The Indonesian Throughflow and the Circulation in the Banda Sea: A Modeling Study

Abstract

To investigate the relationship between the Indonesian ThroughFlow (ITF) and the Banda Sea circulation, we set up a high‐resolution ocean circulation model for the western Pacific and northern Indian Oceans. This well‐validated model demonstrates complex distributions of the along‐channel velocity in different straits, with vertically sheared flows in the Makassar and Maluku straits but horizontally sheared flows in the Halmahera, Timor, and Ombai straits. The model also reveals a three‐layer circulation pattern in the Banda Sea: clockwise, counterclockwise, and clockwise in the upper (<500 m), middle (500–2,250 m), and lower (>2,250 m) water column, respectively. The Lagrangian tracking code TRACMASS is used to diagnose the sources and sinks of Banda Sea waters. The backward/forward tracking experiment pinpoints the inflows/outflows in the straits surrounding the Indonesian Archipelago (IA), which directly affect the Banda Sea. These TRACMASS results imply active vertical exchanges in the Banda Sea, which result in fast flushing with a typical time scale of 8 years. Based on the profiles of net transport into and out of the Banda Sea estimated from the tracking experiments, the three‐layer circulations of the Banda Sea are dynamically explained in terms of the potential vorticity (PV) integral constraint: the PV flux across the boundary and the wind stress curl act in concert with approximately equal order of magnitude for the clockwise circulation in the upper layer, while the positive (negative) PV flux to the middle (bottom) layer corresponds to the counterclockwise (clockwise) circulation.

Volume and Heat Transport in the South China Sea and Maritime Continent at Present and the End of the 21st Century

“…Consequently, there are several regional ocean model‐based simulations to study SCS dynamics and Luzon transport, such as, with Modular Ocean Model version‐2 at 1/4° (Qu et al., 2004), and Princeton Ocean Model at ¼‐2° (Hsin et al., 2012; Wei et al., 2009). Of late, with the availability of better computing resources, higher resolution regional model studies have also been initiated over SCS (Fang et al., 2005; Jiang et al., 2020; Li et al., 2019; Liang et al., 2019; Liu & Gan, 2017; Nan et al., 2013).…”

“…Consequently, there are several regional ocean model-based simulations to study SCS dynamics and Luzon transport, such as, with Modular Ocean Model version-2 at 1/4° (Qu et al, 2004), and Princeton Ocean Model at ¼-2° (Hsin et al, 2012;Wei et al, 2009). Of late, with the availability of better computing resources, higher resolution regional model studies have also been initiated over SCS (Fang et al, 2005;Jiang et al, 2020;Li et al, 2019;Liang et al, 2019;Liu & Gan, 2017;Nan et al, 2013). However, all these studies are either focused on a short period of simulation, the northern SCS (e.g., Jilan, 2004), SCS-averaged layer circulation (e.g., Gan et al, 2016), the ITF region, the Kuroshio region, or different aspects of SCS that are unrelated to SCS transport.…”

The Reversal Indian Ocean Waters

“…We note the PIOM simulated mean transport of 1.8 Sv in the Ombai Strait (Liang et al, 2019) being smaller than 4.9 Sv reported by Sprintall et al (2009), but the former is a full‐depth integration of a climatological simulation, while the latter represents the 3‐year mean from surface to 1,200 m. Moreover, the observed transport bears a significant uncertainty of ~3 Sv due to interpolation schemes (Sprintall et al, 2009). We will analyze our real‐time simulation (~3.4 Sv for the same 3‐year mean, not shown) in follow‐up studies to estimate to what degree the quantitative differences might modify our conclusions.…”

Years of the Maritime Continent

“…There are many other studies motivated by YMC and addressing YMC issues using data from satellites, global reanalysis products, and numerical models. These studies cover a wide range of topics, such as the diurnal cycle (Baranowski et al, 2019), MJO propagation over the MC (Burleyson et al, 2018; Pang et al, 2018) and its barrier effect (DeMott et al, 2018; Ling et al, 2019), atmospheric waves (Ruppert & Zhang, 2019; Takasuka et al, 2019), aerosol (Bagtasa et al, 2018; Cohen et al, 2018; Koplitz et al, 2018), the monsoon (Diong et al, 2019; Duan et al, 2019), the ITF and the ocean in general (Cao et al, 2019; Gordon et al, 2019; Hu et al, 2019; Liang et al, 2019), and prediction and predictability (Wang et al, 2019).…”