Editing White Sea (section)

==Geography==
{{see also|White Sea Rift System}}

===Extent===
The [[International Hydrographic Organization]] defines the northern limit of the White Sea as "A line joining [[Cape Svyatoy Nos, Murmansk Oblast|Svyatoy Nos]] ([[Murmansk Oblast|Murmansk]] Coast, 39°47'E) and [[Cape Kanin]]".<ref>{{cite web|url=https://iho.int/uploads/user/pubs/standards/s-23/S-23_Ed3_1953_EN.pdf|title=Limits of Oceans and Seas, 3rd edition|year=1953|publisher=International Hydrographic Organization|access-date=28 December 2020}}</ref>

===Topography===
[[File:Severodvinsk Yagry Island Beach.jpg|thumb|Summer day on a beach near [[Severodvinsk]], on the southeastern shore of the sea]]
[[File:Кандалакшский залив.jpg|thumb|[[Kandalaksha Gulf]]]]
[[File:Kiy-island Russia.jpg|thumb|Shore of Onega Bay on [[Kiy Island]]]]
There are four main bays or gulfs on the White Sea. These bays connect with the funnel-shaped opening to the Barents Sea via a [[White Sea Throat|narrow strait]] called "[[White Sea Throat|Gorlo]]" ({{langx|ru|Горло}}, meaning "throat"). [[Kandalaksha Gulf]] lies in the western part of the White Sea; it is the deepest part of the sea, reaching 340 metres (1,115 feet). On the south, [[Onega Bay]] receives the [[Onega River]]. To the southeast, the [[Dvina Bay]] receives the [[Northern Dvina]] at the major port of [[Arkhangelsk]]. On the east side of the 'gorlo', opposite to the [[Kola Peninsula]], is [[Mezen Bay]]. It receives the [[Mezen River]] and the [[Kuloy River (White Sea)|Kuloy River]]. Other major rivers flowing into the sea are the [[Vyg River|Vyg]], [[Niva River|Niva]], [[Umba River (Russia)|Umba]], [[Varzuga River|Varzuga]] and [[Ponoy River|Ponoy]].<ref name=bse/><ref name=brit/>

The seabed of the central part and Dvina Bay is covered in [[silt]] and sand, whereas the bottom of the northern part, the [[Kandalaksha Gulf]] and Onega Bay is a mixture of sand and stones. Ice age deposits often emerge near the sea shores. Northwestern coasts are tall and rocky but the slope is much weaker at the southeastern side.<ref name=bse/>

The White Sea contains a large number of islands, but most of them are small. The main island group is the [[Solovetsky Islands]], located almost in the middle of the sea, near the entrance to Onega Bay. [[Kiy Island]] in Onega Bay is significant due to a historic monastery. Velikiy Island, located close to the shore, is the largest island in the Kandalaksha Gulf.<ref name=brit/>

===Hydrography and bathymetry===
The White Sea is a water-filled depression in the block of a continental shelf known as the [[Baltic Shield]]. Its bottom is very uneven and contains the Kandalaksha Hollow in the northwest and the Solovetsky Islands in the south. Also, the Onega Bay has many small underwater elevations. The opening and the ''gorlo'' of the sea are rather shallow, with depths about 50 metres or less. There is an underwater ridge in the northern part of the ''gorlo'', resulting in maximum depths of 40 metres in that part. This hinders water exchange between the White and Barents seas.<ref name=brit/><ref name=rev/> The exchange is assisted by the [[tide]]s, which are semidiurnal (rising twice a day), with the amplitude increasing from 1 metre on the south to 10 metres in Mezen Bay. Currents are rather weak in the open seas with the speed below 1&nbsp;km/h, but they significantly strengthen in the bays.<ref name=bse/> The tidal waves are much faster than the regular currents and reach the speeds of 9&nbsp;km/h in Mezen Bay, 3.6&nbsp;km/h in Onega Bay and 1.3&nbsp;km/h in the Kandalaksha Gulf.<ref name=rev/>

Rivers bring annually about 215&nbsp;km<sup>3</sup> of fresh water, on average, mostly to the Onega, Mezen and Dvina bays. The Northern Dvina alone may contribute up to 171&nbsp;km<sup>3</sup> in some years, with the Mezen, Onega, Kem and Vyg rivers adding up to 38.5, 27.0, 12.5 and 11.5&nbsp;km<sup>3</sup>, respectively. About 40% of this volume is brought during the snow melting in May, and the inflow is minimal in February–March. This inflow raises and lowers the sea level that promotes the water exchange with the Barents Sea. As a result, annually, about 2,000&nbsp;km<sup>3</sup> and 2,200&nbsp;km<sup>3</sup> flow in and out of the White Sea, respectively. The inflow of fresh water in spring decreases the surface salinity in the top 5–10-metre layer to 23‰ (parts per thousand) in the eastern and 26–27‰ in the western parts of the sea, reaching 10–12‰ in Dvina Bay; it also increases the content of [[silicon]] and [[silicate]]s in water, which is a characteristic feature of the White Sea.<ref name=rev/>

Storms are the strongest in October–November. Shallow sea depths reduce the wave height to the average of 1 metre, sometimes reaching 3–5 metres. The sea is quiet in July–August.<ref name=rev/>

===Climate===
[[File:modis white sea.jpg|thumb|right|Two satellite photos of the White Sea taken on 23 April 2000 (top) and 3 May 2001 (bottom)]]
The climate varies between [[Polar climate|polar]] and [[Subarctic climate|subarctic]] with frequent fogs and clouds. Winds are predominantly southwestern in winter with speeds of 4–8&nbsp;m/s. They bring cold air from the south, establishing the temperature of about −15&nbsp;°C (February) over most of the sea. The northern part is warmer at about −9&nbsp;°C, sometimes reaching −6&nbsp;°C, due to the warm air masses from the Atlantic. Arctic anticyclones, however, change winds to the northeastern ones, bringing much colder weather with temperatures of about −25&nbsp;°C. Summers are cold, cloudy and relatively humid, with northeastern winds and frequent rains. Average July temperatures are 8–10&nbsp;°C. Occasional southeastern winds bring warm air from Europe, raising the temperature to 17–19&nbsp;°C and sometimes even to 30&nbsp;°C. Annual precipitations increase from 282&nbsp;mm in the north 529 in the south.<ref name=bse/><ref name=rev/>

In winter, from October–November to April–May, the sea freezes, with the average January water temperatures of −1.9&nbsp;°C in the north, between −1.3 and −1.7 °С in the centre, and between −0.5 and −0.7 °С in the bays. These variations are due to the distribution of water salinity across the sea, which increases from 24 to 26‰ in the centre to 30.5‰ in the ''gorlo'', reaching 34.0–34.5‰ toward the Barents Sea. The freezing period varies from year to year as shown in the satellite image to the right.<ref name=bse/> The ice is not stationary, but 90% of it is floating and is continuously removed to the Barents Sea. Ice thickness is usually about 40&nbsp;cm but may reach 150&nbsp;cm in cold winters.<ref name=rev/>

In summer, surface water warms up to 15 °С in the central part, but remains relatively cold in the north, at 7–8 °С, due to the water exchange between the surface and the cold bottom part which is enhanced by the shallow depths in the northern parts. Deep sea (about 100 m or more) is characterised by stable temperature (−1.4 °С) and salinity (30‰).<ref name=bse/><ref name=rev/> The depth distribution of water temperature is very inhomogeneous across the sea. For example, at the exit from Dvina Bay, water temperature drops to 0&nbsp;°C at the depth of only 12–15 m, but the same temperature is reached at 65 m at the exit from the Kandalaksha Gulf.<ref name=rev/>