Fast-changing upwelling off the west coast of Hainan Island

Journal Pre-proof Fast-changing upwelling off the west coast of Hainan Island Peng Bai, Zheng Ling, Shuwen Zhang, Lingling Xie, Jingling Yang

PII: DOI: Reference:

S1463-5003(19)30186-6 https://doi.org/10.1016/j.ocemod.2020.101589 OCEMOD 101589

To appear in:

Ocean Modelling

Received date : 18 June 2019 Revised date : 8 February 2020 Accepted date : 10 February 2020 Please cite this article as: P. Bai, Z. Ling, S. Zhang et al., Fast-changing upwelling off the west coast of Hainan Island. Ocean Modelling (2020), doi: https://doi.org/10.1016/j.ocemod.2020.101589. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Elsevier Ltd. All rights reserved.

Journal Pre-proof 1

Fast-changing upwelling off the west coast of Hainan Island

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Peng Bai a, b, Zheng Ling a, Shuwen Zhang c, Lingling Xie a, b, Jingling Yang a, b, *

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a

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College of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang, China

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b

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China

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c

Institute of Marine Sciences, Shantou University, Shantou, China

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*

Corresponding author at: Guangdong Province Key Laboratory for Coastal Ocean Variation and

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Disaster Prediction, College of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang,

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Guangdong Province Key Laboratory for Coastal Ocean Variation and Disaster Prediction,

Southern Marine Science and Engineering Guangdong Laboratory (Zhanjiang), Zhanjiang,

China. E-mail address: [email protected] (J. Yang).

11 Highlights

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Upwelling off the west coast of Hainan Island (UWH) can change rapidly.

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•

Vigorous horizontal advection and high vertical velocity due to tidal waves.

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•

Effect of weak tidal flow on UWH weak during neap tide or tidal current

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transition.

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Abstract In this study, we investigated the short-term dynamics of upwelling off the

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west coast of Hainan Island (UWH) by combining Moderate Resolution Imaging

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Spectroradiometer (MODIS) infrared sea surface temperature (SST) images and

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Regional Ocean Modeling System (ROMS) simulations. MODIS observations showed

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that the UWH could exhibit rapid temporal variations, where the SST could increase or

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decrease by more than 1 °C within 3 h. Further investigations based on ROMS

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Journal Pre-proof simulations suggested that flood tides could rapidly intensify the UWH, whereas ebb

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tides could rapidly weaken the UWH. Strong horizontal advection by intense tidal

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currents and high vertical velocity due to divergence/convergence triggered by

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progressive tidal waves were identified as the intrinsic physical mechanisms

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responsible for the rapid SST variations in the UWH. These findings were verified

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based on a MODIS-observed fast-cooling UWH event and a MODIS-observed

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fast-warming UWH event. Analyses of the timing of occurrence, tidal phase, and

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spatial patterns of the significant variations in the SST for these events all agreed with

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the hypothesis stated above. Model–data fusion analysis indicated that when a neap tide

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or transition period for tidal currents occurs, the influence of the tidal flow on the UWH

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is

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divergence/convergence.

weak

because

of

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the

associated

weak

horizontal

advection

and

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Keywords: Hainan Island, MODIS, ROMS, upwelling

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1. Introduction

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Coastal upwelling brings deep, cold, saline, and nutrient-rich waters into the euphotic

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zone, thereby facilitating the bloom of phytoplankton and other primary producers to

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benefit the growth of fish. Strong coastal upwelling systems are usually hot spots for

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fisheries, e.g., the Peru upwelling (Pauly and Christensen, 1995). As a vital

Journal Pre-proof component of the nearshore current system and a key mechanism responsible for the

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transport of various substances, coastal upwelling significantly affects the

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physicochemical environment (Ianson et al., 2009; Neumann et al., 2016; Mogollón

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and Calil, 2018), ecosystems (Quintana et al., 2015; Davis et al., 2016), bottom

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deposits (Hebbeln et al., 2000), and regional climate (Xie et al., 2003; Alves et al.,

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2018).

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The dynamics of coastal upwelling have attracted extensive attention. In general,

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Ekman transport forced by wind stress and Ekman pumping due to wind stress curl

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are recognized as the dominant drivers of most coastal upwelling systems (e.g.,

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Castelao and Barth, 2006; Jing et al., 2009; Albert et al., 2010). However, topography

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can significantly modify the coastal upwelling dynamics. Song et al. (2001)

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demonstrated that variable alongshore bathymetry facilitates the development of

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upwelling centers along the coast by enhancing (attenuating) upwelling on the

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downslope (upslope) sides of topographic highs. The uneven upwelling distribution

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induced by the topography then leads to a horizontal pressure gradient, which drives

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the meandering currents to modulate the upwelling structure (Song and Chao, 2004).

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Numerical investigations by Chen et al. (2013) suggested that a steeper shelf slope

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corresponds to a narrower cross-shore width for the surface Ekman divergence as well

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as greater vertical velocity. In addition, changes in the relative vorticity due to the

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existence of a headland or a canyon dominate the vertical motion nearby to modulate

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the local upwelling intensity (Chen et al., 2014). In addition to the wind-driven

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Journal Pre-proof mechanism, the combined effect of topography and currents can also trigger coastal

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upwelling under certain conditions (e.g., Lee et al., 1999; Allen and Hickey, 2010). In

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coastal zones, wave mixing or tide mixing can promote the uplift of lower-layer cold

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waters to enhance the upwelling intensity (Wang et al., 2015). When a river

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discharges into an upwelling zone, the water column will be stabilized by the

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freshwater, which then suppresses the growth of upwelling (Hickey et al., 2005; Wang

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et al., 2015). Moreover, coastal upwelling supplies a cold bottom boundary layer to

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the local atmosphere, which enhances the land–sea temperature gradient and adjusts

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the sea breeze circulation, and thus the upwelling varies with the changing winds,

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thereby resulting in feedback (Franchito et al., 2008; Alves et al., 2018).

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In the boreal summer, coastal upwellings that develop off the east and west

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coasts of Hainan Island are among the most distinctive hydrodynamic phenomena

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found in the northwestern South China Sea (SCS) (Fig. 1a). To the north of Hainan

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Island, a deep, narrow channel with an intense tidal flow (Shi et al., 2002) called the

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Qiongzhou Strait separates the island from the Chinese mainland. To the west, the

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Beibu Gulf is a semi-enclosed bay adjacent to the central basin of the SCS. A broad

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continental shelf of the SCS is present off the east coast of Hainan Island, with a

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depth less than 200 m and isobaths approximately parallel to the coastline (Fig. 1a).

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As shown in Fig. 1a, two upwelling zones are found around the coasts of Hainan

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Island: the upwelling off the east coast of Hainan Island (UEH) and the upwelling off

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the west coast of Hainan Island (UWH).

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Journal Pre-proof The UEH has received extensive attention in previous investigations, which

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demonstrated that the UEH is primarily a wind-driven phenomenon and it is also

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modulated by topography, river runoff, tides, wave mixing, El Niño-Southern

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Oscillation atmospheric teleconnections, and the SCS western coastal currents (Jing et

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al., 2009, 2011; Su and Pohlmann, 2009; Li et al., 2012; Su et al., 2013; Wang et al.,

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2015; Lin et al., 2016a, 2016b). The prevailing southerly winds lead to shoreward

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Ekman transport off the west coast of Hainan Island, thereby resulting in downwelling.

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However, remarkable upwelling also occurs according to both the sea surface

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temperature (SST) (Fig. 1a) and the observed vertical temperature structure (Fig. 1b),

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i.e., the UWH.

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Lü et al. (2008) proposed that the UWH is tidally driven and Fig. 1c shows a

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schematic illustration of this upwelling. During the summer, a strong tidal mixing

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front is established because of the intense tidal currents off the west coast of Hainan

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Island (Hu et al., 2003). The entire water column to the right of the front is filled with

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well-mixed warm water, whereas stratification still exists on the left side. Therefore, a

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density difference exists across the tidal mixing front, which then generates a pressure

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gradient force. Due to the topography slope, the pressure gradient force drives an

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upward motion and the UWH finally develops. The southerly winds have an

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inhibitory effect on the development of the UWH, but they are not sufficiently strong

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to suppress the UWH completely. Wang et al. (2015) and Bai et al. (2019) also

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provided support for this theory regarding the development of the UWH and

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suggested that wave mixing might play a sensitive role in this upwelling system. Despite these studies, the short-term dynamics of the UWH remain unknown

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because previous investigations focused mainly on its mean-state characteristics. Thus,

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in order to explore the short-term dynamics of the UWH, we conducted a data–model

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fusion investigation based mainly on satellite remote sensing data and simulations of

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the Regional Ocean Modeling System (ROMS). The fast-changing feature of the

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UWH and the associated physical mechanisms were clarified in detail in this study.

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The remainder of this article is organized as follows. In Section 2, we describe the

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data and tools employed. In Sections 3, 4, 5, and 6, we present the evidence,

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simulations, mechanisms, and a discussion of the fast-changing feature, respectively.

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Finally, we give our conclusions in Section 7.

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2. Data and tools

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2.1. Satellite-observed SST

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Moderate

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(http://oceancolor.gsfc.nasa.gov/) were used to capture and analyze UWH events. The

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Terra and Aqua satellites are both equipped with MODIS, and the minimum interval

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between their transit times over UWH events is approximately 3 h, which was

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suitable for determining the short-term dynamics of the UWH. To better capture the

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detailed structure of the UWH, we used MODIS Level-2 SST data with a spatial

Imaging

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Resolution

Spectroradiometer

(MODIS)

SST

data

Journal Pre-proof resolution of 1 km×1 km. MODIS cannot operate in the presence of heavy clouds,

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so we examined MODIS infrared SST images taken over the northwestern SCS

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during June to August 2001–2017 and selected the images with high quality

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observations. Furthermore, we excluded SST data with low retrieval quality flags

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(data with “qual_sst>1” were removed) to ensure the reliability of the analysis. In

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addition, we also used MODIS Level-3 monthly averaged SST data to determine the

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climatological pattern for the UWH, as presented in Fig. 1a.

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2.2. ERA-Interim winds

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We used the 3-h ERA-Interim winds data set (http://apps.ecmwf.int/datasets/) to

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capture the wind pattern that accompanied the SST results sensed by Aqua or Terra.

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The ERA-Interim data set is a global atmospheric reanalysis data set produced by the

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European Centre for Medium-Range Weather Forecasts (ECMWF) (Dee et al., 2011),

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and this product has been used extensively because of its good quality. This product

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was also used to analyze the climatological summer monsoon over the northwestern

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SCS (Fig. 1a).

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2.3. Tide model driver

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To efficiently hindcast the sea surface elevation and tidal currents, we used the Tide

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Model Driver (TMD) package supplied by Oregon State University (Egbert and

Journal Pre-proof Erofeeva, 2002). The regional tidal solutions for the China Seas (“Model_Ind_2016”),

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with a spatial resolution of 1/30° were utilized with the TMD toolbox. Both the

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TMD toolbox and tidal solutions used in this study are available from

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http://volkov.oce.orst.edu/tides/.

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3. Evidence of fast-changing UWH based on MODIS infrared SST images

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3.1. Normal diurnal variations in SST in the Beibu Gulf

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Due to the significant variations in daytime/nighttime surface solar radiation, the

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diurnal cycle is one of the most important components of the variability of the SST

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(Gentemann et al., 2003; Kennedy et al., 2007). Figures 2a–2c present the 25-h SST

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variations at stations 6215, 6238, and 6252 (locations in Fig. 1a) based on

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observations acquired by the General Oceanographic Survey of China during the

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summer of 1960. Figures 2a–2c illustrate the typical diurnal cycle of the SST in the

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central Beibu Gulf during the summer. In particular, the SST started to increase at

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6:00–9:00 when the ocean began to receive sunlight and as more solar radiation was

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absorbed, the SST reached a peak at 16:00–17:00, before then decreasing into the

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evening and the night until a new cycle started.

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Figures 2d and 2e show successive SST images acquired by MODIS on Terra at

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3:35 UTC and Aqua at 6:40 UTC on June 2, 2016, respectively. The differences in the

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SST (SSTAqua − SSTTerra) between these two observations are presented in Fig. 2f. As

Journal Pre-proof shown in Fig. 2f, the seas off the west coast of Hainan Island warmed up during the

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local daytime, which was consistent with the diurnal variation in the SST.

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Furthermore, Figs 2g and 2h show successive SST images captured by MODIS on

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Terra at 15:35 UTC and Aqua at 18:20 UTC on June 29, 2015, during local nighttime,

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respectively, and their differences are shown in Fig. 2i. The seas had just cooled down

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(Fig. 2i), which also agreed well with the diurnal variations in the SST. However, the

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MODIS infrared SST images suggested that the variations in the SST in the UWH

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disrupted the normal diurnal variations in some situations, as described in the

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following.

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3.2. Fast-changing UWH observed by MODIS SST

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Figures 3a, 3b, and 3c show successive infrared SST images captured by MODIS on

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Terra at 3:00 UTC and Aqua at 6:10 UTC on July 4, 2011, and their differences,

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respectively. Figures 3a–3c clearly indicate that the UWH intensified significantly

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within 3 h and that the SST decreased by more than 1 °C. These results contrast with

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the diurnal SST variations in the Beibu Gulf, as discussed in Section 3.1. The

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corresponding local times (UTC+8) for these two SST observations were 11:00 and

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14:10, when the solar radiation should have increased the SST during this period.

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Another example is illustrated in Figs 3d, 3e, and 3f, which show successive SST

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images captured by MODIS on Terra at 15:20 and on Aqua at 18:05 UTC on July 16,

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2003, and their differences, respectively. Remarkably, Figs 3d–3f indicate that a

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Journal Pre-proof fast-warming UWH event (increased by more than 1 °C within 3 h) occurred during

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the local nighttime when the ocean lost heat to the atmosphere and the SST should

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have decreased.

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Hence, Fig. 3 demonstrates that the UWH could exhibit fast cooling as well as

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fast warming (i.e., the UWH could change rapidly). Figures 3a and 3b also show the

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ERA-Interim winds at the nearest moments associated with the SST images, where

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they suggest that minor changes occurred in the winds during the fast-cooling UWH

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event. Similarly, the ERA-Interim wind vectors shown in Figs 3d and 3e indicate that

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a quasi-constant wind field accompanied the fast-warming UWH event. Previous

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investigations proposed that the response time for upwelling to changing winds occurs

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on a scale of several days (Gu et al., 2012; Chen et al., 2013). Moreover, the

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fast-cooling and fast-warming UWH events both contradicted the normal diurnal

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variations in the SST. Therefore, air–sea heat exchange or winds did not trigger these

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fast-changing UWH events.

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4. Modeling the fast-changing UWH

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4.1. Model configuration

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The MODIS SST images were not sufficient to determine the three-dimensional (3-D)

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structure of the fast-changing UWH. Thus, in order to better determine the intrinsic

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physics of this phenomenon, we used the ROMS model (Shchepetkin and

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Journal Pre-proof McWilliams, 2005) to simulate the 3-D dynamics of the UWH. The rectangular model

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grid extended from 105.5°E to 113.5°E in the zonal direction and from 15°N to 23°N

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in the meridional direction. Horizontally, the model had a resolution of 4 km. In the

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vertical direction, we applied a 20-level stretched terrain-following coordinate.

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Moreover, theta_s and theta_b were set to 5.0 and 0.4, respectively, to enhance the

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resolution near the surface and the bed. The topography originated from hybrid data

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based on the General Bathymetric Chart of the Oceans (GEBCO) provided by the

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British Oceanographic Data Centre (BODC; https://www.bodc.ac.uk/) and a local

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electronic navigation chart.

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Two model runs were executed to explore the short-term dynamics of the UWH:

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baroclinic and barotropic cases. For the baroclinic model, the boundary and initial

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conditions were both interpolated from the HYbrid Coordinate Ocean Model

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(HYCOM) database (https://www.hycom.org/dataserver). Tidal harmonic constants of

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10 tidal constituents (M2, S2, N2, K2, K1, O1, P1, Q1, Mf, and Mm) derived from the

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TPXO7 product (Egbert and Erofeeva, 2002) were also added to the open boundaries

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as tidal forcing. The Comprehensive Ocean-Atmosphere Data Set (COADS05) (Da

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Silva et al., 1994) was used to generate the monthly mean surface heat and freshwater

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fluxes for the baroclinic model. Most importantly, we imposed a constant northward

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wind force of 0.035 N/m2 over the sea surface. This design was mainly based on the

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climatological wind pattern shown in Fig. 1a and the fact that winds should play a

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weak role in the fast-changing UWH, as explained in Section 3.2, which also

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Journal Pre-proof simplified the discussion. The baroclinic time step was set to 120 s, with a

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model-splitting ratio of 30, and the data output frequency was every 3 h. We

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examined the performance of the baroclinic model at modeling the UWH (not shown).

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After comparing the results produced by the baroclinic model with those reported by

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Lü et al. (2008) and Wang et al. (2015), we confirmed that the baroclinic model

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reliably simulated the 3-D dynamic structure of the UWH. The barotropic model

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shared the same tidal forcing and integration setups as the baroclinic model, but the

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salinity and temperature were kept constant throughout the integration. The baroclinic

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run and barotropic run both lasted for 120 days from their initialization, and we only

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used the outputs for the last 30 days when the model was stable.

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4.2. Tidally induced fast-changing UWH

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Diurnal tidal signals are dominant in the Beibu Gulf (Minh et al., 2014). Figures 4a–4i

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show the evolution of the SST and sea surface currents during an entire tidal period

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based on the baroclinic model. According to the simulation, the intensity of the UWH

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changed remarkably and rapidly, where it intensified during flood tides and weakened

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under ebb tidal flows. Figure 4j shows a time series of the SST along section AB

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(marked in Fig. 4a), which clearly indicates the presence of a fast-changing UWH, as

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well as suggesting that the fast-changing feature occurred during the representative

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tidal period, as shown in Figs 4a–4i, and that it was also a recurrent phenomenon.

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Journal Pre-proof Figure 4 suggests that the fast-changing UWH is closely associated with the local

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tidal phase. Moreover, the baroclinic model was run under the force of constant winds

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and monthly averaged heat fluxes, and thus Fig. 4 strongly suggests that the

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fast-changing feature of the UWH is tidally induced.

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5. Mechanism responsible for the fast-changing UWH

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5.1. Vertical structure of UWH

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The fast-changing surface structure of the UWH suggests that a corresponding 3-D

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dynamic adjustment occurs in the entire water column. We defined period T9+6

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h–T9+12 h shown in Fig. 4 as the flood tides and T9+18 h–T9+24 h as the ebb tides.

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Based on the baroclinic model, we examined the vertical distribution of the

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temperature and u-w vectors along section AB (Fig. 4a) during flood tides (Fig. 5a)

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and ebb tides (Fig. 5b). The differences in w and temperature between the flood tides

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and the entire tidal period (T9–T9+24 h) are shown in Fig. 5c, and the ebb tides and

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the entire tidal period are compared in Fig. 5d. During the flood tides, the vertical

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velocity in the UWH was remarkably intensified, with an enhancement of

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approximately 1×10,- 𝑚/𝑠, and thus the SST in the UWH zone decreased by

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approximately 1 °C (Fig. 5c). During the ebb tides, the vertical velocity exhibited an

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abnormal downward pattern (Fig. 5b), which constrained the intensity of the UWH.

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Compared with the average vertical velocity during the entire tidal period, the vertical

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velocity decreased by approximately 1×10,- m/s in the UWH under the ebb tidal

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flow, thereby leading to an increase of 1 °C in the SST (Fig. 5d). As noted in Section 1, the tidal mixing front is established by intense tidal

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currents over the western coastal seas of Hainan Island and the density difference

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across the tidal mixing front then drives the upward motion with the help of the

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topographic slope (Lü et al., 2008). However, Fig. 5b suggests that some mechanism

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must have competed with the pressure gradient force originating from the density

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difference and triggered a downward motion in UWH. The u-w vectors along section

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AB produced by the barotropic model are shown in Figs 5e and 5f for the same

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periods as those shown in Figs 5a and 5b, respectively. Figures 5e and 5f indicate that

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tides led to an upward motion in the entire water column during the flood tides and a

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downward motion during the ebb tides; therefore, this effect should account for or

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partly explain the intensified and suppressed upwellings shown in Figs 5a and 5b,

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respectively. However, how can tides significantly affect the vertical motion

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throughout the entire water column?

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5.2. Progressive tidal wave-induced convergence and divergence

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Based on the barotropic experiment, Fig. 6a shows the depth-averaged horizontal

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flood tidal flow and its divergence field, which is defined as divV5 = ∇ ∙ V5 =

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(

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∇= (

:

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,

:

:; := :

) ∙ (𝑢, 𝑣) = ,

:

:; :=

:A :;

+

:C

:=

, where V5 = (𝑢, 𝑣) is the horizontal velocity vector and

) is the two-dimensional differential operator. Figure 6a suggests that the

Journal Pre-proof progressive tidal wave could trigger a divergence/convergence train off the west coast

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of Hainan Island, and the location nearly overlapped with the UWH. Strong

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divergence/convergence of the horizontal currents led to a high upward/downward

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vertical velocity in the entire water column, as shown in Fig. 6c, which is also

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illustrated in Figs 5e and 5f. The conditions were similar during the ebb tides but the

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opposite of those during the flood tides, as suggested in Figs 6a–6d.

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Furthermore, we examined the depth-averaged horizontal currents, the

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divergence field, and the depth-mean vertical velocity for the baroclinic case during

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flood and ebb tides, where the results are shown in Figs 6e–6h, respectively. The

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results differed for the baroclinic case and the barotropic case because of the

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introduction of baroclinic effects, but the divergence/convergence train induced by

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tidal waves still existed and it induced strong upward/downward motion. As shown in

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Figs 6c, 6d, 6g, and 6h, the flood tides had a positive effect on upward motion rather

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than downward motion because the former had a stronger intensity and covered a

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broader area, i.e., the flood tides promoted the UWH. By contrast, the ebb tides had

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an inhibitory effect.

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5.3. Horizontal advection by tidal currents

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The long band-shaped UWH stretches from the southwest coast to the northwest coast

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of Hainan Island (Figs 1, 3, and 4). This band connects with cold waters toward the

Journal Pre-proof southern end of the UWH region because of upwelling off the southwest coast of

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Hainan Island (Li et al., 2018), whereas warm gulf waters exist toward the northern

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end of the UWH (Figs 1a and 4a–4i). This difference is also illustrated in Figs 6i and

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6j, which show the temperatures along section CD (Fig. 6c) during the flood and ebb

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tides.

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divergence/convergence train (also the UWH region). Given the intense tidal currents

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during both the flood tides and the ebb tides, the flood tidal currents (northward)

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could transport the southern cold waters toward the UWH region, thereby helping to

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enhance the UWH. It should be noted that a topographic slope is present at the

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18.4–18.6°N segment of section CD and this slope helps to elevate the cold water

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carried by the flow when the flood tidal currents pass, thereby enhancing the UWH.

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Under ebb tidal currents, this process transports the northern warm waters

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southwardly to the UWH area, thereby suppressing the UWH.

CD

was

specified

to

cross

the

central

axis

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Section

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323

of

the

5.4. Temperature diagnosis

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To further understand this fast-changing UWH, we diagnosed the temperature

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dynamics of the UWH based on the heat budget equation:

327 328

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FGHI

KGLM

:D

:D

:E

= −𝑢

:;

−𝑣

MLQR

MGLM :D :=

−𝑤

:D :O

+

: :O

𝐾E

:D :O

KLQR

+𝐷5 ,

with the following surface and bottom boundary conditions:

(1)

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330

: :O

: :O

𝐾E

:D

𝐾E

:D

:O

:O

OTU

=

OT,5

VWXY Z[\

=0

,

(2)

,

(3)

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where T is temperature, t is time, u, v, and w are the east–west, south–north, and

332

vertical components of the velocity, respectively, 𝐾E is the vertical diffusivity

333

coefficient, 𝑄^_` is the surface net heat flux, 𝜌 is the density of seawater, 𝐶c is the

334

specific heat capacity of seawater, and h is the water depth. The time rate of change in

335

the temperature (RATE) is on the left-hand side of Eq. (1), whereas the horizontal

336

advection term (HADV), vertical advection term (VADV), vertical diffusivity term

337

(VDIF), and horizontal diffusivity term (HDIF) are on the right-hand side. According

338

to the model diagnostics, the magnitudes of the vertical and horizontal diffusivity

339

terms are at least one order smaller than those of the other terms, and thus they were

340

not considered in this study.

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We selected two representative stations, E and F (Fig. 7a), which were located

342

adjacent to each other within the region of the divergence/convergence train. The SST

343

diagnostic terms at stations E and F are shown in Figs 7d and 7e, respectively. The

344

time series of the horizontal velocity vectors at station E during the same period is

345

presented in Fig. 7c. The complete tidal period (T9–T9+24 h) is denoted by red

346

shading and green shading for the flood and ebb tidal phases, respectively, in Figs

347

7c–7f. At station E, the VADV mainly helped to reduce the SST during the flood tides

348

and to warm the sea surface during the ebb tides (Figs 7c and 7d), which agreed well

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Journal Pre-proof with the vertical velocity patterns shown in Figs 6c and 6g, and Figs 6d and 6h,

350

respectively. The variations in the SST were basically determined by the balance

351

between the VADV and HADV, and these two terms generally had contrasting effects

352

on the UWH (Figs 7d and 7e). The magnitude of RATE at point E alternated between

353

positive and negative values regardless of the presence of flood or ebb tides, thereby

354

indicating that the relative contributions of the HADV and VADV were unclear. The

355

temperature diagnostic results at station F were similar to those at station E, but the

356

HADV and VADV had opposite signs compared with those at station E because these

357

two stations had opposite convergent signals (Figs 7a and 7b).

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349

The temperature diagnostic results were relatively chaotic at a single station, so

359

we also examined the results for the entire UWH region (dashed-lined box in Fig. 7a),

360

as shown in Fig. 7f. Figure 7f demonstrates that flood tides intensified the UWH,

361

whereas ebb tides suppressed the UWH, thereby agreeing with Figs 4a–4i. Moreover,

362

as shown in Figs 10a–10c, the areal mean SST in the UWH domain decreased during

363

the flood tidal period (marked in red) and then gradually increased during the

364

following ebb tidal period (marked in green), which are also consistent with Fig. 7f.

365

The HADV continued to decrease during the flood tides, which facilitated the

366

development of the UWH, and this supported the proposal in Section 5.3. As shown in

367

Fig. 7f, the VADV decreased from the maximum ebb flow to the maximum flood flow

368

and then increased until a new cycle began. The phase difference between the VADV

369

and HADV was approximately one quarter that of the entire tidal period. Therefore,

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Journal Pre-proof the VADV had both facilitatory and inhibitory effects on the UWH during flood tides

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and ebb tides, which were related to the dynamic adjustment of the intensity of the

372

divergence/convergence train. Near the maximum flood flow, the HADV and VADV

373

both contributed to cooling down the UWH, and the SST decreased at the fastest rate,

374

whereas the SST increased more rapidly during the maximum ebb flow (Fig. 7f). In

375

addition, the changes in the RATE, HADV, and VADV were not strictly synchronous

376

with the variations in the tidal currents, probably due to the remaining influence of the

377

last flood tides or ebb tides.

378

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6. Discussion

380

6.1. Times when fast-cooling and fast-warming UWH events occurred

381

As described in Section 3, we identified fast-cooling and fast-warming UWH events

382

based on MODIS SST observations (Fig. 3). For simplicity, we defined the start and

383

end times of the observed fast-cooling event as T5 and T6, respectively, and those of

384

the fast-warming event as T7 and T8. For the period from T5 to T6, the tidal

385

elevations and tidal currents hindcasted by the TMD at station E (Fig. 7a) are shown

386

in Figs 8e and 8f, where the locations of T5 and T6 are also marked.

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387

Figures 8e and 8f indicate that the fast-cooling UWH event occurred near the

388

maximum flood flow, which is consistent with our hypothesis and in agreement with

389

the results shown in Figs 6i and 7f. Near the maximum flood, northward tidal currents

Journal Pre-proof transported the southern cold waters to the UWH region and helped to increase its

391

intensity (negative HADV). By contrast, the vigorous upward velocity due to strong

392

divergence caused more cold water to upwell from the lower layer, which also

393

enhanced the UWH (negative VADV). Finally, the UWH cooled down rapidly under

394

the joint effect of these two factors. Furthermore, Figs 8g and 8h show that the

395

fast-warming event occurred near the maximum ebb flow, which is consistent with the

396

discussions in Sections 5.2 – 5.4. The ebb tidal flow carried the warm waters

397

southward to the UWH region and suppressed the upwelling intensity (positive

398

HADV), and the downward velocity due to the convergence of the ebb tidal flow

399

inhibited the upwelling (positive VADV), and thus the UWH warmed up significantly

400

in the related regions.

401

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390

6.2. Spatial distribution of the variations in SST

403

Figure 3c shows that the negative differences in the SST (ΔSST) during the

404

fast-cooling UWH event were located in isolated patches rather than distributed

405

continuously. To understand this distribution, Fig. 9a shows the locations of the UWH

406

at T5 and T6 by plotting the SST below 28.0 °C. According to Fig. 9a, the flood tidal

407

currents moved the location of the UWH toward the northeast, which was consistent

408

with the flow pattern. As a consequence, the hot water in area A1 (blue ellipse in Figs

409

3c and 9a) at T5 was replaced by the cold upwelling water at T6, which partly

410

explains the significantly negative ΔSST within area A1, as shown in Fig. 3c. In

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Journal Pre-proof addition, area A1 matched well with the convergent/divergent area CA (black

412

rectangle in Figs 7a, 7b, and 9a–9d), and Fig. 7d indicates that the VADV was

413

negative and this helped to intensify the UWH near the maximum flood. Therefore,

414

the upward motion in area CA due to the locally divergent flow also contributed to the

415

cold patch in area A1. Moreover, the flow divergence exhibited an alternating

416

train-like pattern (Figs 6a and 6b), and in the areas adjacent to the north and south of

417

area CA, the downward motion caused by the locally convergent flow suppressed the

418

upwelling, which might explain the isolated patchy pattern for the negative ΔSST. In

419

area A2 (red ellipse in Figs 3c and 9a), the cold upwelling waters at T5 were replaced

420

by the adjacent hot water at T6 under the influence of flood tidal currents, thereby

421

resulting in the significantly positive ΔSST in area A2 (Fig. 3c).

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411

Similarly, ΔSST was significantly positive in area A3 (red ellipse in Figs 3f and

423

9b), which was due to the joint influence of the horizontal advection of the strong ebb

424

flow and the downward motion associated with local convergence. The significantly

425

negative ΔSST in area A4 (blue ellipse in Figs 3f and 9b) was mainly due to the

426

change in the location of the UWH caused by the ebb tidal flow (Fig. 9b). In addition,

427

the fast-cooling UWH event was observed during the local daytime when the ocean

428

warmed up, and thus solar radiation may have also contributed to the significantly

429

positive ΔSST in area A2 (Fig. 3c). Similarly, the heat exchange between the ocean

430

and atmosphere (loss of heat from the ocean to the atmosphere) may have contributed

431

to the negative ΔSST within area A4 (Fig. 3f) during the local nighttime.

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Journal Pre-proof We examined the variations in the SST during the flood and ebb tides for the

433

selected tidal period presented in Fig. 4. Figure 9c shows the modeled 29.0 °C

434

isotherm at T9+6 h (red contour) and T9+9 h (green contour), and it demonstrates that

435

the location of the UWH moved northeastwardly under the flood tidal currents, which

436

is in good agreement with the satellite observations presented in Fig. 9a. Moreover,

437

Fig. 9d shows that the ebb tidal flow moved the UWH southwestward, which is also

438

consistent with the MODIS observations presented in Fig. 9b. In general, the modeled

439

UWH intensified under northward tidal currents, whereas it attenuated under a

440

southward tidal flow (Figs 9c and 9d). However, significantly positive ΔSST and

441

negative ΔSST values occurred near the southwest edge of the UWH, as shown in

442

Figs 9c and 9d, which approximately agreed with the variations in the SST in area A2

443

(Fig. 3c) and area A4 (Fig. 3f), respectively, and they were mainly due to the change

444

in the location of the UWH caused by tidal currents. Figures 9c and 9d also show that

445

the most significant ΔSST was found in area CA, which contrasted with the normal

446

diurnal variation in the SST. This result is consistent with Figs 3c and 3f, and it

447

indicates that the strong vertical velocity due to the convergence/divergence of the

448

tidal flow contributed to the variations in the SST. In addition, the modeling results

449

showed that the ΔSST values north and south of area CA had an opposite sign

450

compared with that in area CA (Figs 9c and 9d), possibly due to the opposite

451

divergence in the different areas, thereby facilitating the formation of the isolated

452

ΔSST patches shown in Figs 3c and 3f.

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Journal Pre-proof 453 6.3. Limitations of the tidal influence on UWH

455

The results presented above demonstrate the fast-changing feature of UWH and they

456

suggest that the strong vertical velocity and horizontal advection triggered by

457

progressive tidal waves might explain this fast-changing upwelling. However, these

458

suggestions are based mainly on the premise that strong tidal currents act off the west

459

coast of Hainan Island. The intensity of the tides varies with time, so we examined the

460

influence of weak tidal flow on the UWH.

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454

Figures 10a and 10b present time series of the sea level height and surface

462

velocity at station E (Fig. 7a) over approximately 30 days, where the neap tide and

463

spring tide are highlighted by cyan shading and yellow shading, respectively. The

464

area-averaged SST in the UWH domain (dashed-line box in Fig. 7a) was used as an

465

intensity index for the UWH and the time series is presented in Fig. 10c. According to

466

Figs 10a–10c, the neap tide could not trigger remarkable adjustments of the UWH in

467

the short term. This is easy to understand because during a neap tide, the tidal currents

468

and divergence/convergence of the flow are both weak, and thus the neap tide cannot

469

contribute significantly to changes in the short-term dynamics of the UWH.

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470

Figures 2d and 2e show a normal warming event in the seas off the west coast of

471

Hainan Island during the local daytime, whereas Figs 2g and 2h present a normal

472

cooling event during the local nighttime. Both events followed a diurnal SST

Journal Pre-proof variation pattern. For simplicity, we defined the start and end times of the observed

474

normal warming event as T1 and T2, respectively, and those for the normal cooling

475

event as T3 and T4, respectively. For the period from T1 to T2, the tidal elevations

476

and tidal currents hindcasted by the TMD at station E (Fig. 7a) are shown in Figs 8a

477

and 8b, respectively. Similarly, time series for the tidal elevations and tidal velocity

478

vectors during the period from T3 to T4 are presented in Figs 8c and 8d, respectively.

479

According to Figs 8a–8d, MODIS observed a normal warming event and a normal

480

cooling event that occurred during neap tides when the tidal currents were very weak,

481

as also indicated by the modeling results (Fig. 10).

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473

As shown in Fig. 11a, the SST time series observed at station 6223 during the

483

General Oceanographic Survey of China on May 30, 1959, also demonstrated that

484

neap tides could not significantly alter the short-term dynamics of the UWH. Figure

485

11a also shows time series for the tidal velocity and sea level height hindcasted by the

486

TMD during the observation period. According to Fig. 11a, the weak flood (ebb) tidal

487

currents (<0.4 m/s) during neap tides (Fig. 11b) could not break the normal diurnal

488

SST variation pattern and lead to abnormal cooling (warming) of the sea surface

489

during the local day (night), thereby demonstrating the weak role of neap tides in the

490

UWH, as also shown by the modeling results (Fig. 10).

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491

Furthermore, based on these findings, we suggest that the influence of the tides

492

on the UWH will also be weak during (or near) the transition period of the tidal flow

493

when the tidal currents are weak and the flow direction could even experience a

Journal Pre-proof reversal. Figures 12a, 12b, and 12c show the successive SST observations acquired by

495

MODIS on Terra at 3:15 UTC and Aqua at 6:15 UTC on August 2, 2005, and their

496

differences (SSTAqua − SSTTerra), respectively. For simplicity, we defined the start and

497

end times of this event as T10 and T11, respectively. The time series produced by

498

TMD for the tidal elevations and tidal velocity vectors are presented in Figs 12d and

499

12e, respectively, which show that T10 to T11 was in the transition period for the

500

tidal currents during the spring tide (Figs 12f and 12g). Therefore, Figs 12a–12g

501

suggest that even during the spring tide, the tidal currents in the transition period

502

could not alter the normal warming of the sea surface in the UWH, possibly due to the

503

weak intensity of the tidal currents and the opposite effects of flood and ebb tidal

504

flows. In addition, for the entire UWH domain, the numerical results shown in Fig. 7f

505

indicate that the RATE already changed sign (from negative to positive) before the

506

minimum flood, which also indicates the weak role of weak tidal currents during the

507

transition period.

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lP repro of

494

7. Summary and conclusion

510

The UWH is a special upwelling system given its tidally driven mechanism (Lü et al.,

511

2008; Wang et al., 2015; Bai et al., 2019). However, previous studies of the UWH

512

focused mainly on its mean-state characteristics and its short-term dynamics were not

513

investigated. In this study, we conducted a model–data fusion study using MODIS

514

infrared SST images and ROMS simulations to explore the short-term dynamics of

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Journal Pre-proof 515

the UWH. The successive MODIS SST observations acquired by the Terra and Aqua

517

satellites captured fast-cooling and fast-warming UWH events during the local

518

daytime and nighttime, respectively. The SST varied by more than 1 °C within 3 h for

519

both events, thereby suggesting that the UWH can change rapidly. Investigations

520

based on ROMS simulations demonstrated that the vigorous tidal currents in the

521

UWH domain can lead to fast and periodic adjustments in the UWH. In general, flood

522

tides intensify the UWH whereas ebb tides inhibit it. Furthermore, model–data fusion

523

analysis suggested that strong horizontal advection due to intense tidal currents and

524

high vertical velocity caused by divergence/convergence induced by progressive tidal

525

waves may comprise the intrinsic physical mechanism responsible for the

526

fast-changing UWH. We validated this hypothesis by investigating the time of

527

occurrence and the spatial distribution of the variations in the SST for the fast-cooling

528

and fast-warming UWH events. The results showed that the observations agreed with

529

the hypothesis. Finally, analyses based on MODIS SST images, in situ SST time

530

series, and model diagnostic results indicated that the influence of tidal flow on the

531

UWH is weak during the neap tides or transition periods for tidal currents, probably

532

due to the weak horizontal advection and divergence/convergence.

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516

533

The model used in this study was forced by constant winds and this

534

configuration was based on the assumption that short-term changes in winds are

535

insignificant. This assumption was reasonable and helpful for simplifying the analysis

Journal Pre-proof of the fast-changing UWH. However, winds can sometimes change significantly

537

within a short time but their effects have not been determined. This study

538

demonstrated that the UWH can be fast-changing and we provided reasonable

539

explanations in order to obtain a better understanding of the UWH. In future research,

540

it would be interesting to identify the different roles as well as the joint effects of

541

variable winds and tides on the UWH dynamics.

542

lP repro of

536

Acknowledgments

544

This study received joint support from the Program for Scientific Research Start-up

545

Funds of Guangdong Ocean University (no. 101302/R18001), the Fund of Southern

546

Marine Science and Engineering Guangdong Laboratory (Zhanjiang) (no.

547

ZJW-2019-08), the National Key Research and Development Program of China (no.

548

2016YFC1401403), the National Natural Science Foundation of China (no.

549

41776034), and the First-class Discipline Plan of Guangdong Province (no.

550

CYL231419012). We thank NASA for providing the MODIS SST data

551

(http://oceancolor.gsfc.nasa.gov/), BODC for providing the GEBCO bathymetry data

552

(https://www.bodc.ac.uk/), and ECMWF for supplying the ERA-Interim product

553

(http://apps.ecmwf.int/datasets/).

We

554

(http://volkov.oce.orst.edu/tides/)

and

555

(https://www.myroms.org/). We also gratefully acknowledge the constructive and

556

insightful comments from two anonymous reviewers, and the professional edits from

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thank the

the

TMD

developers

of

team ROMS

Journal Pre-proof 557

the journal language editor.

lP repro of

558 559

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Continental Shelf Research, 113, 47–61.

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Pauly, D., Christensen, V. (1995). Primary production required to sustain global fisheries. Nature, 374(6519), 255.

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Quintana, C.O., Bernardino, A.F., de Moraes, P.C., Valdemarsen, T., Sumida, P.Y.

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(2015). Effects of coastal upwelling on the structure of macrofaunal communities

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in SE Brazil. Journal of Marine Systems, 143, 120–129.

Journal Pre-proof Shchepetkin, A.F., McWilliams, J.C. (2005). The regional oceanic modeling system

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(ROMS): a split-explicit, free-surface, topography-following-coordinate oceanic

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model. Ocean Modelling, 9(4), 347–404.

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Shi, M., Chen, C., Xu, Q., Lin, H., Liu, G., Wang, H., Wang, F., Yan, J. (2002). The

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role of Qiongzhou Strait in the seasonal variation of the South China Sea

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circulation. Journal of Physical Oceanography, 32(1), 103–121.

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Song, Y.T., Haidvogel, D.B., Glenn, S.M. (2001). Effects of topographic variability on

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the formation of upwelling centers off New Jersey: a theoretical model. Journal

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of Geophysical Research: Oceans, 106(C5), 9223-9240.

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Song, Y.T., Chao, Y. (2004). A theoretical study of topographic effects on coastal upwelling and cross-shore exchange. Ocean Modelling, 6(2), 151–176.

Su, J., Pohlmann, T. (2009). Wind and topography influence on an upwelling system

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at the eastern Hainan coast. Journal of Geophysical Research: Oceans, 114(C6),

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C06017. https://doi.org/10.1029/2008JC005018.

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Su, J., Xu, M., Pohlmann, T., et al. (2013). A western boundary upwelling system

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response to recent climate variation (1960-2006). Continental Shelf Research, 57,

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3–9.

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Wang, D., Yang, Y., Wang, J., et al. (2015). A modeling study of the effects of river

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runoff, tides, and surface wind-wave mixing on the eastern and western Hainan

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upwelling systems of the South China Sea, China. Ocean Dynamics, 65(8),

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1143–1164.

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Xie, S.P., Xie, Q., Wang, D., Liu, W.T. (2003). Summer upwelling in the South China

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Sea and its role in regional climate variations. Journal of Geophysical Research:

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Oceans, 108(C8), 3261.

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690 Fig. 1. (a) Climatological summer sea surface temperature (SST) (based on Moderate

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Resolution Imaging Spectroradiometer (MODIS) monthly mean SST data and

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averaged over June to August 2000–2014) and winds (derived from the ERA-Interim

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3-h wind product and averaged over June to August 1979–2014) around Hainan

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Island, where the gray contours are the isobaths. (b) Vertical temperature structure

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along section J52–J56 observed from July 15 to August 7, 2006 (following Chen et al.,

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2009). (c) Schematic sketch of the tidally driven upwelling off the west coast of

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Hainan Island (UWH) (adapted from Wang et al., 2015), where the dashed lines

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indicate the isotherms.

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Fig. 2. Diurnal variations in the sea surface temperature (SST) at stations 6215 (a),

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6238 (b), and 6252 (c) during the summer of 1960. Successive SST observations

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acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra

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at 3:35 UTC (d) and Aqua at 6:40 UTC (e) on June 2, 2016 and their differences

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(SSTAqua − SSTTerra) (f). (g)–(i) Successive SST observations acquired at 15:35 UTC

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and 18:20 UTC on June 29, 2015, by MODIS on Terra and Aqua, respectively, and

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the differences between them.

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Fig. 3. Successive sea surface temperature (SST) observations acquired by the

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Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra at 3:00 UTC (a)

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Journal Pre-proof and Aqua at 6:10 UTC (b) on July 4, 2011 and their differences (SSTAqua−SSTTerra) (c).

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(d)–(f) Successive SST images acquired at 15:20 UTC and 18:05 UTC on July 16,

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2003, by MODIS on Terra and Aqua, respectively, and their differences. The arrows

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superimposed on the SST show the wind vectors at the nearest moments based on the

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ERA-Interim wind product. Only differences exceeding ±0.4 °C are plotted for (c)

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and (f).

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Fig. 4. (a)–(i) Baroclinic model-simulated sea surface temperature (SST)

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superimposed with surface currents over a complete tidal period, where the red

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contours indicate the 29 °C isotherms. (j) SST time series along section AB marked in

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(a), where “T9” corresponds to the time of occurrence for (a).

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Fig. 5. Baroclinic model-simulated temperature superimposed with the u-w vectors

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along section AB during flood tides (a) and ebb tides (b), where the white contours

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indicate the 29 °C isotherms. (c) Differences in the w velocity (colored shading) and

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temperature (black lines) between the flood tides (T9+6 h–T9+12 h) and the average

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for the whole tidal period (T9–T9+24 h). (d) The same as (c) but for comparisons

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between the ebb tides (T9+18 h–T9+24 h) and the average for the whole tidal period.

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(e) and (f) The u-w vectors modeled by the barotropic model along section AB at the

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same time as those in (a) and (b), respectively. The w velocity was amplified 1000

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times to plot the u-w vectors.

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Fig. 6. Barotropic model-produced depth-averaged horizontal currents (arrows) and

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the divergence field (color maps) during flood tides (a) and ebb tides (b). (c) and (d)

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Journal Pre-proof Depth-mean vertical velocities corresponding to flood tides and ebb tides, respectively.

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(e), (f), (g), and (h) The same as (a), (b), (c), and (d), respectively, but for the

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baroclinic case. Temperature superimposed with the w velocity along section CD

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(marked in Fig. 6c) for the flood (i) and ebb (j) tides, where the solid black contours

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indicate positive vertical velocity, whereas the dashed purple lines indicate negative

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vertical velocity. The w velocity was amplified 1000 times.

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Fig. 7. Barotropic model-produced divergence field of the depth-averaged horizontal

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flood (a) and ebb (b) tidal currents, where the red contour denotes the monthly mean

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29 °C isotherm. Stations E and F were located adjacent to each other within the region

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of the divergence/convergence train. The dashed-lined box indicates the upwelling off

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the west coast of Hainan Island (UWH) domain. (c) Horizontal velocity time series at

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station E. (d) and (e) Time series of the sea surface temperature (SST) diagnostic

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terms at stations E and F, respectively. (f) Spatially averaged time series of the SST

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diagnostic terms in the UWH domain (dashed-lined box in Fig. 7a). HADV,

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horizontal advection term; RATE, rate of change in temperature; VADV, vertical

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advection term.

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Fig. 8. Time series of the tidal elevations (left column) and currents (right column)

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produced by the Tide Model Driver (TMD) at station E (Fig. 7a) for the period of the

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normal warming upwelling event off the west coast of Hainan Island (UWH event) in

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Figs 2d–2f (a and b), the normal cooling UWH event in Figs 2g–2i (c and d), the

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abnormal fast-cooling UWH event in Figs 3a–3c (e and f), and the abnormal

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Journal Pre-proof fast-warming UWH event in Figs 3d and 3e (g and h). SLH, sea level height.

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Fig. 9. (a) Distributions of sea surface temperature (SST) below 28.0 °C during the

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fast-cooling upwelling event off the west coast of Hainan Island (UWH event). The

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arrows denote the surface tidal currents hindcasted by the Tide Model Driver (TMD)

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at (T5+T6)/2. (b) SST locations below 28.8 °C during the fast-warming UWH event.

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The arrows denote the surface tidal currents hindcasted by the TMD at (T7+T8)/2. (c)

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SST differences (color shadings) modeled by the baroclinic model between T9+6 h

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and T9+9 h during the flood tides. The red contour shows the 29.0 °C isotherm at

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T9+6 h and the green contour shows that at T9+9 h. The arrows denote the mean

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surface velocity vectors between T9+6 h and T9+9 h. (d) Similar to (c) but showing

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the information for T9+21 h and T9+24 h during the ebb tides.

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Fig. 10. Time series of the sea level height (SLH) (a) and surface velocity (b) at

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station E (Fig. 7a) over approximately 30 days. (c) Time series of the areal mean sea

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surface temperature (SST) in the upwelling off the west coast of Hainan Island (UWH)

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domain (dashed-lined box in Fig. 7a).

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Fig. 11. (a) Sea surface temperature (SST) time series (red line; red rhombuses show

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the raw data) observed at station 6223 and time series for tidal velocity (arrows) and

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sea level height (SLH) (blue line) hindcasted by the Tide Model Driver (TMD). (b)

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Longer time series of tidal velocities at station 6223 hindcasted by the TMD. Note

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that all times are UTC times and the observation period is highlighted in cyan in (a)

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and (b).

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Journal Pre-proof Fig. 12. Successive sea surface temperature (SST) observations acquired by the

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Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra at 3:15 UTC (a)

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and Aqua at 6:15 UTC (b) on August 2, 2005 and their differences (SSTAqua − SSTTerra)

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(c). Time series of tidal elevations (d) and currents (e) produced by the Tide Model

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Driver (TMD) for the T10 to T11 period. (f) and (g) Longer time series of tidal

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elevations and currents. The period from T10 to T11 is highlighted in red in (d)–(g).

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SLH, sea level height.

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Journal Pre-proof Declaration of interests

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☒ The authors declare that they have no known competing financial interests or personal

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relationships that could have appeared to influence the work reported in this paper.

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☐ The authors declare the following financial interests/personal relationships which may be

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considered as potential competing interests:

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Journal Pre-proof Author Statement

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For this research article the specifying of the individual contributions of the authors is

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as follows. Bai Peng: Conceptualization, Methodology, Software, Writing - Original

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Draft, Writing - Review& Editing, Visualization. Ling Zheng: Conceptualization,

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Formal Analysis, Writing - Original Draft, Writing - Review& Editing, Visualization.

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Zhang Shuwen: Conceptualization, Methodology, Resources, Supervision. Xie

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Lingling: Conceptualization, Resources, Writing - Review& Editing. Yang Jingling:

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Conceptualization, Software, Validation, Writing - Original Draft, Writing - Review&

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Editing, Visualization.

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