The Australia–Indonesia borderSee map by the Geoscience Australia is a maritime boundary running west from the two countries' tripoint maritime boundary with Papua New Guinea in the western entrance to the Torres Straits, through the Arafura Sea and Timor Sea, and terminating in the Indian Ocean. The boundary is, however, broken by the Timor Gap, where Australian and East Timorese territorial waters meet and where the two countries have overlapping claims to the seabed.
Australia and Indonesia also share a common maritime border in the Indian Ocean between Australia's overseas territory of Christmas Island and the Indonesian island of Java.
A characteristic of the maritime border between the two countries is the separation of the ownership of the seabed (essentially the continental shelf) and ownership of the water column (exclusive economic zone), each with its own boundary. Ownership of the seabed gives the country rights over all mineral resources in the seabed while ownership of the water column allows a country fishing rights and rights to other resources of the water in the specified area. The 1997 treaty establishing this and the western parts of the border, as well as that between Christmas Island and Java, has however not been ratified and is not in force. This was because the independence of East Timor required amendments to the 1997 treaty and agreement over them by the two parties is still pending.
The Border The boundary is separated into three segments, with the first two broken by the Timor Gap. The first is between the Australia – Indonesia – Papua New Guinea tripoint at , and the point whether the territorial waters of the two countries touch the eastern limits of the territorial waters claimed by East Timor at . The second segment runs westward from the point where the territorial waters of the two countries touch the western limits of East Timor's territorial waters claim at , to in the Indian Ocean. The third is between the Australian external territory of Christmas Island and the Indonesia island of Java, in the Indian Ocean.
The boundary is established by four treaties, the fourth of which has been signed but not yet ratified. The Agreement between the Government of the Commonwealth of Australia and the Government of the Republic of Indonesia establishing Certain Seabed Boundaries signed in Canberra on 18 May 1971 established part of the eastern segment of the seabed boundary (as well as Indonesia's maritime boundary with Papua New Guinea in the Torres Straits) while the Agreement between the Government of the Commonwealth of Australia and the Government of the Republic of Indonesia establishing certain seabed boundaries in the area of the Timor and Arafura Seas, Supplementary to the Agreement of 18 May 1971 which was signed in Jakarta on 9 October 1972 demarcated the rest of the eastern segment and a portion of the western segment of the seabed boundary. A third agreement, Agreement between Australia and Indonesia concerning Certain Boundaries between Papua New Guinea and Indonesia established the demarcation between the soon to be independent Papua New Guinea and Indonesia was signed in Jakarta on 12 February 1973. A fourth treaty, the Treaty between the Government of Australia and the Government of the Republic of Indonesia establishing an Exclusive Economic Zone Boundary and Certain Seabed Boundaries (informally known as the Australia–Indonesia Maritime Delimitation Treaty) which was signed in Perth on 14 March 1997 (however not ratified), proposes to extended the western segment of the seabed boundary to its termination point in the Indian Ocean.
The basis for establishing the boundary in the 1971 and 1972 treaties was that of the "natural prolongation" of the physical continental shelf. This resulted in the boundary running significantly north of the median line between the shores of Australia and Indonesia, thus benefiting Australia in terms of the division of the seabed ownership. The International Law view of settling overlapping claims has since then moved towards the median-line concept, although Australia still holds the view that natural prolongation was still relevant to determine the sovereignty of the seabed. This resulted in the separate treatment of establishing the seabed boundary and that for the water column, or essentially, the separation of the continental shelf and exclusive economic zone boundaries under the 1997 treaty.
The independence of East Timor on 20 May 2002 may result in changes in the Australia–Indonesia border near the Timor Gap which were established by the three treaties. Provisions of the 1997 treaty on matters concerning the Timor Gap – such as reaffirming the Timor Gap Treaty between Australia and Indonesia and the drawing of the water column boundary through the area of joint development – would no longer be applicable with East Timor becoming the rightful claimant of the seabed and exclusive economic zone in the area. Furthermore, the "Timor Gap terminal points" established by the 1972 treaty, namely Points A16 and A17, might have to be renegotiated by Australia, East Timor and Indonesia, as East Timor might have the basis to seek a "wider" Timor Gap than originally provided by Australia and Indonesia.V. Lowe, C. Carleton & C. Ward, "In the Matter of East Timor's Maritime Boundaries", opinion prepared for Petrotimor Companhia de Petroleos, S.A.R.L., 11 April 2002 available at Petrotimor's website
Seabed (continental shelf) boundary
Eastern segment The eastern segment of the boundary was established by both the 1971 and 1972 treaties, the former delimiting the border from A3 to A12 and the latter extending it from A12 to A16, which lies on the eastern border of the Australia – East Timor joint petroleum development area. Points A1, A2 and A3 form part of the Indonesia – Papua New Guinea border which was also established under the 1971 treaty when Papua New Guinea was still an Australian territory.
Point Longitude (E) Latitude (S) Remarks Australia, Indonesia and Papua New Guinea common tripoint A3 139° 12' 10° 50' Eastern segment of the Australia-Indonesia seabed boundary A4 138° 38' 10° 24' A5 138° 35' 10° 22' A6 138° 13' 10° 9' A7 137° 45' 9° 57' A8 135° 29' 9° 8' A9 135° 13' 9° 17' A10 135° 3' 9° 22' A11 134° 50' 9° 25' A12 133° 23' 8° 53' A13 133° 14' 8° 54' A14 130° 10' 9° 25' A15 128° 9° 25' A16 127° 56' 9° 28' This point lies on the eastern border of the Australia-East Timor joint petroleum development area, may be subject to change after negotiations with East Timor
Western segment The 1972 treaty brought the boundary to Point A25 to the north-east of Australia's Ashmore Island. The 1997 treaty extended it further west, terminating at A82 in the Indian Ocean where Australia's and Indonesia's exclusive economic zone limits diverge.
Point Longitude (E) Latitude (S) Remarks Western segment of the Australia-Indonesia seabed boundary pursuant to 1972 treaty A17 126° 10° 28' This point lies on the western border of the Australia-East Timor joint petroleum development area, may be subject to change after negotiations with East Timor A18 125° 41' 10° 37' A19 125° 19' 11° 1' A20 124° 34' 11° 7' A21 124° 10' 11° 25' A22 124° 11° 26' A23 123° 40' 11° 28' A24 123° 26' 11° 23' A25 123° 14' 11° 35' Western extension of the boundary pursuant to 1997 treaty A26 123° 14' 4.5" 11° 48' 6.1" A27 123° 13' 38.1" 11° 47' 59.3" A28 123° 12' 12.7" 11° 47' 40.3" A29 123° 12' 5.1" 11° 47' 38.9" A30 123° 11' 2.9" 11° 47' 25.6" A31 123° 5' 27.9" 11° 46' 25.7" A32 123° 0' 49.7" 11° 46' 31.8" A33 122° 59' 22.9" 11° 46' 44.2" A34 122° 57' 32.5" 11° 47' 07.4" A35 122° 56' 8.2" 11° 47' 31" A36 122° 53' 24.7" 11° 48' 32.1" A37 122° 50' 34.5" 11° 50' 0.6" A38 122° 49' 19.9" 11° 50' 48.1" A39 122° 48' 5.1" 11° 51' 12.9" A40 122° 47' 38.9" 11° 51' 22.4" A41 122° 46' 21.2" 11° 51' 53.3" A42 122° 44' 16.8" 11° 52' 53.4" A43 122° 41' 4.3" 11° 54' 56.3" A44 122° 40' 0.5" 11° 55' 46.7" A45 122° 35' 27.9" 12° 0' 41.4" A46 122° 34' 33.8" 12° 2' 5" A47 122° 33' 55.8" 12° 3' 12.2" A48 122° 32' 24.1" 12° 6' 44.6" The border then proceeds southerly in an arc of a circle drawn concave to Ashmore Island with a radius of to Point A49 A49 122° 31' 6.6" 12° 14' 25.8" A50 120° 0' 46.9" 13° 56' 31.7" A51 120° 0' 46.9" 12° 46' 27.9" A52 119° 59' 31" 12° 45' 47" A53 119° 59' 15" 12° 45' 38" A54 119° 56' 13" 12° 43' 46" A55 119° 53' 18" 12° 41' 57" A56 119° 52' 57" 12° 41' 46" A57 119° 52' 38" 12° 41' 36" A58 119° 50' 28" 12° 40' 33" A59 119° 40' 33" 12° 35' 43" A60 119° 33' 16" 12° 32' 31" A61 12° 29' 19" 119° 27' 17" A62 12° 25' 43" 119° 21' 35" A63 12° 24' 59" 119° 20' 34" A64 12° 23' 58" 119° 16' 35" A65 12° 23' 42" 119° 15' 23" A66 12° 21' 51" 119° 9' 3" A67 12° 20' 21" 119° 5' 0" A68 12° 19' 55" 119° 2' 40" A69 12° 18' 50" 118° 58' 31" A70 12° 17' 54" 118° 55' 12" A71 12° 15' 57" 118° 49' 30" A72 12° 13' 12" 118° 43' 9" A73 12° 11' 1" 118° 39' 0" A74 12° 10' 26" 118° 37' 28" A75 12° 10' 6" 118° 35' 16" A76 12° 7' 46" 118° 25' 07" A77 12° 6' 21" 118° 20' 45" A78 12° 4' 19" 118° 7' 44" A79 12° 4' 8.8" 118° 6' 14.4" A80 12° 4' 24.9" 118° 6' 17.2" A81 12° 49' 54.8" 118° 14' 22.6" A82 13° 5' 27.0" 118° 10' 8.9"
Christmas Island/Java segment Christmas Island is an external territory of Australia located in the Indian Ocean south of the southern coast of Java. The maritime boundary between the island and Indonesia which was established by the 1997 treaty is a modified median line which lies closer to the island by virtue of it being an isolated island lying next to the coastline of a larger country. The boundary generally runs east–west and terminates both ends where the boundary of the Australian exclusive economic zone created around Christmas Island diverges from the Indonesian EEZ. Unlike the boundary in the Arafura and Timor Seas, there are no separate boundaries for the seabed and water column.
Point Longitude (E) Latitude (S) Christmas Island/Java boundary C1 109° 1' 25.8" 11° 10' 24.6" C2 105° 50' 55.4" 9° 46' 49.8" C3 102° 34' 12.7" 8° 52' 14.1"
Water column (exclusive economic zone) boundary A separate "water column boundary", essentially an exclusive economic zone boundary for the ownership of fishery resources, was created under the 1997 treaty. The boundary starts from the Australia-Indonesia-Papua New Guinea tripoint at , which is Point A3 of the seabed boundary and designated as Point Z1 of the water column boundary. It runs to the south of the Australia-Indonesia seabed boundary and terminates in the Indian Ocean where the Australian and Indonesia EEZ diverge. The boundary essentially follows the Provisional Fisheries Surveillance and Enforcement Line (PFSEL), a non-treaty status agreement made in 1981 between the two countries, and is generally based on the median line principle measures from the Australian mainland and Indonesian archipelagic baseline.
The 1997 treaty essentially separates the sovereignty of the seabed and water column in the area between the water column boundary and the seabed boundary, whereby Australia has sovereignty over the seabed and its resources, while Indonesia has sovereignty over the water column and the resources which live in it.