THERMAL FRONT ANALYSIS IN THE EAST INDONESIAN SEAS YEAR 2006-2020

• Main Author: Aulia Lukman, Annisa
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/70776
• Institution: Institut Teknologi Bandung

The physical parameter of the ocean that has various purposes in knowing ocean phenomena is sea water temperature. Analysis of sea temperature contributes to the investigation of ocean phenomena, one of which is the thermal front. Research on the spatial distribution of thermal fronts in Indonesian waters has been widely studied. However, studies that examine the mechanism of thermal front formation and link the thermal fronts to upwelling and eddy currents have not been studied comprehensively. This research aims to determine the characteristics and mechanism of thermal front formation in eastern Indonesian seas, as well as to analyze the effect of upwelling and eddy currents on the formed thermal front. The data used in this study are SST and chlorophyll-a data from AquaMODIS satellite imagery, 443 nm RRS data, 555 nm RRS data and surface currents from Marine Copernicus, and SLA data from the Climate Data Store Catalog. The period of use of each data is 15 years (2006-2020), except for SLA data, which is 11 years (2010-2020). This research method is SPL satellite imagery data processing, thermal front detection with the SIED method, and Rrs 443 nm and Rrs 555 nm spatial and temporal data processing. The thermal front that has been obtained is then calculated statistically to see the monthly and monthly climatological variability. Data processing is also carried out by spatially overlaying the thermal front data with SST, and chlorophyll-a. Mathematical calculations are conducted by counting the pearson correlation coefficient of monthly thermal front data with monthly SPL, and chlorophyll-a. The upwelling region is determined based on SST, Chlorophyll-a, and SLA data, while the eddy current region is determined based on circular currents formed from surface currents shown. The results of this study indicate that the average thermal front formed from 2006 to 2020 in the eastern Indonesian Sea is 503 events or 18,711.188 pixels with a spatial resolution of 4x4 km. The maximum number of thermal fronts found in the Tolo Bay and Banda Sea areas (Fisheries Management Area of 714 or FMA 714) in August with a value of 780 events or 27,337 pixels. The minimum number of thermal fronts found in the Makassar Strait, Bone Bay, Flores Sea, and Bali Sea (FMA 713) with a value of 10,008 pixels in December, also in the Sulawesi Sea area and north of Halmahera Island (FMA 716) with a value of 282 events in May. The average length of the thermal front in the eastern Indonesian Sea is 132.448 km, with the average duration of the persistent thermal front formed during 2006-2020 is eight years. In addition, persistent thermal front formed an average of six months each year during 2006-2020. The maximum average correlation between thermal front and SST in eastern Indonesian Sea is found in FMA 715 with a value of -0.520 and the minimum in FMA 716 with a value of -0.300. Meanwhile, the average maximum positive correlation between thermal fronts and chlorophyll-a is found in FMA 715 with a value of 0.462 and a minimum in FMA 716 with a value of -0.205. Eddy currents in the eastern Indonesian seas can be found in Tolo Bay, the Banda Sea, the Sulawesi Sea, and the northern Halmahera Sea. The average percentage of thermal fronts formed in the eddy areas in these waters is 35.779%. This low percentage is suspected due to the eddy mixing process causing the thermal front dissipates faster. Meanwhile, upwelling in the eastern Indonesian seas can be found in the southern parts of the Makassar Strait, the Banda Sea, the Halmahera Sea, and the Maluku Sea. The average percentage of thermal fronts formed in the upwelling areas is 37.186%. In the upwelling area, thermal fronts can be found, despite not all thermal fronts being found in the upwelling area. It is suspected that there is a lag/lead time between the month the upwelling occurs and the month when the maximum thermal front occurs.