The Dardanelles is a narrow strait in northwestern Turkey, 61 km (38 mi) long and between 1.2 and 6 km wide, that links the Aegean Sea to the Sea of Marmara and so, with the Bosporus, forms the only sea route between the Mediterranean and the Black Sea. It separates the Gallipoli peninsula in European Turkey from the Troad in Asian Turkey, averages 55 m deep and reaches 103 m at Nara Burnu, its narrowest point abreast the city of Çanakkale. Known in antiquity as the Hellespont, it matters because every ship moving between Black Sea ports such as Novorossiysk and the open ocean must pass through it, and because the land on either side can command that traffic, which is why the strait was fought over from Xerxes in 480 BC to the Gallipoli campaign of 1915.
The strait does not look the same from one season to the next. Its currents, its weather and the calendar of events on its shores all follow the year, so the clearest way to understand it is to follow that year round, month by month, from the wet winter at Çanakkale to the dry summer when swimmers cross it.
Winter on the Çanakkale Narrows: December to February
Winter is the wet season on the Dardanelles. The Turkish State Meteorological Service records an average of 100.4 mm of rain at Çanakkale in December, the wettest month of a year that totals about 620 mm, followed by 78.6 mm in January and 76.3 mm in February. The mean temperature in January is 6.5 °C, and the city's record low, −11.5 °C, was set on 2 February 1929. Wikipedia's climate summary notes that the winds here are strong all year but strongest in the winter months, which matters on a waterway that is already among the most crowded and difficult to navigate in the world. Sailing ships historically waited at anchor for the right conditions before entering, because the currents set up by the Black Sea and the Sea of Marmara run hard through the narrow, winding channel.
Winter is also when the Gallipoli campaign ended. Through late 1915 the Allied troops on the peninsula endured a three-day downpour at Suvla and then a blizzard in early December. The British Cabinet confirmed the decision to evacuate in early December; the last troops left Suvla and Anzac before dawn on 20 December, and the final British soldiers departed Lancashire Landing at Cape Helles around 04:00 on 8 January 1916. The campaign, which had begun with naval operations on 19 February 1915, had cost roughly 250,000 casualties on each side.
More recently, a winter date has marked a change in how the strait is used. In February 2022, at the start of Russia's invasion of Ukraine, Turkey closed the Dardanelles to all foreign warships under the Montreux Convention of 20 July 1936, the treaty that still governs the Turkish Straits. Commercial shipping continued to pass, as the convention requires in peacetime.
18 March: Erenköy Bay, the Nusret's Mines and a Bridge Opening
The single most important day in the strait's modern history falls at the end of winter. In the weeks before 18 March 1915, the Ottoman minelayer Nusret laid a new line of mines (20 in the British account, 26 in the ship's own history) across the head of Erenköy Bay, a wide bay on the Asian shore just inside the entrance, where British ships had been seen turning to starboard as they withdrew. The mines were moored at 15 m and spaced about 91 m apart. The Allied fleet, arranged in three lines of battleships, two British and one French, attacked the forts of the Narrows the next day without knowing they were there.
At 13:54 the French battleship Bouvet turned into Erenköy Bay, struck a mine and capsized within minutes; 639 of her crew died and only 48 survived. The battlecruiser Inflexible hit a mine near the same spot around 16:00 and had to be beached on Bozcaada (Tenedos). HMS Irresistible was mined next, and at 18:05 HMS Ocean, sent to help, struck a mine as well; both were abandoned and later sank. The failure of the naval attack led directly to the land invasion of the Gallipoli peninsula.
The defences the fleet faced stood on a site fortified for centuries. Kale-i Sultaniye on the Asian shore and Kilitbahir, the "lock of the sea", on the European shore were built under Mehmed II in 1463 to cover the narrowest point, where barely 1.2 km of water separates them; the Asian fortress, Sultaniye, gave Çanakkale its name. On 18 March 2022, the 107th anniversary of the naval battle, Turkey opened the 1915 Çanakkale Bridge between Lapseki and Sütlüce, about 10 km from the Sea of Marmara. Its main span of 2,023 m makes it the longest suspension bridge in the world, and it is the first fixed crossing of the Dardanelles.
April and May: Dawn at Anzac Cove and Byron's Crossing
Spring brings rain down to 49 mm in April and 32 mm in May, and average temperatures rise from 12.8 °C to 18 °C. It also brings the strait's busiest season of remembrance. Landings planned for 23 April 1915 were postponed by bad weather until 25 April, when British and French troops went ashore at Cape Helles and Australian and New Zealand troops at Anzac Cove. The anniversary, Anzac Day, is a national day of remembrance in Australia and New Zealand, and a dawn service is held on the peninsula itself, first at the Ari Burnu War Cemetery and, since the 2000 service, at the larger Anzac Commemorative Site on North Beach. Total deaths in the campaign included about 41,000 British and Irish, 15,000 French, 8,700 Australians, 2,700 New Zealanders, 1,370 Indians and 49 Newfoundlanders, and roughly 60,000 Turkish soldiers.
The Turkish side of that story is told at the Çanakkale Martyrs' Memorial on Hisarlık Hill above Morto Bay, at the southern tip of the peninsula, which commemorates about 253,000 Turkish soldiers who served in the campaign. Its foundation stone was laid on 19 April 1954 and the main structure was completed on 15 March 1958. It stands inside the Gallipoli Peninsula Historical Site, a protected area of more than 33,000 hectares established in 1973.
A gentler spring anniversary belongs to 3 May 1810, when the poet Lord Byron swam the Hellespont from Europe to Asia, a crossing that recreated the myth of Leander, who swam the strait each night to meet the priestess Hero until he drowned in a storm. Swimmers repeat Byron's crossing every year as an open-water event.
Spring can also show the strain on the water the Dardanelles carries. In 2021 the Sea of Marmara, which feeds the strait's surface current, suffered a mucilage outbreak, a thick, sticky layer that lasted from January until June, damaging habitats and disrupting fishing. The Marmara basin holds about a third of Turkey's population, and decades of poorly treated waste have put heavy pressure on it.
June to August: Two Currents Under a Dry Sky
Summer on the strait is close to rainless. Çanakkale averages 27.3 mm in June, 12.9 mm in July and just 6.8 mm in August, the driest month, when the mean temperature reaches 26 °C; the city's highest recorded temperature, 39.7 °C, came on 1 August 2021. With the rain gone, the strait's real engine is easier to see, because it does not depend on local weather at all.
Two layers of water move through the Dardanelles in opposite directions. On top, a surface current carries the fresher water of the Black Sea and the Sea of Marmara out towards the Aegean; beneath it, a denser, saltier undercurrent flows back in from the Mediterranean. The contrast is sharp: the surface of the Marmara averages about 22 parts per thousand of salt, while its bottom water averages around 38, close to the Mediterranean. The net flow is out of the Black Sea, fed by its rivers, but water is always moving both ways at once, in what oceanographers call estuarine circulation.
High summer has its own political date. The Montreux Convention Regarding the Regime of the Straits was signed on 20 July 1936, restoring Turkish control and the right to remilitarise the shores after the Treaty of Lausanne of 1923 had required them to stay demilitarised. Under it, civilian ships pass freely in peacetime, while warships of non-Black Sea states face limits on number, tonnage and length of stay, and Turkey must be notified in advance.
September to November: Autumn Rains and the Year's Turn at Sea
The rains return in autumn: 24.2 mm in September, then 67.5 mm in October and 79.2 mm in November, as average temperatures fall from 21.6 °C to 12.3 °C. Passenger and vehicle ferries cross the strait daily in every season, and commercial shipping never stops: tankers carrying Russian oil from ports such as Novorossiysk, and cargo for Ukraine and the other Black Sea states, have no other sea route to the Mediterranean, whatever the month.
Beneath the water, two 400 kV power cables now cross the strait between landing stations at Lapseki and Sütlüce; the first was switched on in April 2015 and carries 2 GW over 3.9 km of seabed, crossing four fibre-optic lines laid earlier along the channel. On the hills above, the northern shore along the Gallipoli peninsula stays sparsely settled, while the southern shore holds Çanakkale's urban population of about 110,000.
Autumn is also a good time to see why the ancient world cared so much about this channel. The site of Troy lies near the strait's western entrance on the Asian side, and in about 482 BC, according to Herodotus, Xerxes I built two pontoon bridges across the Hellespont at Abydos so his army could march into Greece in 480 BC. When a storm destroyed them, he is said to have had the water given 300 lashes. Alexander the Great crossed in the other direction in 334 BC. Under the Byzantine emperor Anastasius I in the 6th century, merchants paid set fees here; a marble plate in the Istanbul Archaeological Museum records them, down to 6 follis for each wine merchant bound for Constantinople.
The water year ends where it began, with Black Sea water sliding over Mediterranean water through a channel little more than a kilometre wide at Çanakkale. For the land war fought along its northern shore, read our guide to the geography of the Gallipoli peninsula; to follow a ship onward, continue across the Sea of Marmara to the second of the Turkish Straits, the Bosporus at Istanbul.