INFLUENCE OF UPWELLING IN THE SOUTHERN WATERS OF JAVA ON CO2 CONCENTRATION IN KOTOTABANG, AGAM DISTRICT WEST

Absorption of atmospheric CO2 by the sea through two processes, namely solubility pumps and biological pumps. This study aims to determine the effect of upwelling in the southern waters of Java on atmospheric CO2 concentrations in Kototabang. The data used are in situ CO2 concentration, sea surface temperature and chlorophyll-a concentration from 2004-2016. The method used was descriptive analysis. The results showed that upwelling that occurred during JJA-SON caused a decrease in sea surface temperature to 26.8 °C and 27.1 °C respectively, as well as an increase chlorophyll-a concentration to 2.03 mg/m3 and 2.19 mg/m3. In both seasons CO2 concentration in Kototabang dropped to 385.8 ppm and 385.4 ppm. Meanwhile, when there was no upwelling during DJF-MAM, sea surface temperatures rose to 28.8 °C and 29.0 °C, and chlorophyll-a concentration dropped to 0.32 mg/m3 and 0.54 mg/m3. CO2 concentration in DJF and MAM increased to 386.3 ppm and 386.5 ppm. Based on these results it is known that when upwelling occurs, CO2 concentration decrease and vice versa.


INTRODUCTION
CO2 is one of the greenhouse gases that received much attention. The sea and biosphere are the main absorbents of CO2 in the atmosphere. The global ocean is estimated to have absorbed about 30% of the concentration of CO2 in the atmosphere over the past few decades [1]. Absorption of atmospheric CO2 by the sea through two processes called solubility pumps and biological pumps [2]. In a solubility pumps, atmospheric CO2 enters the ocean through the process of gases exchange between air and sea which is affected by sea temperature and wind speed.
Biological pumps has an important role in the transfer of CO2 from the atmosphere to the interior of the ocean and sediments [3].
The transfer process of CO2 is determined by the amount of primary productivity [4].
Primary productivity takes CO2 through photosynthesis. The content of primary productivity is indicated by the concentration of chlorophyll-a [5]. And meanwhile, solubility pumps is affected by sea temperature. If the sea temperature gets colder, the more CO2 is absorbed by the sea. The concentration of chlorophyll-a in the marine waters is influenced by upwelling.
Upwelling location has a high chlorophyll-a concentration [6,7]. Upwelling is a rise of water mass from below to the surface layer.
This mass of water has cold temperature, high salinity and nutrients. Therefore, the presence of chlorophyll-a concentration determines the biological pumps. Chlorophyll-a has an important role in the biogeochemical cycle in the ocean [8] and affect the temperature and circulation of surface currents [9].
Upwelling in the southern waters of Java is known very intensive [10,11]. This upwelling location reaches the west coast of Sumatra. Research about upwelling in the south of Java has been carried out, among others by [12,13,14,15]. The intensity of upwelling gets stronger when occur El Niño, on the contrary it gets weaker when occur La Nina [16,17,18].
There has not been much research on the effect of upwelling on atmospheric CO2 concentration. So far, the focus of research has only been on the impact of upwelling on the marine environment such as changes in sea surface temperature, chlorophyll-a concentration, salinity and its relation to fish catch production. Whereas upwelling has a big impact on weather and climate variability [19,20]. Therefore, research on the effect of upwelling on CO2 concentrations needs to be done in order to understand the carbon cycle between the atmosphere and the ocean. The purpose of this study was to determine the effect of upwelling in the southern waters of Java on concentration of CO2 in Kototabang.

Research location
The study location included the southern waters of Java from the coastline to 9 ° S and Kototabang, Agam Regency, West Sumatra located at coordinates 0 ° 12'07 '' LS and 100 ° 19 '05 '' BT as shown in Figure 1.

Data
The data used consists of chlorophylla concentration, sea surface temperature,

Analysis
The         . This is due to low sea surface temperature so that the partial pressure of CO2 at sea level is lower than in the atmosphere.
The solubility and absorption of CO2 is determined by sea temperature condition and the amount of primary productivity. CO2 solubility in the sea will be faster with a decrease in sea surface temperature, on the contrary ocean warming slows the solubility of CO2 [26,27]. Increasing of primary productivity will reduce pCO2 of surface water and  DAN PENDIDIKAN KIMIA), Vol. 5, No. 1, 2020, pp. 8-15 13 CO2 flux between the air-sea become negative, so that the sea acts as an absorber of CO2 [28]. The higher primary productivity, the greater the ability of the ocean to absorb CO2. The same condition was shown that in the Kodek Bay acts as an absorber of atmospheric CO2 because it has a high chlorophylla concentration [29].