Transactions of the Asiatic Society of Japan/Series 1/Volume 2/Winds and Currents in the vicinity of the Japanese Islands
WINDS AND CURRENTS IN THE VICINITY
OF THE JAPANESE ISLANDS.
BY
Captain A. R. BROWN.
Japanese Government Lighthouse Service.
Read before the Asiatic Society of Japan, on
the 15th April, 1874.
———o———
While there can be no doubt of the great interest attached to the subject of this paper, it is, at the same time, one on which it is most difficult to gather a sufficient amount of information to render any remarks upon it either practically useful or sufficiently interesting to the members of this Society. The statements made in what follows have been gathered, to a great extent, from a considerable experience of the coast, and, while they may be, so far as they go, considered reliable, their incompleteness is due to the difficulties of obtaining information on the subject. This, of course, can only be properly procured by means of minute observations and records taken with instruments, and from vessels especially devoted to the purpose.
The stream known as the Japan Stream, which flows regularly along the southern Coasts of Japan, has been termed the “Gulf Stream” of the Pacific, from its supposed resemblance to the stream known by that name in the Atlantic. Indeed, the two streams are very similar in many ways. They rise in nearly the same latitude, and the course or direction in which both flow are almost identical for over 2,000 miles. The “Japan Stream” is also both warmer and salter than the surrounding waters, as is the “Gulf Stream.” But they differ from each other in as much as, while the main body of the Gulf Stream finds its way into the Arctic seas, only a small arm of the Japan Stream does so. This arm known as the Kamchatcka current flows through the Behring Straits, and it leaves the main body in about latitude 38° N., and longitude 150° E. The main current flowing in an easterly and south-easterly direction, is ultimately lost in the drift current of the Pacific. The Gulf Stream is also noted for its beautiful blue colour, while the Japan Stream is dark in colour, hence the name which has been given it of “Kuro-siwo” or Black Stream.
The Kuro-siwo, or Japan Stream, is a portion of the great equatorial current of the Pacific. The greatest strength of this current is found between the parallels of 10° and 20° of north latitude, and is believed to be occasioned by the north-east trade winds in that ocean. This current, having its source about the middle of the Pacific, flows along in a westerly direction until it nears the eastern coast of Luzon and the Bashee Islands. When it reaches this locality, its waters are, in the summer time or during the presence of the S. W. monsoon, considerably augmented from the China Sea. In winter or during the N. E. monsoon on the contrary the equatorial current is considerably drained; a portion of it Joining the drift current forced down the China Sea by the N. E. winds. This portion, when it leaves the main current, flows through the various channels between the Phillipine Islands and Formosa. It will therefore be seen that the volume and breadth of the equatorial current in this region depend, in a great measure, upon the prevailing winds in the China Sea—they being increased during S. W. winds and lessened during N. E. winds.
From Luzon the current which may now be known by the name of the Japan Stream flows northward passing between Formosa and the Meiaco-sima group, after which it turns to the north-east and strikes upon the south point of the Island of Kiusiu. In summer, as already explained, its breadth is greatly extended, and a branch of it then proceeds up the west coast of Kiusiu through the Corean straits and into the Japan Sea. From the south point of the Goto islands to Nomosaki, however, I have always found this branch to be under tidal influence. From the south of Kiusiu the main current rushes through Van Diemen Straits, and the channels between the various islands which lie to the south of them with great velocity, and, continuing its course in a north-easterly direction, it passes the east coast of Kiusiu and the south of Sikok. I have examined the logs of mail steamers for seventy voyages with the object of gaining an idea of the approximate velocity of this current under various circumstances, and I have myself made twenty voyages from which to make deductions; but I find that even with the same direction and strength of wind, and at the same season of the year, the velocity is most irregular and frequently differs to a very considerable extent. On three occasions only during these voyages its velocity exceeded 70 miles in the twenty-four hours; once in the month of January with a strong S. W. wind when it flowed 77 miles; once in June with a fresh easterly breeze 73 miles, and once in July with light variable airs 76 miles. With fine settled weather a ship steering a straight course from Satanomisaki to Irosaki may expect to average about 40 miles a day. The greatest strength will probably be found off the Boungo Channel and the south coast of Sikok. Here if the wind blows at all from the eastward a very heavy sea quickly gets up. This indeed may be expected, as while the Kuro-siwo is forcing itself to the north-east, the wind is opposing its progress, and the tides are rushing up or down the Boungo Channel at right angles to the current, and a most confused and dangerous sea is the result. This part of the coast is the dreal of Japanese seamen.
From Siwo Misaki the current continues on its course towards the chain of islands south of the Gulf of Yedo, but it has generally less velocity than off Sikok. A ship coming from Yokohama may here escape the current entirely by keeping well inshore, passing Omai-saki at a distance of from two to three miles, and then steering down towards Matoya Harbour. This route will be found of great advantage during the winter months when gales are very prevalent from W. N. W. By following it the water will be found to be much smoother, and as soon as Owari Bay is opened out the wind will hail more to the northward and will consequently be fair for shaping a course towards Oo-sima, before reaching which place it will in all probability die away entirely. I have no doubt this track will be more generally taken when the lighthouse (now in course of construction) on Omae-saki is completed, as it will occupy a shorter time and will be found less trying for both ship and passengers.
The main body of the stream now runs between the islands south of the Gulf of Yedo, a small branch, however, passes to the westward of Oo-sima (Vries) which island it rounds and flows out into the Pacific between it and Cape King. It is stated in the China Pilot that regular tides were observed about Mikomoto, (Rock Island) the flood setting W. S. W., and the ebb E. N. E., but this I think must have been an unusual occurrence, as I have visited that place some forty or fifty times, and have always found a current setting to the N. E.
Between Cape King and Inaboye-saki the Kuro-siwo is generally very strong, frequently running from two to three miles an hour. Ships bound into Yedo Bay from the northwards cannot be too careful between these two points of the coast, as during the summer months, the land is often enveloped in a dense bank of fog, and, at night time, were the proper allowance not made for the current, it might be thought that a vessel had got well round Cape Kawatsu, and the course would be altered accordingly, whereas she would be considerably short of her distance and she would probably find herself in a position of great danger somewhere to the northward of Cape King.
After passing Inaboye-saki the Japan Stream leaves the coast of Japan, but still continues to flow in a N. E. direction till its northern edge reaches about 41° N. latitude in summer. It, however, only gets as far as to 38° in winter. The main body of the stream then flows to the eastward and south-east till it nears the western shores of America, when it is deflected to the south and southwest, and ultimately joins the drift current of the Pacific. Important observations of this current have lately been made between Vancouver’s Island and San Francisco, and as it is said to be the intention of the United States Navy Department to run a line of soundings and to test the current from the former place to Japan during the coming spring, we may look for some very interesting information as to the boundaries, strength and direction of that part of the Japan Stream.
The following observations of the temperature of the Kuro-siwo were taken on board the Thabor during her various voyages:—
Between Satanomisaki
|
Between Oo-sima and
|
Straits of Tsugar.
|
42° | ||
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50° to 56° |
During the spring months narrow streaks of hot and cold water were observed to exist in the neighbourhood of Satanomashi. The cold streams were sometimes as much as eight and ten degrees lower in temperature than the rest of the stream. This peculiarity may be accounted for by the fact that a stream of cold water generally comes out of the Yellow Sea during these months and parts of it may get mixed with the warm water of the Kuro-siwo.
The branch of the Japan stream which flows through the Straits of Corea during the summer months discharges a warm current into the Japan Sea, frequently at a velocity of from two to three miles an hour. This current then runs along the west coast of Japan as far as the north of Yezo. Its breadth, however, gradually decreases and its velocity proportionately decreases till arriving at the parallel of about 38° N. latitude, after which it can scarcely be detected. When nearing the Straits of Tsugar and La Perouse, however, the current is again perceptible, and in the centre of these channels, it, at all times, sets to the eastward, its strength depending greatly upon the local winds.
On the westward side of the Japan Sea but few observations have ever been taken: a south-west set has, however, been experienced, and this, I think, may very probably be expected during the winter and early part of the spring.
It has been stated above that the Kuro-siwo flows into the Japan Sea through the Corean Straits, during summer or the continuauce of the S. W. monsoon only, but that there is a constant outset through the Straits of Tsugar and La Perouse. It is therefore evident that there must be some other cause than the current of the Japan stream to account for the eastward set through these straits during the winter months. And I think there will be little difficulty in discovering the reasons for this when we consider, that at the same time that the N. E. monsoon commences in the China Sea, and prevents the Kuro-siwo from flowing into the Corean Straits, north-west winds set in the Sea of Japan, blowing almost constantly and with considerable force. These heap (so to speak) the waters up before them until they find an outlet through the straits. The origins of both the Gulf and the Japan Streams are due to causes of a similar nature and the same results are observable on our own shores. A gale of several days’ duration from the north-west is well known to raise the whole level of the German Ocean, and then a strong current sets into the Baltic and through the Straits of Dover; and on some of the Lakes of America, during the long continuance of wind blowing in the same direction, vessels have been left nearly dry in a harbour at one end, whilst at the other the water has risen several feet above its usual level. So that I think the prevalent north-west winds on the west coast of Japan will in a great measure account for the easterly flow through the straits of Tsugar and La Perouse during winter. But, in addition to this, the fact that, in the Gulf of Tartary and North part of the Japan sea, the precipitation is very great during the winter, while the evaporation must be small, makes its clear that the result could not be other than it is.
In contra-distinction to the Japan Stream there is a cold current which comes from the North and is called the Oya-siwo. It is comparatively of small breadth and volume, but it nevertheless produces a very great effect upon the climate of the shores contiguous to it. The south of Kiusiu is washed by the strength of the Kura-siwo and in consequence has almost a tropical climate during the whole year; while the Oya-siwo runs along the East coast of Yezo, which coast is fast bound in ice for twenty miles off the land during the whole winter.
The Oya-siwo has its source in the sea of Okhotsk, one part of it is supposed to run southward along the western shores of Kamchatka and the remaining part down the east of Saghalien. Is then passes out into the Pacific through the various channels between Yezo and the Kurile Islands, and there meets that the branch of the Kuro-siwo which is called the Kamschatka Current. The result of this meeting of hot and cold streams is, that those Islands are almost constantly enveloped in fog; this is very similar to what is experienced on the Banks of Newfoundland, where the cold water from Baffin’s Bay meets the Gulf Stream.
The Oya-siwo then flows in a S. S. W. direction along the coast of Nambu towards Inaboye-saki. Between this place and the Island of King-kasan when it comes in contact with the Japan stream, it appears to be turned towards the westward, and to set in towards the shore. I found this to be particularly the case while going close along the land on one occasion. The course of the vessel had then to be continually altered towards the east so as to enable her to clear the different dangers. I am informed that in 1865 the wrecks of no fewer than six foreign built ships were to be seen on the sandy beach which lies a few miles to the north of Inaboye-saki, and it is very probable that it was this current which led to the loss of the Pacific Mail Company’s S. S. Ariel. A ship steering a course so as to pass inside a line from King-kasan to Inaboye-saki, will probably be set towards the shore and find herself much closer in than was anticipated; but on the other hand if she passes 6 or 7 miles outside the King-kasan and steers so as to pass at the same distance from Inaboye, she will then catch the Kino-siwo on her starboard bow, and will consequently be set to the eastward or away from the shore. The lead, however, is a sure guide on this part of the coast, and the temperature of the water will also invariably show which current a ship is in. The difference is sometimes as much as 20°, but it is generally not more than about 12°. In April, 1873, during a voyage from Yokohama to Hakodate, I found the temperature of the water of the Japan Stream to be 62°, and after passing Inaboye-saki the temperature dropped to 44°, the vessel being then in the Oya-siwo. On the 26th of May off the Coast of Yezo, I found the waters as low as 42°.
The winds on the Coast of Japan are very variable and it is difficult to designate any particular direction as that which is prevalent during any season. Along the southern Coast the prevailing winds throughout the year may be said to be from the north east; but during the summer months light breezes from south-east and south-west are not unfrequent. Off the Boungo Channel northerly winds often blow with great violence. With a fresh breeze from the north-east a very ugly sea quickly gets up in this locality, as has already been explained. This has probably been the cause of Satanomisaki having acquired so bad a reputation that it has been termed the “Stormy Cape.” This, in reality, however, does not appear to be the case, as the Light-keeper’s returns from that point show that very few gales occur there and that the weather is generally exceedingly fine.
Between Oo-sima and the entrance to the Gulf of Yedo, north-west winds commence about the beginning of November, and continue to blow incessantly till the latter part of March, breaking up about the time of the equinox. They generally blow with considerable force and are strongest about sunrise, moderating towards the afternoon. With these winds the weather is invariably bright and clear, so that even during night the land may be seen from a great distance; but should the direction of the wind change, and should it blow at all freshly from the eastward during this time of the year, thick and bad weather may be usually expected. It will then blow hardest from south-east and south, and will gradually draw to the westward, at the same time moderating and clearing. Gales, throughout the whole of Japan, but more especially in this part of the coast between Oosima and the Gulf of Yedo, are frequently quite local, and it is no uncommon thing to find that a heavy blow has been experienced about Rock Island, when there has been perfectly fine and settled weather at Oo-sima, a distance of only 170 miles.
Typhoons occasionally occur in the neighbourhood of Van Diemen Straits and the South of Japan, during the month of June. They seldom happen in July, August, or September. The first half of October may be considered the worst season for them, and it invariably brings us one or more of these terrific storms; they generally travel along the south coast in a north-easterly direction, or over the same track as the Kino-siwo. Captain Maury in his “Physical Geography of the Sea,” says of the cyclones in the Atlantic, that, “they take a westerly course until they fall in with the Gulf Stream, when they turn about and run along upon it until their force is expended.” However applicable this may be to the Gulf Stream, it certainly is not entirely true in reference to the Japan Stream, because the course which typhoons take is frequently from the south-east, crossing the Kuro-siwo at right-angles, and passing on to the north-west; this was the track of the most severe one which we have experienced at Yokohama for many years, and which occurred on the 24th of August 1871. It commenced with the wind from north-east, and the wind continued to blow steadily from that point until after the centre passed, when it came from the south-west.
From June to October, when there is wind from N. E. to S. E. accompanied by rain, and the barometer is steadily falling, these may be taken as almost sure signs of the approach of one of these storms. On observing these signs, it would be prudent for a ship to seek shelter if practicable in one of the numerous harbours on this coast, or, if this be impossible, to take the other alternative and make a good offing. In doing this it should be borne in mind that at such a time as the approach of a typhoon, above all others, the current is least to be depended on, and that its strength would in all probability be greatly increased should the typhoon be coming up from the south-west. On the east coast from the Gulf of Yedo northwards, from October to April inclusive, north-west winds prevail which frequently blow very hard. They are generally accompanied by clear weather, but heavy snow storms are of common occurrence in and near the Straits of Tsugar, and at these times the land becomes completely obscured even during the day. From May to June the winds are variable with a great deal of fine weather. During July and August light south and south-easterly winds may be expected, and about the autumnal equinox the fine weather breaks up. Easterly winds here, as on the south coast, are generally accompanied by bad weather.
The weather in the Japan Sea is much the same as on the east coast. North-west winds are prevalent during the winter. North of the parallel of 40° latitude they commence about the end of September, but the weather continues fine in the southern part of the Sea till the middle of October. Heavy gales, however, occasionally occur here during September and October, the wind commences to blow from south-east and blows very hard between that point and south-west. When it reaches this point it moderates and the weather again clears. These storms seldom last over twenty-four hours. During the summer months southerly winds generally prevail with much fine weather. The Japan Sea is subject to violent squalls from the W.N.W. during the whole year; warning of their approach is however given by the appearance of the sky, or if they occur at night, by the appearance of lightning in that direction. The liability of this sea to these storms should not be forgotten when anchoring in exposed places, such as off Niigata; they blow at times with such force and bring in so heavy a sea, that a ship’s safety may be very much endangered by them.
Fogs commence in the neighbourhood of Yezo, the east Coast of Nipon, and the Gulf of Tartary, as soon as the regular north-west winds terminates, that is about the end of April. They may always be expected in these regions during calms or with southerly winds, that is with any wind that has blown across the warm stream. The period at which they are said to be most dense in the Gulf of Tartary is during the months of June and July. On the west coast they are less frequent, and do not continue so long, while on the south coast they but seldom appear. Winds, however, which come from N. E. to S. frequently bring very thick weather, making navigation at these times almost as hazardous as in a fog. This is always dispersed by N. W. winds.
From what has been stated it will be seen that the strengths, and in some cases the directions, of the currents on these coasts can seldom be calculated upon, and that, when the weather is at all unsettled, no dependence whatever can be placed upon them; that their velocities are sometimes exceedingly great; that a large portion of the coast is, at certain seasons of the year, enveloped in dense fogs, while the remaining portion is, during the continuance of certain winds, subject to weather so thick as almost to equal in density a fog; that gales of wind arise suddenly and not unfrequently; that typhoons are liable to occur at certain seasons; and in addition there are the facts that, in many places, on the southern coast especially, the water is so deep close to the shore that the lead—generally the seaman’s best friend—gives but little warning of the approach to danger, and that outlying rocks and small islands are very numerous. The mariner, therefore, who has to guide a vessel along the coasts of Japan has his vigilance taxed to the utmost, and his skill and judgment put to the severest tests to ensure the safety of the lives and property which are placed under his care.
The minutes of the last general meeting were read and confirmed, and the names of new members announced, as followss:—
Elected at a council meeting held on the 18th of March:—The Hon. C. C. Smith, and Mr. G. P. Ness. Elected at a council meeting held on the 1st of April:—Mr. C. Brennwald, of Yokohama, Messrs. M. O. Flowers, Henry Gribble, H. A. Howe, Junr., Duer, and Hunt, of Nagasaki, Messrs. Edward Dillon, B.A., F.C.S., Wm. Gowland, F.C.S., R. Maclagan, Wm. Smith, C.S., and H. W. Wheeler, of Osaka, Messrs. R. Eusden, J. A. Albinson, Wilson, and Dr. Eldridge, of Hakodate, and Sir John Smale, of Hongkong.
The donations, by Dr. Hepburn of a copy of his Japanese Dictionary, and of $10 from Ch. de Groote, Esq., were acknowledged.
A paper on “Winds and Currents in the vicinity of the Japanese Islands” was then read, in the absence of the author Captain A. R. Brown, by R. H. Brunton, Esq.
The President tendered the thanks of the Society to Captain Brown for his valuable paper.
The Rey. E. W. Syle regretted the absence of the Naval gentlemen whose attendance had been especially invited for this occasion. The subject of currents off the shores and among the islands of Japan was one of the greatest importance; one which possessed also a painful—almost tragic—interest in view of such losses as those of the Hermann, Ariel, Relief and now the Nil. In all these cases the disasters were attributed in great part, to the influence of currents which were powerful though uncertain; and about which there seemed at present to be no reliable or useful knowledge. With regard to the violent currents often encountered in the Inland Sea, especially in the Kino Channel, the Bungo Channel, and the Straits of Shimonoseki, Captain Furber of the P. M. S. S. Co. had been understood to say that the prevalence of southerly or south-easterly winds at some times, and northerly, westerly or north-westerly at others, would determine the sot of currents through these several Channels to the counteraction of all other influences, tidal or otherwise. Captain Furber’s absence was much to be regretted, as his large and recent experience would have enabled him to contribute much valuable information on a subject whose interest was of the most practical and in our circumstances, most painful character.
Mr. Brunton said: “Although Captain Brown is perhaps right in saying that the current always flows to the N. E. at Rock Island, there can be no doubt that, as the China Pilot says, that ebb tide flows E. N. E. and the flood W. S. W. in that locality. While the ebb tide flows with the Japan Stream, the flood tide opposes it. The strength of the tides are very variable, but at certain times they are of great strength. During ebb tide the flow of the Japan Stream is accelerated, and it is no uncommon occurrence to see boats carried past Rock Island at a speed of from three to four miles per hour. During flood tides on the contrary the Japan Stream is retarded, and it is not unfrequently altogether stopped. A conflict then arises between the two Streams, and the effect is that they sometimes neutralize one another. But this conflict causes an extraordinary disturbance in the surface of the water. In places it rises into pinnacle-shaped waves which dance about in all directions; in other places it breaks out into a long line of breakers just as a river torrent does when going over a rapid; and it generally presents the appearance that water does which is considerably over boiling point. I mention this because I have on several occasions gone between Rock Island and the shore in Japanese boats, and have so had very practical opportunities of judging of the state of the sea and of the directions of the current. I have never seen a current at Rock Island setting towards the S. W., but I have seen the water almost stationary, while half way between Rock Island and the shore the flood tide sets to the S. W. with great velocity. It is well known to navigators that with certain winds and at certain times there is a strong set into Suruga Gulf. This set was probably one of the causes which led to the loss of the Nil. Sufficient allowance had not been made for it, and in the thick weather which she experienced she got set to the northwards of her proper course, and ran on shore about twelve miles to the N. W. of Rock Island thinking she was going direct for it. It is the opinion of many nautical men that this northerly set is due to the direction in which the wind blows, and that it only occurs during south-easterly or southerly winds. But to my mind the most feasible way of accounting for it is that the flood tide, which rushes towards the S. W. between Rock Island and the shore, and which impinges on and is mot by the Japan Stream, is turned towards the north immediately after it passed Cape Idsu, and finds a means of egress in the Suruga Gulf. Just in the same way as Captain Brown has explained in his paper, that the Oyasiwa on the Mast Coast where it meets the Japanese Stream is turned towards the West, and has been the cause of so many wrecks in the vicinity of Inaboye.
Captain W. McDonald, being called upon by the Chairman, said that he had arrived too late to hear the paper read, and so could not make any remarks upon it, but that it was many years since he had been in a position to study the subject. What experience he had had in former years was recorded in the Nautical Magazine of 1862–3. With respect to the currents he might mention that on one occasion, after good observations on the previous day, he experienced off the Gulf of Yedo a current of 60 miles E.S.E. in 16 hours.
Mr. J. Pitman said that he had unfortunately arrived too late to hear the whole of the paper read, but must decidedly take exception to the statement that the wrecks of the Hermann, Ariel, Relief and Nil were attributable to the influence of the unknown currents on the Japan Coast. With regard to the Nil there might be, as Mr. Brunton had remarked, a current at times setting out of the Suruga gulf round Cape Idzu into the Gulf of Yedo, but these inshore currents and eddies, dependent as they were on local and tidal influences, were not peculiar to Japan, and a prudent navigator knowing the uncertainty of these inshore currents, in thick and heavy weather would guard against being within their influence. The subject with which the paper treated was one of great general importance, and therefore deserving of close investigation. There could be no doubt that we had but a very imperfect knowledge of the currents on this coast, and he would mention a fact which came under his own observation in February 1871 when on board the S.S. Acantha. She had left Yokohama and having met a strong westerly gale outside was forced to seek shelter under Cape Diamond until the wind moderated. On continuing her westerly course after sunset, expecting to make Rock Island light, she was found at midnight to be inside and close alongside the Redfield rocks and had a very narrow escape of being wrecked. It was only fair to mention that the vessel was only in “ballast trim” at the time.
Mr. W. H. Smith called attention to the fact that there were so few persons present prepared to discuss this very important subject, and raised the question whether it might not be advisable to allow the papers to be laid upon the table for a fortnight before the Meetings at which they were to be read. After some discussion on the subject, he moved that the matter be referred to the Council for decision. This motion was seconded by Mr. Pitman, but on being put to the meeting, was lost. Mr. Brunton suggested that the papers should be read by the author at one meeting and discussed at the following meeting. This would meet all views which had been expressed and was very often done at home. At length, the following Resolution, moved by the Rev. Mr. Syle and seconded by Sir H. S. Parkes was carried. “That when practicable the papers about to be read shall lie on the table in the Society’s Library for the perusal of Members.”
Mr. Von Brandt then favoured the Meeting with an interesting description of the custom of tattooing as practised in this country; and a short discussion of the subject followed in which Sir H. S. Parkes, Captain McDonald and Captain Bridgford joined.
The Meeting adjourned at about a quarter past ten.