Reconstruction of monsoon evolution in southernmost Sumatra over the past 35 kyr and its response to northern hemisphere climate changes

Abstract

Reconstruction of monsoon evolution in the tropical Indian Ocean and evaluation of its influence on large-scale ocean circulation and sea-air interaction processes can help us understand climate driving mechanisms. Herein, we used a gravity core SO184-10043 to present the marine sedimentary record from the southernmost Sumatra, spanning the past 35 kyr. The age model is well constrained by 12 accelerator mass spectrometry (AMS) radiocarbon dates determined in mixed planktic foraminifera. We also measured sediment grain size and major and trace elements to reconstruct the variations in hydrodynamic conditions and chemical weathering intensity. These data were then used to reveal the evolution of the northwest (Indonesian) monsoon system over the past 35 kyr. The results showed that both monsoon current and chemical weathering coincided with summer insolation in the Northern Hemisphere and responded to glacial-interglacial climate changes in the northern Atlantic. Higher grain-size values of sensitive components, increased chemical index of alteration (CIA), and Ba/Sr ratios, together with lower CaO/MgO ratios, reflect a stronger monsoon current and chemical weathering during the late marine isotope stage 3 and Holocene. Higher intensity of chemical weathering might be attributed to a stronger northwest monsoon carrying warm and moist air from the Asian continent to Indonesian waters. Lower values of sensitive components, CIA, and Ba/Sr, along with higher CaO/MgO values, reveal a weaker monsoon current and lower intensity of chemical weathering during the last glaciation-deglaciation phase, which was controlled by a weaker monsoon system. At a millennial timescale, cold events occurred during the following intervals: 30–26 ka BP, Heinrich Stadial 1 (HS1; 18–15 ka BP), Last Glacial Maximum (LGM; 23–18 ka BP), Younger Dryas (YD; 11–10 ka BP), and 8.2 ka BP. The same cold events were identified from core SO184-10043, indicating a perfect match with climatic cooling in the Northern Hemisphere. We also observed periodicities of ~ 7.9 ka, 3.0–3.1 ka, 2.2–2.3 ka, and ~ 1.0 ka in our core records. These periodicities are coincident with solar-induced climate changes and support the hypothesis that monsoon evolution in the tropical Indian Ocean during the late Pleistocene coincided with the climate change in the Northern Hemisphere.

Deep phylogeographic splits and limited mixing by sea surface currents govern genetic population structure in the mangrove genus Lumnitzera (Combretaceae) across the Indonesian Archipelago

“…While the latter connects the Western Pacific and the Indian Ocean and coincides with Wallace's line, seasonal, weather‐driven surface currents likely are more important for dispersal of the buoyant seeds of mangroves. The well‐known sea surface currents that flow during the Northwest (NW) Monsoon (January to March) and the Southeast (SE) Monsoon (May to November) have evolved over the past 35 kyr as part of the monsoon system in Indonesian seas (Liu et al, 2020) and generate dynamic seawater movements across the Indonesian Archipelago (Gordon et al, 2003; Fallon & Guilderson, 2008; Sprintall et al, 2019). In particular, they connect East and West and partly run northward into the Makassar Strait, therefore making Wallace's line permeable (Wainwright et al, 2018).…”

Dinamika Muka Laut Di Pesisir Kabalutan, Teluk Tomini

“…Skenario untuk simulasi prediksi kenaikan muka air laut diturunkan dari dokumen laporan sintesis IPCC (2007) dengan penambahan beberapa asumsi terkait dengan pemilihan pilot lokasi kajian. Skenario dari IPCC tersebut juga diacu oleh Perdinan et al (2017), yang hingga kini masih relevan (Li et al 2016;Liu et al, 2020). Asumsi yang diambil tersebut antara lain: belum melibatkan parameter geodinamika seperti kemungkinan adanya Uplift dan/atau Land Subsidence dalam kurun waktu 2012-2037 secara kontinyu setiap tahun; juga tidak melibatkan parameter gelombang akibat angin (wind waves); dan di Kabalutan bukan suatu zona industri dan tidak terdapat PLTU yang membuang limbah air panas ke laut, sehingga apabila terjadi pemanasan global sedikit dimungkinkan berdampak kepada kenaikan muka air laut di Kabalutan (Brodjonegoro et al, 2004;Supangat & Pranowo, 2013).…”

Last Deglaciation—Holocene Australian-Indonesian Monsoon Rainfall Changes Off Southwest Sumba, Indonesia

“…A study on AIM past changes is significant to generate robust analogs as the basis to predict and model AIM rainfall future changes [3,4]. Previous studies from both marine and non-marine proxies in the AIM region (Southern Indonesia and Northern Australia) suggested millennial -multi-millennial scale changes of AIM during the Last Glacial Maximum (LGM)-Holocene [1,[5][6][7][8][9][10]. Based on modern conditions as analog, drier (wetter), or lower (higher) rainfall conditions characterizes the Australian-Indonesian winter (summer) monsoon intensification [2,11].…”