((Hendrizan et al., 2017); Figure 1). The previous study (6) in Core SO217-18517 has not explained whether similar or not the Younger Dryas climate mechanisms in the Makassar Strait with the early Holocene period. Previously, uneven time series of Core SO217-18517 based on multi-proxies analysis was reported in (Hendrizan et al., 2017). In this study we have improved the evenness of the time series to 10 years/sample resolution, and concentrated on the time period 9 to 14 kyr. We present multi-proxies 18 18 (δ O, SST, δ Osw) wavelet analysis of Core SO217-18517 to characterize centennial and millennial climate variability spanning from early Holocene and the end of the last deglaciation in the Makassar Strait. We compare our multi-proxies data with other hydroclimate records in the central Indonesia particularly Kalimantan and Sulawesi region. 200 Marfasran Hendrizan et al. Figure 1. a. Location of core SO217-18517 (1°32.198’S, 117°33.756’E; 698 m water depth), off Mahakam Delta, East Borneo (modificafion Figure from Supp. Figure 1 in (Hendrizan et al., 2017)). Red stars indicates core locations from other studies, marine sediment cores SO217-18519 and TGS-931 (Schröder et al., 2018), SO217-18515 (Schroder et al., 2016), Lake sediment from Towuti (Konecky et al., 2016), and Gunung Buda speleothem (Partin et al., 2007) in a bathymetric map from ETOPO 1 (http://maps.ngdc.gov/viewer/bathimetry); b. Marine sediment photograph of Core SO217-18517 in-depth scale. 2. REGIONAL CLIMATE AND OCEANOGRAPHY Marine sediment core SO217-18517 (1°32.198’S, 117°33.756’E; 698 m water depth) is situated in the offshore Mahakam Delta, East Borneo (Hendrizan et al., 2017) which extends for about ~90 km from the coastal line (Figure 1). The core was collected as a part of the SO217 (Makassar-Java/MAJA) cruise using R/V Sonne. The core site is connected to the southeast distributary channel of the Mahakam River. However, the core site is not only influenced by Mahakam river runoff but also controlled by lower thermocline Indonesian Throughflow (ITF) ((Hendrizan et al., 2017); Figure 1). During boreal summer, the changes in wind direction shift towards Asia due as the Intertropical Convergence Zone (ITCZ) moves northward, leading to reduced precipitation