Summarizing the dimension of a war in the seas will always remain incomplete. It must remain incomplete if not military aspect of enemy destruction is in focus but the temperature and salinity structure of sea water levels. Seas look always the same, before a ship arrives on scene, and after it has left scene, before a sea battle, and after a battle has just ended. Any sign or track left on the water’s surface by ship movement, exploding sea mine or sinking ship disappears quickly. Only oil and cargo may disturb the picture of unadulterated nature for a short while. Any scenery of action is back to eternal expression very soon.
structure of any ocean scene left after anthropogenic action has changed
its structure in one way or the other. The physical composition of the
sea bodies concerning temperature structure and salinity distribution
has inevitably changed. They never turn back to their previous
state but strive for a new equilibrium. Some call it a state of chaos,
but it is plain physics. This physics, which run the oceans, make
War at sea in the Atlantic, 1939-1941
Naval war and supply across the seas became part of the ocean physics for some time. Allies sailed 300,000 vessels across the North Atlantic. If every ship turned the sea about on a width of 20 meters, the total sums up 6 Million meters, or 6,000 km. This means that, over a corridor wide as from Glasgow to Lisbon, respectively Boston to Miami, the sea surface of North Atlantic was ploughed through three times. Naval Escort Vessels and freely operating war ships certainly doubled the space of ‘turnover’. Many thousands of torpedoes, many hundred thousands of depth charges and bombs, and multi-millions of shells certainly doubled again the already ‘doubled space’ of turnover the middle North Atlantic. The surface layer was completely ‘churned and turned’ presumably not less than a dozen times in just over six years. Any ‘turning’ effect could reach down to a few meters, five to ten meters (vessel draught), 200-300 meters (depth charge), thousands of meters (sinking ships, cargo, ammunition, etc).
As mid-latitude seasonal climatology heavily depends on the upper sea surface layer of about 30-60 meters, global naval war is a force to reckon.
The issue of climatic change during WWII has two distinct periods, viz. the period before Pearl Harbour and the one thereafter. From September 1939 until early 1942, naval warfare was largely confined to European waters. Great climatic relevance of the war at sea in the Northern Europe became dramatically clear during the extremely cold winters of 1939/40, 1940/41, and 1941/42.
Outside Europe’s waters, naval activities during 1940 and 1941 were largely confined to Eastern North Atlantic. The most affected areas were the transportation routes from Britain to North America, and the routes from Britain to Gibraltar and Dakar.
U-boats in the Atlantic
A number of German U-boats were already in the Atlantic when the war started, in September 1939. Britain introduced rapidly the convoy system. A convoy consisted of up to sixty, either slow or fast vessels, accompanied by up to ten naval escort ships. The first convoy sailed in September. Also in September 1939, groups of three to five naval vessels were formed to control large areas in the North Atlantic. These groups criss-crossed the seas day and night, searching for U-boats and dropping depth charges when a U-boat was detected or assumed to be around. Also German surface naval vessels, like battleships Deutschland, Scharnhorst and Gneisenau, sailed in the Atlantic with a number of escort vessels. Until the end of December 1939, the Allies and Neutrals lost 55 vessels with a total tonnage of 300,000 in the Atlantic. Five U-boats were also sunk.
Fighting in the North Atlantic increased during the war years 1940 and 1941. In August 1940, Germans lifted all restrictions on U-boat targets. The number of available U-boats was of 50 (January 1940) and of 230 (December 1941), out of which about 8 were on permanent missions in the Atlantic during 1940, and 15 during 1941. The total loss inflicted on British, Allied and Neutral shipping in the Atlantic by the Axis powers (U-boats, air force, mine, and surface naval vessels) was of 3 million tons in 1940 and of 4 million tons in 1941. These figures relate about 1,500 ships, with cargo, stores and fuel. The Germans lost about 40 U-boats in the Atlantic during these two years.
To win the war, effective supply was essential. Thousands of accounts have been written about the dramatic events at sea. On the 21st/22nd of September 1940, Convoy HX72 was caught in a twelve-hour battle, in which eleven ships were sunk and two damaged, with a total loss of 100,000 tons of supplies and of 45,000 tons of fuel.
During the early times of the war, convoy escort was small in number and was not always staying with the group for the full travel distance. By 1941, the average size of a convoy was of about forty ships, with six naval vessels as escort. Later, some escorts became quite massive. For example, in 1942, the Convoy ON202 with 38 merchant ships had an escort of 3 destroyers and 3 corvettes; while the escort for the Convoy ONS18 comprised 6 destroyers, 8 corvettes, and one trawler.
A special aspect concerns the loss of tankers from 1939 until 1941. British fleet lost 1,469 tank-ships and Norwegians, 430 in just 28 months. If one assumes that the average loading capacity of each ship was of 2,000 cargo tons and that half of the sunken vessels were laden, the total oil spill could sum up to two million tons in 2 years, an amount corresponding with the total of all major tank ship oils spills in 1967-2002.
However, U-boats were not acting alone in the North Atlantic. Since the Luftwaffe could operate out of France since the summer of 1940, long-range aircrafts were sent out into the Atlantic to attack supply routes. The total shipping tonnage sunken by Axis airplanes in all sea areas during the first two war years is claimed to be of 1.5 million tons.
War at sea in the Pacific: 1942 -1945
the 8th of December 1941, The New York Times reported:
Yesterday morning, Japan attacked the United States at several points in
the Pacific, with a major attack on Pearl Harbour. President Roosevelt ordered United States forces into action and a declaration of war was
expected soon. Seven hostile actions from a naval ship off the coasts of
San Francisco to Malaysia were reported
clash of the naval forces in the Pacific had no precedent. The fighting
included all means and military options. Heavy battles were fought. In
May 1942, the combatants had already met in the Coral Sea each with
three-dozen ships and several hundred airplanes. On the 5th
of May, in a first attack, the US Navy destroyed one Japanese destroyer,
three minesweepers, and 4 smaller vessels, with 22 torpedoes and 76
bombs (each weighing 450
Aircrafts played a significant role in the Pacific war. Japan’s front line strength was its air power consisting of about 4,000 planes; the USA had 4,000 in January 1941 and 22,000 in July 1945. After taking over Okinawa, the US Third fleet had deployed 26 aircrafts carriers, 64 escort carriers and 14,000 combat aircraft for a final attack on Japan. Japanese loss of combat aircraft was of 37,000 (army and navy); the USA lost 8,700 in the battle. Material loss in that battle was gigantic. Japan lost more than 500 warships (including 150 submarines), with a total tonnage of about 2,000,000, the figure in merchant tonnage was about 8,000,000 of which 5 Mio (1,150 ships) have been sunk by US-submarines and 1.5 Mio by airplanes. A special chapter could possibly be written on the sinking of tanker tonnage resulting in oil spills. During the war years Japan had some 700,000 tonnage permanently afloat and lost over the war period 1,500,000 tanker tonnage. The US lost 52 submarines. Many of them fell pray to depth charges. Standard Japanese depth charge contained about 230lb of explosives. Anti-submarine bombs carried by aircraft were 131lb and 550lb each, the latter being preferred when available. The Japanese had no means of determining the depth of a submarine to be targeted and so the pattern of attack usually was dropping of depth charges with a variety of settings on the time fuse. The Japanese lost 150 submarines, many of them to depth charges. It is necessary to consult special literatures available in great number and detail even to imagine what happened in the Pacific war theatre. One cannot help getting the impression that WWII left its imprint on Pacific seawater body.
War in the Atlantic: 1942 –1945
Aerial warfare over the Atlantic
The use of planes in the Atlantic war made tremendous headway since the USA entered the war after Pearl Harbour attack, in December 1941. The US production was estimated at 127,000 planes in 1942, exceeding the total number of German aircraft production during the whole war period. It meant that more aircraft with much better quality and capability were available for surveillance, bombing and combat missions in the Atlantic. In August 1942, only eighteen American B-24 aircraft, called ‘Liberator’, were available for Atlantic convoys. These planes had a range of 2,400 miles, fuel tanks of 2,500 gallons and reached heights of 30,000 feet. From winter 1942/43 onward, long-range aircrafts were assigned for anti-submarine warfare in the Atlantic. They sank 33 submarines between April 1943 and September 1944. 209 long-range bomber aircrafts were available for the US navy in July 1942. The number increased progressively up to 2,200 searching and chasing U-boats, between June 1943 and May 1944.
Vice-versa, U-boats got very little support from the Luftwaffe in 1942 and 1943 but even that little help diminished after D-Day (1944), while the Allies’ air force presence in the Atlantic improved impressively. The British Coastal Command flew approximately 238,000 sorties, totalling 1,300,000 flying hours. Fourteen U-boats were confirmed to have been destroyed by Coastal Command and another twelve damaged.
German Luftwaffe had not been well equipped to put up a significant performance in the North Atlantic battle. However, they had in service a few hundred long-range four-engine planes, which flew from bases in France, in 1941. During the month of August 1941, they succeeded in sinking more than 300,000 tons of shipping, i.e. almost one-third more than the U-boats sank in the same month. Axis airplanes shall have sunk a total of about 800 merchant ships in all war theatres. Even if less than half of that number has been sunk in the sensitive waters of the Northern Atlantic and Northern Pacific, it actually meant the use of many thousands of bombs and the felling of hundreds of planes in the oceans as well.
U-boats off Florida and Cape Hatteras - 1942
There was a short period, from January until June 1942, when U-boats operated extremely successfully along America’s East coast. Within half a year, they had sunk about 400 vessels. In two weeks, a handful of U-boats could sink 25 ships with a total tonnage of 200,000, of which 70% were tankers. In the summer of 1942, U-boat operation ‘Paukenschlag’ (Drumbeat) ended. The US Navy had become effective. The Gulf Current flows from Florida to Cape Hatteras, before turning at Cape Hatteras into the Atlantic to go eastwards, to Europe. The warm current on one hand and the colder Atlantic water off Cape Hatteras on the other built a highly sensitive water body which had a significant impact on daily weather, seasons and climatic conditions in the Northern Hemisphere. Waging a war at sea in these waters is presumably effective in producing changes to the seawater sphere.
In August 1942, the U-boat fleet had reached the number of 340, with almost 300 boats more than three years before. During the whole war period, the U-boat force had comprised about 1,100 boats, from which 850 participated in at least one combat mission and 630 were destroyed in enemy attacks.
Loss incurred by German U-boats attacks (all told) is of 2,822 vessels (14,220,000 tons). 152 Italian boats sank 132 vessels (700,000 tons). Axis U-boat fleet (German, Italian, Japan) is credited with the sinking of 25 big naval vessels, 41 destroyers and about 150 other naval vessels. The main field of operation of the U-boats was the Atlantic. They were quite successful only from 1942 until March 1943.
As already mentioned above, the Allies completed over 300,000 Atlantic voyages during this period of the war. The heroic story of merchantmen has been told and re-told in uncountable essays and books. Here is only one case.
In March 1943, two convoys, viz. SC122 and HX229, encountered forty-four U-boat attacks on their route. During the three-day battle that ensued, twenty-three merchantmen from the two convoys were killed. At the same time, convoy HX229A, which included thirteen tankers, eight refrigerators and four cargo liners (39 ships), was routed northeast, towards Greenland. There they came upon Arctic conditions. Three convoys with a total of 131 ships carried about 1,000,000 tons of cargo – petroleum fuel, frozen meat, food, tobacco, grain, timber, minerals, steel, gunpowder, detonators, bombs, shells, lorries, locomotives, invasion barges, aircraft and tanks.
The destiny of many tankers proved extremely disastrous for their crew and presumably for the ocean area, too. The Allied and Neutral countries had about 1,000 tankers in their permanent service since 1942. Between December 1941 and May 1944, the loss of tankers with a size over 1,600 tons was of 4,221 ships.
Report 1 (extract):
October 1941: “Attacking from inside the convoy between the seventh and the eighth column, U-432 torpedoed the Norwegian tanker Barfonn. U-558 destroyed British W.C.Teagle and Norwegian Erviken, both laden with aviation spirit. Tankers could merit the description of ‘floating volcanoes’.
Report 2 (extract):
The 15th of November 1942: “Shortly after 3.00 a.m. all hell was let loose. The Avenger was hit by two torpedoes and, being little more than a large floating petrol can, it blew up instantly in a sheet of flame… An enormous bright red glowed on the near horizon where Avenger blew up”.
Report 3 (extract):
1942: To the southwest of Ireland, the convoy SC107 lost fifteen merchantmen from its forty-two vessels, during the last week of November. The attack came from a pack of sixteen U-boats. After sinking two vessels and the Empire Linx, U-132 was on target for being bombed by a Liberator of 120 Squadron. Then, from beneath the water came a tremendous explosion: Empire Linx, an ammunition ship, blew up. It is assumed that U-132 was within lethal range and thus became a victim of its own victory.
Report 4 (extract):
1941: Sugar carrier Silvercedar had been loaded in New York with high explosives in the holds and bombers on deck. Amidst the wind gale of 8-9 Beaufort, a torpedo struck her in hold No.3 which was loaded with condensed milk. Silvercedar blew up with a mighty explosion and sank in less than two minutes.
One of the most effective means of penetrating deep below the sea surface is the depth charge. Depth charges, which could explode at a depth of 500 feet, were in use since 1942. The ‘Hedgehog bomb’, a highly powered explosive fired by a multi-barrelled mortar and filled with Torpex, was also in use. Its range was of 250 yards ahead of the escort vessel. Attacking ships, it could fire twenty-six depth charges in pairs, set to explode at 500 feet and 740 feet alternately, at intervals of ten-second, whilst continuing to steam ahead of the U-boat.
Report 5 (extract):
1941: U-94 came upon the convoy and sank two ships, then suffered damage from the depth charge counterattack of Amazon, Bulldog and Rochester. The battle lasted four hours. Attacker account said eighty-one depth charges were used, but the U-boat commander acknowledged only sixty-seven.
Report 6 (extract):
March 1944: On the 29th of February, frigates Gore, Garlies, Affleck and Gould attacked U-358 with depth charges and Hedgehogs. They held contact virtually continuously until next day, the 1st of March, but although they made one ‘creeping attack’ of 104 depth charges, which detonated like ‘a marine convulsion’, their enemy lay very deep, very low and very stubborn. Hunt was carried on for thirty-eight hours. How many depth charges the three frigates eventually dropped in total is not mentioned. It seems it could go into many hundreds.
It seems difficult to obtain reliable figures concerning the number of depth charges dropped in the Atlantic. The total figure could be as high as 500,000 or even more.
Due to experience in WWI, transport ships were equipped with guns to defend against U-boats and surface raiders. Within 12 months of war, 3,000 vessels were armed with a 4.7-inch gun manned by trained gunners, usually six.
Report 7 (extract):
A Focke-Wulf bomber attacked the Orient City, sailing in a convoy, at night. The gunner trained his gun as the aeroplane approached and flew straight into the shell-burst. The aircraft’s engine stopped as if switched off suddenly. It fell into the sea like a giant leaf. As it crashed, its bomb-load, intended for the Orient City, exploded.
Russians received about 4,000,000 tons of cargo, including 7,000 aircrafts and 5,000 tanks, via the most difficult and dangerous route from Britain to Murmansk. It was climatically the most sensitive sea route, presumably many times more effective for climate changes then naval activities, one thousand miles further south. Out of the total cargo shipped, 7% was lost at sea. Danger came not only from the arctic climate during most of the year, but from the attacks of the German Navy and Luftwaffe from their bases in North Norway as well. At peak time, the Luftwaffe had 264 aircrafts in the area, while the British Fleet Air Arm and the Royal Air Force flew 17 combat missions to North Norway, form January 1942 until November 1944, involving a total of 600 airplanes.
Convoys started to sail in August 1941; the 35th convoy sailed in May 1945. Convoys guarded a total of 715 ships. The loss of merchant ships was of 100, with 600,000 tons. The German side lost five surface naval ships, including a battle ship, a battle cruiser and 32 submarines. British Navy lost 20 surface vessels and one submarine.
To avoid the confrontation with the German forces, the convoys sometimes travelled far to the North. For example, in July 1942, the ships of convoy PC17 navigated close to Edge Island (Spitsbergen) 77°N, at the edge of the ice border, but were still attacked by aircrafts of the Luftwaffe and by U-boats. Few years later, it was observed that a deep fall in temperatures occurred at Franz Josephs Land (80°N, 53°E), in 1950, with over 5°C in one decade after the mean temperatures varied between -10°C and -11°C from 1936 until 1950.
Report 8 (extract):
An anti-aircraft gunner, on service on the high-octane tanker, the steamer Bolton Castle which was sunk by the ill-fated Arctic Convoy PQ17, reported: “We were sunk in the ice fields and the ship sank in thirteen minutes. Sunken by three bombs of a Junker 88, the Bolton Castle, which had hundreds of tons of cordite in cargo hold 2, looked ‘like a giant Roman candle’.”
Out of the 35 cargo ships and three rescue vessels of the convoy PQ17, only 11 vessels and two rescue ships survived.
The convoys were escorted by a considerable number of naval ships. Fighting East and West of the North Cape produced some of the hardest fought battles of WWII. For the Norwegian and Barents Sea, the military presence will not have passed by without any impact on the sea.
Atlantic Sea Mines
The strong barrage of 110,000 mines laid by Britain between Orkney and Iceland, from 1940 until 1943, received little notice. The mines ‘Mk XX’ were supposed to prevent U-boats from reaching the shipping routs in the Atlantic. Whether the barrage was a serious threat to U-boats or not we do not known, but it seems not. It would have been a tremendous threat to the sea if the mines tended to explode prematurely.
It is not clear what happened to the mine barrage after the end of the war. Were the mines ‘gone’ by 1945? Were remaining mines swept after 1945? The British deployed 300 minesweepers on the assumption that it would take 549 days to clear moored mines and 676 days for ground mines around its coast. The Germans also tackled the issue of deployment with about 400 minesweepers.
Even though only very little information about the naval warfare between 1942 and 1945 could be conveyed in such a brief presentation, it is hoped to be informative enough to raise the awareness that oceans had been ‘stirred and shaken’ in a way that could have caused their extra normal cooling for four decades.
 Source: www.pmel.noaa.gov/