Variability of Upwelling in Bone Bay and Flores Sea

International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 10, October 2018, pp. 742–751, Article ID: IJCIET_09_10_076 Available online at http://iaeme.com/Home/issue/IJCIET?Volume=9&Issue=10 ISSN Print: 0976-6308 and ISSN Online: 0976-6316

VARIABILITY OF UPWELLING IN BONE BAY AND FLORES SEA

Kunarso and Aris Ismanto Department of Oceanography, Faculty of Fisheries and Marine Science, Diponegoro University Jl. Prof. Soedarto, SH Tembalang Tlp, Semarang 50275 Center for Coastal Disaster Mitigation and Rehabilitation Studies, Diponegoro University Semarang Indonesia

Raymundus Putra Situmorang and Sri Yulina Wulandari Department of Oceanography, Faculty of Fisheries and Marine Science, Diponegoro University Jl. Prof. Soedarto, SH Tembalang Tlp, Semarang 50275

ABSTRACT The waters of Bone Bay are relatively rich in organic matter due to the phenomenon of upwelling throughout the southeast monsoon. This water is bounded by the Flores Sea in the South so that the water mass in the Bay of Bone is strongly influenced by the mass of water outside the bay, especially the Flores Sea. Upwelling is indicated by a decrease in sea surface temperature and an increase in chlorophyll- a concentration. The purpose of this study was to determine the pattern of distribution and development of upwelling areas in Bone Bay and the Flores Sea. This study uses chlorophyll-a and sea surface temperature data from MODIS satellite images Level-3 for ten years (2008-2017). The results showed that the temporal spread pattern of upwelling occurred from June to September and the peak occurred in August. Based on upwelling intensity categories in June and September are weak upwelling, July is moderate upwelling and August includes strong upwelling. Spatially spreading patterns show upwelling occurring in South Buton Island and west of Wakatobi Islands. Upwelling develops to the southwest of Buton Island as far as 73 km. The estimated upwelling area in June was around 54.59 km2 developing to the peak in August of 2090.52 km2 and in September it was reduced to 334.25 km2. Keywords: Bone Gulf, Flores Sea, Upwelling, Sea Surface Temperature, Chlorophyll-a Cite this Article: Kunarso, Raymundus Putra Situmorang, Sri Yulina Wulandari and Aris Ismanto, Variability of Upwelling in Bone Bay and Flores Sea, International Journal of Civil Engineering and Technology, 9(10), 2018, pp. 742–751. http://iaeme.com/Home/issue/IJCIET?Volume=9&Issue=10

http://iaeme.com/Home/journal/IJCIET 742 [email protected] Variability of Upwelling in Bone Bay and Flores Sea

1. INTRODUCTION Bone Bay waters are administratively located in South Sulawesi Province (to the west and north) and Southeast Sulawesi Province (to the east). The administrative area of the South Sulawesi Province bordering the waters of Bone Bay is Bulukumba Regency, Sinjai Regency, Bone Regency, Wajo Regency, Luwuk Regency, Polopo Middle City, North Luwuk Regency, and East Luwuk Regency. While the administrative area in Southeast Sulawesi Province bordering the water of Bone Bay is Bombana Regency and Kolaka Regency. The Flores Sea is the southern boundary of the waters of Teluk Bone [1]. Geographically the study area is located at coordinates 2.48o LS - 6.09o LS and 119.9o BT - 123o BT (Figure 1). Bone Bay is relatively more fertile water. The entries of low-salinity water masses from the mainland of Sulawesi Island, as well as the exchange of water masses from the Pacific Ocean to the Indian Ocean through the Sulawesi Sea, Flores Sea and the Java Sea affect the level of primary productivity in the waters of Bone Bay. The fertile waters of Bone Bay occur throughout the year both in the western season and in the east season. In the western season, high fertility rates occur due to large run-offs from the mainland of Sulawesi due to high rainfall, while in the eastern season fertilization occurs due to upwelling in the Bone Bay and Flores Sea [2]. The purpose of this study was to determine the distribution patterns and development of upwelling areas in the Bone Bay and the Flores Sea. The location of the research covers Bone Bay and the Flores Sea, shown in Figure 1.

Figure 1 Study Area. Source: Indonesian Topographic Map from Geospatial Information Agency of Indonesia, Scale 1:25,00

http://iaeme.com/Home/journal/IJCIET 743 [email protected] Kunarso, Raymundus Putra Situmorang, Sri Yulina Wulandari and Aris Ismanto

2. MATERIALS DAN METHOD

2.1. Research Material The material used in this study consisted of main data and supporting data. The main data used are Sea Surface Temperature (SST) data and chlorophyll-a data. Sea Surface Temperature and Chlorophyll-a data are obtained from Aqua MODIS (Moderate Resolution Imaging Spectroradiometer) satellite imagery. The main data are time series for a period of 10 years from 2008 to 2017. Support data used is wind data, where it is obtained from the Advanced SCATterometer (ASCAT).

2.2. Research Method The method used in this study is a quantitative method. Quantitative data collection includes SST, chlorophyll-a, and wind data. The resulting data is in the form of numbers in txt. Based on these data, it is then described in the form of SST and chlorophyll-a distribution maps. SST and chlorophyll-a distribution data are then stacked to analyze upwelling areas which have low temperature and high chlorophyll-a characteristics, this area is marked and transect, right in areas with low SST and high chlorophyll-a. Transect results are in the form of SST and chlorophyll-a values in upwelling areas. This value is then searched for maximum, minimum, mean and standard deviation. These values are used to make criteria for low, medium and high-intensity upwelling. Based on predetermined upwelling criteria, it is used to delineate upwelling areas, so that areas of weak, medium and strong upwelling can be mapped and calculate the upwelling area every month.

2.2.1. Method of Collecting Data Sea Surface Temperature and chlorophyll-a data in this study use daily data Level 3 of Aqua MODIS (Moderate Resolution Imaging Spectroradiometer) satellite image with a 4 km image resolution. Data in the form of NET Common Data File (NetCDF) for a period of 10 years from the 1st January 2008 to December 31, 2017, downloaded from the website https://oceancolor.gsfc.nasa.gov/cgi/13. Wind data in this study was obtained from the Advanced SCATterometer (ASCAT) in the form of daily average data with a spatial resolution of 0.125 x 0.125 in the NET Common Data File (NetCDF) format. The period wind data as long as 10 years from 2008 to 2017. This data downloaded from the website https://manati.star.nesdis.noaa- .gov/datasets/ASCATData.php. Wind data used consists of the zone wind longitudinal component (u) in the East-West direction and meridional (v) in the North-South direction, in the form of velocity data in units of knots and direction data in units of degrees.

2.2.2. Processing Data and Analysis Processing SST and chlorophyll-a data using SeaDAS 7.0 software. Wind data is processed with ODV (Ocean Data View) software. Data processing produces data in the form of txt, then processed with mapping software. Data processing also uses excel software to produce graphics and calculate the standard deviation. Data analysis is performed statistically and visually based on processed data in the form of maps and graphics.

http://iaeme.com/Home/journal/IJCIET 744 [email protected] Variability of Upwelling in Bone Bay and Flores Sea

3. RESULTS AND DISCUSSION

3.1. Sea Surface Temperature and Chlorophyll-a Variations Sea surface temperature (SST), chlorophyll-a and winds monthly climatology variations on 2008-2017 in upwelling areas showed in Figure 2.

Figure 2 Monthly Variations in SST, Chlorophyll-a and Wind Climatology from 2008-2017. The three parameters in Figure 2 show interrelated patterns. Sea Surface Temperature variability showed inversely proportional to the wind and chlorophyll-a parameters when the wind strengthened SST decreased and chlorophyll-a increased. Sea surface temperatures in the waters of Bone Bay and the Flores Sea show the lowest values in the east season, namely August and high-value SST occur twice, namely in the Transition Season 1 (April) and Transition Season 2 (November). The very low decline in SST that occurred in the eastern season, seemed very related to the increase in wind speed. The highest wind speed peak occurred in August which reached 6.5 m / s. The general increase of the wind speed in the sea will lead to a cooling water SST process [3,4,5,6]. The occurrence of cooling can be because the mixing process can also be due to the occurrence of an upwelling process [7]. The value of SST which dropped dramatically in the East Season which reached its lowest point in August with a value of 27oC in the climatological average (Figure 2) and on a transect in August showed the lowest SST value of 26.8 oC (Figure 3A), indicated that because of the upwelling process. Indications of the upwelling process can be seen from the latitudinal and longitudinal transects of the SST and chlorophyll-a distribution values in August in the Flores Sea in the Southwest of Buton Island. Based on the transect, the SST value is lower than the surrounding area and the chlorophyll-a value is higher than the surrounding area, which is centered on longitude between 122.35-122.81oE and latitude between 5.72 to 6.14 oS (Figure 3A and 3B). Areas with lower SST than surrounding and higher chlorophyll-a is an indicator of upwelling [8,9,10].

http://iaeme.com/Home/journal/IJCIET 745 [email protected] Kunarso, Raymundus Putra Situmorang, Sri Yulina Wulandari and Aris Ismanto

(A)

3 27.6 ) 3 2.5 27.4

2 27.2

C) o

1.5 27

a a (mg/m -

1 26.8 SST( 0.5 26.6

0 26.4 Chlorophyll

Longitude (oE)

Chlorophyll-a SST

(B)

1.5 27.8

) 3 27.6

1 C)

27.4 o a a (mg/m - 27.2

0.5 SST( 27 0 26.8

-5.72-5.77-5.81-5.85-5.89-5.93-5.97-6.02-6.06 -6.1 -6.14-6.18 Chlorophyll Latitude (oS)

Chlorophyll-a SST

Figure 3 Latitudinal Transect (A) and Longitudinal Transect (B) Chlorophyll-a and Sea Surface Temperature August 2008-2017 in Bone Bay and the Flores Sea. The increased chlorophyll-a value in the East Season - Transition Season 2 (June- October) with a concentration range of 0.3-2.6 mg / m3, with a peak occurring in August, appears to be related to the occurrence of upwelling in Bone Bay and the Flores Sea. The upwelling process removes the water mass from the inner layer which has a higher nutrient concentration than the surface. Increasing the concentration of nutrients in the surface layer supported by sufficient sunlight intensity will improve the photosynthetic process of phytoplankton, which triggers increased growth and proliferation. Increased growth and proliferation of phytoplankton resulted in an increase in phytoplankton concentrations that were evident from the indicators of high chlorophyll-a concentration, this is in accordance with that to be explained by Setiawan and Kawamura [11], Wirasatriya et al [4].

3.2. Intensity and Area of Upwelling Determination of the criteria classification range value of upwelling intensity is based on the range of the average value of sea surface temperature and chlorophyll-a at the location of the occurrence of upwelling phenomena, namely in the waters of Bone Bay and the Flores Sea. The classification value of upwelling intensity is divided into three criteria shown in Table 1 with indicators of sea surface temperature and chlorophyll-a. Criteria for the intensity of upwelling include the Strong Upwelling Intensity (SU) with the classification of SU sea

http://iaeme.com/Home/journal/IJCIET 746 [email protected] Variability of Upwelling in Bone Bay and Flores Sea surface temperature values ≤ 27.71oC and SU chlorophyll-a value classification ≥ 0.785 mg/m3. Medium Upwelling Intensity (MU) with classification of sea surface temperature values 27.71oC ≤ MU < 27.97oC and classification of chlorophyll-a value 0.555 mg/m3 m MU < 0.785 mg/m3. Weak Upwelling intensity (WU) with a classification of sea surface temperature values of 27.97oC ≤ WU < 28.51 oC and classification of chlorophyll-a value of 0.493 mg/m3 ≤ WU <0.555 mg/m3.

Table 1 Criteria for Upwelling Intensity SST (oC) Chlorophyll-a (mg/m3) Upwelling Criteria 27,97 ≤ WU < 28,51 0,493 ≤WU < 0,555 Weak Upwelling Intensity 27,71 ≤ MU < 27,97 0,555 ≤ MU< 0,785 Medium Upwelling Intensity SU ≤ 27,71 SU ≥ 0,785 Strong Upwelling Intensity Based on that upwelling criteria, the locations of upwelling in Bone Bay and the Flores Sea only occurs during certain months, from June to September (Table 2) with different intensities of each month.

Table 2 Upwelling variability based on the value of Sea Surface Temperature and Chlorophyll-a in Bone Bay and the Flores Sea

Variability of upwelling based on the value of sea surface temperature and chlorophyll-a is shown in Table 2. Weak upwelling occurs in June and September with a mean sea surface temperature of 28.51 oC; 27.95 oC and concentration of chlorophyll-a value of 0.4931 mg/m3; 0.5582 mg/m3. Furthermore, Upwelling with Medium Intensity occurred in July with a mean value of sea surface temperature of 27.64 oC and a concentration of chlorophyll-a value of 0.6464 mg/m3. Whereas upwelling with Strong Intensity occurred in August and on that month was the peak of upwelling with sea surface temperature of 27.27 oC and the concentration of chlorophyll-a value of 1.0076 mg/m3. Base on Table 2 shows that the upwelling phenomenon began in June and ended in September. This can happen, apparently related to the decrease in the intensity of upwelling. This upwelling temporal variability is influenced by the East Season wind which shifts to the West Season, where this process is associated with a shift in the center of low air pressure over the Australian continent which causes the speed of East Season winds to decline along with the change of moon [12,13]. Wind is the main driver in the occurrence of upwelling phenomenon in the Bone Bay and the Flores Sea, so variability temporal of wind speed and direction will effect to the upwelling temporal variability. This statement is in accordance with the results of research from Kunarso et al., [8].

http://iaeme.com/Home/journal/IJCIET 747 [email protected] Kunarso, Raymundus Putra Situmorang, Sri Yulina Wulandari and Aris Ismanto

a) b) a) b)

c) d) c) d)

Figure 4 Upwelling intensity map in a) June, b) July, c) August, d) September Based on the upwelling intensity use SST and chlorophyll-a indicators (Table 2), the spatial distribution of upwelling can be made, as shown in Figure 4. Based on the figure, it appears that weak upwelling emerged from June from the Southwest of Wakatobi Islands and the Waters of South Sulawesi Beach. In July Upwelling expanded more widely in the Southwest of Wakatobi Islands, Southwest of Buton and Muna Islands, and South Coast of South Sulawesi (Figure 4b). The peak of the widest upwelling area occurred in August with the center of strong upwelling occurring in the Southwest of Buton Island (Figure 4c). The medium to strong intensity upwelling range of up to 1473.08-3907.59 km2 (Figure 5). The extent of upwelling of weakness ranges from 54.59 to 672.39 km2 (Figure 4a and 4d). The widest upwelling distribution that occurred in August reached 3097.59 km3. Upwelling intensity is related to the upwelling area, the intensity of strong upwelling is characterized by a large upwelling area, conversely, the intensity of weak upwelling is a narrow area. The upwelling that occurred in the Flores Sea south of Southeast Sulawesi Province, was apparently due to the existence of Ekman Transport generated by winds that blew west and northwest which tended to be parallel to the coastline in the South Coast of Southeast Sulawesi Province (Figure 6c). Winds along this coastline cause Ekman transport to the southwest. The vacuum of water mass that occurs in the Southwest of Buton and Southwestern Islands of Wakatobi Islands is filled by a cooler mass of water from the lower

http://iaeme.com/Home/journal/IJCIET 748 [email protected] Variability of Upwelling in Bone Bay and Flores Sea layers, so there is an upwelling process. This process is in accordance with what was explained by Kunarso et al., [8] Setiawan and Kawamura [11]. The pattern of the upwelling spread in August leads to the Southwest as far as 163.52 km, this follows the pattern of the East Season's wind movement that is moving towards the West.

Figure 5 Area of Upwelling Area from June to September The phenomenon of upwelling in the southern part of Bone Bay only occurs around June, July, August, and September. This phenomenon occurs every year in the same month. From this phenomenon, upwelling in the southern location of Bone Bay can be classified as periodic upwelling. This is also supported by Kunarso et al., [8] that upwelling in the southern Gulf of Bone occurs in June, July, August, and September. The pattern of wind movement, wind speed also influences the driving and pattern of spreading upwelling in Bone Bay and the Flores Sea. The important factor is the direction of the wind to be parallel to the coastline in the South Coast of Southeast Sulawesi Province, this wind characteristic occurs on June, July, August, and September (Figure 6).

a) b)

c) d)

Figure 6 Wind Speed and Direction in Bone Bay and Flores Sea (a) June, (b) July, (c) August, (d) September

http://iaeme.com/Home/journal/IJCIET 749 [email protected] Kunarso, Raymundus Putra Situmorang, Sri Yulina Wulandari and Aris Ismanto

4. CONCLUSION Temporal patterns of upwelling spread in the waters of Bone Bay and the Flores Sea occur from June to September and the peak occurs in August. Based on upwelling intensity categories in June and September are weak upwelling, July is moderate upwelling and August includes strong upwelling. Spatially spreading patterns indicate dominant upwelling occurs in South Buton Island and west of Wakatobi Islands. Upwelling develops to the southwest of Buton Island as far as 163.52 km. The estimated upwelling area in June was around 54.59 km2, developing to the peak in August of 3907.59 km2 and in September it was reduced to 672.39 km2.

ACKNOWLEDGMENTS We thank Dien of Fisheries and Marine Science Faculty: Prof. Dr. Ir. Agus Sabdono, M.Sc, and Head of Oceanography Departement for supporting this research administrative.

REFERENCES

[1] Pranowo. W.S., Puspita. C.D., Bramawanto. R., Adi. R.A., dan Kusumawardani. A.R.T.D. 2014. The Current Dynamic in Support Marine Aquaculture in Bone Bay. Journal Harpodon Borneo, Edition December 2014. [2] Illahude A. G. 1978. On The Effecting The Productivity of The Southern Makassar Strait. Marine Research in Indonesia. 21: 81-107 [3] Setiawan, R.Y., and Habibi, A. 2011. Satellite Detection of Summer Chlorophyll-a Bloomin the Gulf of Tomini. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 4, No. 4. [4] Wirasatriya, A., Setiawan, R.Y., Soebardjo, P. 2017. The Effect of ENSO on the Variability of Chlorophyll-a and Sea Surface Temperature in the Maluku Sea. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 10, No. 12. [5] Wirasatriya, A, Kunarso, Maslukah, L, Satriadi, A, Armanto, R D. 2018a. Different responses of chlorophyll-a concentration and SeaSurface Temperature (SST) on the southeasterly wind blowing in the Sunda Strait. IOP Conf. Series: Earth and Environmental Science 139 (2018) 012028. [6] Wirasatriya, A., Prasetyawan, I.B, Triyono, C.D., Muslim, Maslukah, L., 2018b. Effect Of ENSO On The Variability Of SST And Chlorophyll-A In Java Sea. 3rd International Conference On Tropical And Coastal Region Eco-Development 2017, IOP Conference Series: Earth and Environmental Science 116 (2018) 012063 [7] Kunarso, Zainuri, M., Ario, R., Munandar, B. Prayogi, H. 2018. Impact of Monsoon to Aquatic Productivity and Fish Landing at Pesawaran Regency Waters. IOP Conf. Series: Earth and Environmental Science 116 (2018) 012021. [8] Kunarso., Supangat. A., Ningsih. N.S., and Hadi. A. 2009. Upwelling and Tuna Fishing Ground in Nusantara Sea. Diponegoro University Press, Semarang, pp 211. [9] Villanoy, C.L., O.C. Cabrera, A. Yñiguez, M. Camoying, A. de Guzman, L.T. David, and P. Flament. 2011. Monsoon-driven coastal upwelling off the Zamboanga Peninsula, Philippines. In Oceanography 24 (1): pp 156–165, doi:10.5670/oceanog.2011.12. [10] Atmadipoera, A.S., Khairunnisa, Z, Kusuma, D.W. 2018. Upwelling characteristics during El Nino 2015 in Maluku Sea. IOP Conf. Series: Earth and Environmental Science 176 (2018) 012018.

http://iaeme.com/Home/journal/IJCIET 750 [email protected] Variability of Upwelling in Bone Bay and Flores Sea

[11] Setiawan, R.Y and Kawamura, H., 2011. Summertime Phytoplankton Bloom in the South Sulawesi Sea. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 4, No. 1. [12] Susanto. R. D., Gordon. A. L., dan Zeng. Q. 2001. Upwelling Along the Coasts of Java and Sumatera and its Relation to ENSO. Geophysical Research Letters. 28 (8): 1599 – 1602 [13] Susanto.R.D., Moore, T.S., dan Marra. J. 2006. Ocean Color Variability in Indonesian Seas during the SeaWiFS Era. Journal Geochemistry Geophysics Geosystems, 7: 1525 – 2027.

http://iaeme.com/Home/journal/IJCIET 751 [email protected]