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226 METEOROLOGY FOR MARIAERS

Chin a Seas and other Regions Westwards of the Main Circulation

In the China Seas and Java Sea the currents are monsoonal. During the south-west monsoon the generał direction of currcnt is wcstcrly in the Java Sea and north-eastcrly in the China and Eastern Seas. In the Yellow Sca the currents are complcx and variable. During the north-east monsoon the currents become mainly southerly in the Yellow Sca, south-wcsterly in the Eastern and China Seas and casterly in the Java Sea. In the Southern part of the China Sea there is a variable currcnt area west of Borneo and Palawan in both monsoons, but a weak monsoonal current runs along the west coasts of these islands, altcrnating between north-eastcrly and south-westerly during the year. The eastern part of the Eastern Sca is occupicd by the Kuro Shio.

In the China Seas, the north-eastcrly currcnt is found from May to August inclusive. Scptembcr is the transitional month, but the north-easterly currcnt still persists in the Southern part. In October the south-westerly current becomes established evcrywhere, and this continucs till about the middle of March. April is the transitional month, but the south-westerly currcnt still persists in the Southern part.

In the Java Sca the wcsterly currcnt runs from Junc to Septcmber and the easterly currcnt from Xovembcr to March. April, May and Octobcr are transitional months.

In the Japan Sca the circulation is countcr-clockwisc all the year, the north-going current on the cast side of the sea, known as the Tsushima Shio, is a branch of the Kuro Shio which has passed through Korca Strait. Part of the Tsushima Shio branchcs ofT through Tsugaru Kaikyó and flows into the Oya Shio, and another part branchcs off through Sóya Kaikyó. The south-going currcnt on the west side of the sca, past Vladivostok, is called the Liman Current.

In the central parts of the Sca of Okhotsk the currents are variablc. Nearer the coasts there is a counter-clockwise circulation, but along the west coast of Kamchatka the llow is southerly elose inshore. OfT the coast of Sakhalin Island the south-going currcnt is known as the East Sakhalin Current.

SOUTH PACIFIC OCEAN

Main Circulation

The main circulation is counter-clockwise. Less is known about the South Pacific currents than thosc of the other oceans south of the cquator, because of its great size and on account of the large arcas, particularly in the cast, which are not frecjuentcd by shipping.

The South Equatorial Current of the Pacific, though lying mainly south of the cquator, extends to about latitude 5°n though varying according to longitude and season. Its northern limit is defined by the cast-going Equatorial Countcr-currcnt of the North Pacific, immcdiately north of it.

South of about latitude G°s the strength of the currcnt gradually dccreascs southwards whilc the direction becomes morc south-westerly. Somc westerly component persists at least to latitude 20°s. Between about longitudcs QO°w and I35°w there is a weak southerly flow between latitudes 20°s and 30°s.

On the west side of the ocean the coursc of the South Equatorial Current varics scasonally. In June to August the whole current follows the north coast 227

CURRENT CIRCULA TIONS OF THE OCE ANS

of New Guinca to the north-wcstwards and thcn rccurvcs north and north-castwards, entcring the east-going Equatorial Counter-current of the North Pacific. In Dcccmbcr to Fcbruary the South Equatorial Current docs not pass into the counter-current; it recurves south-wcstwards and southwards and flows past the north coast of New Guinca in a south-castcrly direction. There is thus a complete reversal of current along this coast during the year.

The west side of the main circulation is not wcll marked, cxcept along the Australian coast from Great Sandy Island to Capc Howe, where the East Australian Coast Current sets southwards.

In the region of the Great Barricr Rccf the flow is south-easterly in the northern winter but in the northern summer, north of about latitude i8°s, the flow is north-westerly and continues westwards through the Torres Strait.

The south side of the main circulation is formed by the Southern Ocean Current which sets to the east or north-east. Observations are scanty ovcr most of this region.

Between Australia and New Zcaland easterly sets prcdominatc. The bulk of the East Australian Coast Current mixes with the water of the Southern Ocean Current and flows eastwards towards New Zcaland. The current sets north-eastwards along both the west and cast coasts of South Island, New Zcaland.

The bulk of the Southern Ocean Current enters the South Atlantic south of Cabo dc I lornos. The northern part of this currcnt, however, mccts the coast of Chile between Isla de Chiloe and the Golfo de Penas, where it divides; part goes northwards to form the beginning of the Peru Current and part follows the coast south-eastwards to rejoin the Southern Ocean Current south of Cabo dc Hornos.

The cast side of the circulation is formed by the relatively cool Peru Current, formcrly known as the Humbolt Current. It follows the coastlinc northwards to somewhcrc ncar the cquator. Between the Golfo de Guayaąuil and the equator the bulk of the Peru Currcnt trends seawards and passes into the South Equatorial Current. The Peru Current has a width of perhaps 300 nautical miles or morc.

A branch of the Peru Currcnt continues northwards up the coast during most of the year and enters the Gulf of Panama.

During the northern winter in the eastern North Pacific, the east-going Equatorial Counter-current cxtcnds further south than at other seasons. A branch of this currcnt thcn turns southwards along the coast of Ecuador into the South Pacific, but in most ycars its Southern limit is only a few degrees south of the equator. This is callcd El Nino, or the Holy Ciiild Current, as in some ycars it begins to flow about Christmas-timc, although it is morę regularly observed in Fcbruary and March. In exccptional ycars it cxtcnds down the coast of Peru, occasionally to bcyond Callao, when the intrusion of this warm water into a region normally occupied by the cool Peru Current kills fish and other marinę lifc.

Central Oceanie Region

Between about latitudcs 20°s and 40°s, and longitudes 90°w and 180° there is a vast area where observations are scanty and where, as far as is known, the currents are mainly light and variable. The centre of the generał counter-clockwise circulation of the South Pacific lics somewhcrc in this region and there may wcll bc scvcral eddies with ccntres locatcd not far from latitude 30°s.