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Mälaren

Coordinates:59°30′N17°12′E/ 59.500°N 17.200°E/59.500; 17.200
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Mälaren
View of Mälaren
Lake Mälaren at dusk
Location in Sweden
Location in Sweden
Mälaren
LocationSweden
Coordinates59°30′N17°12′E/ 59.500°N 17.200°E/59.500; 17.200
Primary outflowsNorrström
BasincountriesSweden
Surface area1,140 km2(440 sq mi)
Average depth13 m (43 ft)
Max. depth64 m (210 ft)
Water volume14 km3(11,000,000 acre⋅ft)
Surface elevation3 metres (9.8 ft)
IslandsSelaön,Svartsjölandet(seelist)

Mälaren(UK:/ˈmɛlərɛn/MEL-ər-en,US:/ˈmeɪlɑːrən/MAY-lar-ən,[1][2][3]Swedish:[ˈmɛ̂ːlarɛn]ⓘor[ˈmɛ̂ːlaɳ]),[4]historically referred to asLake Malarin English, is the third-largest freshwater lake inSweden(afterVänernandVättern). Its area is 1,140 km2(440 sq mi) and its greatest depth is 64 m (210 ft). Mälaren spans 120 km (74.6 mi) from east to west. The lake drains, from south-west to north-east, into theBaltic Seathrough its natural outletsNorrströmandSöderström(as it flows aroundStadsholmenisland) and through the artificialSödertälje CanalandHammarbyledenwaterway. The easternmost bay of Mälaren, in centralStockholm,is calledRiddarfjärden.The lake is located inSvealandand bounded by the provinces ofUppland,SödermanlandandVästmanland.The two largest islands in Mälaren areSelaön(91 km2(35.1 sq mi)) andSvartsjölandet(79 km2(30.5 sq mi)). Mälaren is low-lying and mostly relatively shallow.

Being a quite narrow and shallow lake, Mälaren has bridge crossings betweenEskilstunaandVästeråswith two crossings on the western end atKvicksundand three separate bridges betweenSträngnäsandEnköpingin the central part of the lake. On the eastern end, the entirety ofEkerö Municipalityis set on islands within Mälaren. That urban area also has a bridge connection to the mainland in Stockholm along with bridges between various islands in the municipality.

TheViking AgesettlementsBirkaon the island ofBjörköandHovgårdenon the neighbouring islandAdelsöhave been aUNESCO World Heritage Sitesince 1993, as hasDrottningholm Palaceon the island ofLovön. The barrow ofBjörn Ironsideis on the island of Munsö, within the lake.

The barrow of Björn Ironside (Björn Järnsidas hög) on the island of Munsö, in lake Mälaren,Sweden.The barrow is crowned by a stone containing the fragmentedUppland Runic Inscription 13.

Etymology

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Theetymologicalorigin of the nameMälarenstems from theOld Norsewordmælirappearing in historical records in the 1320s and meaninggravel.[5]The lake was previously known asLǫgrinn,which isOld Norsefor 'The Lake'.[6]

Geology

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See also:Central Swedish lowland
Mälaren details, withStockholm urban areato the right in pink.

By the end of the last ice age about 11,000 years ago, much of northern Europe and North America was covered byice sheetsup to 3 km (1.9 mi) thick. At the end of the ice age when the glaciers retreated, the removal of the weight from the depressed land led to apost-glacial rebound.Initially the rebound was rapid, proceeding at about 7.5 cm (2.95 in) per year. This phase lasted for about 2,000 years, and took place as the ice was being unloaded. Once deglaciation was complete, uplift slowed to about 2.5 cm (1.0 in) per year, and decreased exponentially after that. Today, typical uplift rates are of the order of 1 cm (0.39 in) per year or less, and studies suggest that rebound will continue for about another 10,000 years. The total uplift from the end of deglaciation can be up to 400 m (1,312 ft).[citation needed]

In theViking Age,Mälaren was still a bay of theBaltic Sea,[7][8]and seagoing vessels could sail up it far into the interior of Sweden.Birkawas conveniently near the trade routes through theSödertälje Canal.Due to the post-glacial rebound, Södertälje canal and the mouth ofRiddarfjärdenbay had become so shallow by about the year 1200 that ships had to unload their cargoes near the entrances, and progressively the bay became a lake.[9]The decline of Birka and the subsequent foundation ofStockholmat the choke point of Riddarfjärden were in part due to the post-glacial rebound changing the topography of the Mälaren basin. The lake's surface currently averages.7 m (2.3 ft) abovesea level.

Mythology

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According toNorse mythologyas contained in the thirteenth-century Icelandic workProse Edda,the lake was created by the goddessGefjonwhen she trickedGylfi,the Swedish king ofGylfaginning.Gylfi promised Gefjon as much land as four oxen could plough in a day and a night, but she used oxen from the land of the giants, and moreover uprooted the land and dragged it into the sea, where it became the island ofZealand.Snorra Eddasays that "the inlets in the lake correspond to the headlands in Zealand";[10]since modern maps show this to be more true of LakeVänern,the myth has been suggested to have been originally about Vänern, not Mälaren.[11]

Geography

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A selection, in Alpha betical order:

Major islands Major sections from west to east Major cities and municipalities bordering the lake

Ecology

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The most commonnestingbirds on the skerries of Mälaren are also the most common in the Baltic Sea. After a survey in 2005, the ten most common species were found to becommon tern,herring gull,black-headed gull,common gull,mallard,tufted duck,Canada goose,common goldeneye,lesser black-backed gullandcommon sandpiper.White-tailed eagle,greylag goose,barnacle goose,black-throated diver,red-breasted merganserandgadwallare less common, and some of these latter are endangered in the Mälaren area. Since 1994 a subspecies ofgreat cormorantPhalacrocorax carbo sinensis,has nested there as well. A 2005 survey tallied 23 breeding colonies with 2178 nests, of which the largest colony had 235 nests. Most experts believe the great cormorant population has peaked and will stabilize at around 2000 nests.[12]

One of the characteristic species is theospreywhich has one of its strongest presences in Lake Mälaren. The osprey nests in almost all bays of the lake.[12]

TheZebra musselis considered aninvasive speciesand is causing some problems in Lake Mälaren.

Lake Mälaren has 33 species of naturally occurring fish species, which makes it Sweden’s most diverse lake in regard to fish. Other species have been introduced to the environment, including the common carp and the rainbow trout. The rainbow trout in particular is known to compete with indigenous fish for habitat and food, as they have a faster growth rate and predate on local species. However, they are not considered to have made a significant impact.[13]

Crayfish

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Crayfish are of large cultural and economic importance in Sweden, withcrayfish partiesbeing a longtime annual tradition for many Swedes.

Lake Mälaren was the first lake in Sweden to be affected by thecrayfish plague(A. astaciSchicora)when infected crayfish imported from Finland were introduced to the lake with the intention of human consumption. The plague spread quickly through the lake, exacerbated by boat traffic, which decimated the indigenousnoble crayfish(A. astacus) population and caused severe economic losses to the local fishing industry. From Mälaren, the plague spread rapidly to all freshwater bodies in Sweden.

After multiple recurrent outbreaks and failed attempts to restore populations of the noble crayfish, Swedish authorities introduced the North Americansignal crayfish(P. leniusculus)to L. Mälaren, a species that is resistant to the plague. Since 1969, Mälaren has been continuously stocked with signal crayfish.[13]However, it was later discovered that signal crayfish were often carriers of crayfish plague. In addition, while populations of noble crayfish and signal crayfish have been known coexist, their larger size, faster growth rate, and aggressiveness often allows them to dominate populations of noble crayfish. This, in addition to habitat degradation,[14]has led to a significant decrease in noble crayfish populations in L. Mälaren.

Signal crayfish have been largely successful in Sweden and rapidly expanded as a replacement population to noble crayfish. Stocking this species is now prohibited within multiple lakes in Sweden in order to protect noble crayfish population. In the Stockholm municipality, which includes L. Mälaren, signal crayfish are now illegal to import, move, or farm.[15]There have been efforts to encourage farming of noble crayfish populations instead.[16]However, illegal farming of signal crayfish continues to be a problem due to greater public demand for the larger signal crayfish.[17]

Mapping

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From the mid 17th century onwards, multiple expeditions to measure and map L. Mälaren were undertaken. The lake was strategically and economically important, and there was a lack of a reliable map to navigate it. However, L. Mälaren’s many islands and bays made it an extensive and laborious task to measure.

In 1687,King Charles XI of Swedencommissioned cartographerCarl Gripenhielmto map Lake Mälaren and its surrounding provinces.[18]From 2 August 1688 to 17 September 1688 Gripenhielm conducted the bulk of his expedition, and he would complete the map in 1689, known in Swedish asGripenhielm'sMälarkarta.The Mälarkarta is unique in that it is surrounded by a frame of 96 small, realistic gouache paintings of cities, castles, mansions, and fairways around Lake Mälaren. The map is hand drawn on regal paper, and measures 3.46 m × 2.14 m (11.4 ft × 7.0 ft). It has been kept in theNational Library of Swedensince 1884. Due to its larger size, it was initially hung in the large viewing room, however in 1931 it was moved to a more secluded wall in a corridor to the map department. Heavy handed preservation techniques have led to some degradation on the illustrations. Since 1961, the map hangs in an area that the public does not have access to.

Gripenheim’s Mälarkarta was valid until 1739 when a new, more accurate map of L. Mälaren was completed by the then surveyor and cartographerJacob Nordencreutz.

Trivia

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See also

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References

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  1. ^"Mälaren".The American Heritage Dictionary of the English Language(5th ed.). HarperCollins.RetrievedApril 14,2019.
  2. ^"Mälaren"(US) and"Mälaren".Oxford DictionariesUK English Dictionary.Oxford University Press.[permanent dead link][dead link]
  3. ^"Mälaren".Merriam-Webster Dictionary.Merriam-Webster.RetrievedApril 14,2019.
  4. ^Jöran Sahlgren; Gösta Bergman (1979).Svenska ortnamn med uttalsuppgifter(in Swedish). p. 17.Archivedfrom the original on 2021-01-28.Retrieved2023-12-26.
  5. ^"MälarenArchived2018-06-19 at theWayback Machine".Nationalencyklopedin. Accessed 4 November 2016.
  6. ^Grimes, Heilan Yvette. The Norse Myths. P.285, 286
  7. ^"Landhöjning och bebyggelse i nordligaste Uppland"(PDF).Archived fromthe original(PDF)on 2017-10-20.Retrieved2017-10-09.
  8. ^Friman, Helena,Söderström, Göran.(2008). Stockholm: en historia i kartor och bilder.
  9. ^"Om Mälaren".Archivedfrom the original on 2022-03-28.Retrieved2017-10-09.
  10. ^Anthony Faulkes (ed. and trans),Snorri Sturluson: Edda(London: Everyman, 1987), p. 7.
  11. ^Heimir Pálsson, 'Tertium vero datur: A study of the text of DG 11 4to', p. 44http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-126249Archived2019-09-11 at theWayback Machine.
  12. ^abLänsstyrelsen i Stockholms länArchived2007-09-28 at theWayback Machine- Rapport 2006:02: Mälarens Fåglar (pdf, in Swedish)
  13. ^abJosefsson, M.; Andersson, B. (December 2001)."The environmental consequences of alien species in the Swedish lakes Mälaren, Hjälmaren, Vänern and Vättern".Ambio.30(8): 514–521.doi:10.1579/0044-7447-30.8.514.ISSN0044-7447.PMID11878025.S2CID2171081.Archivedfrom the original on 2022-10-13.Retrieved2022-10-13.
  14. ^Capinha, César; Larson, Eric R.; Tricarico, Elena; Olden, Julian D.; Gherardi, Francesca (August 2013)."Effects of climate change, invasive species, and disease on the distribution of native European crayfishes".Conservation Biology.27(4): 731–740.doi:10.1111/cobi.12043.ISSN1523-1739.PMID23531056.S2CID25775481.Archivedfrom the original on 2022-10-13.Retrieved2022-10-13.
  15. ^"Kräftfiske - Stockholms stad".parker.stockholm(in Swedish). Archived fromthe originalon 2022-10-13.Retrieved2022-10-13.
  16. ^"Noble Crayfish farming in Sweden".SLU.SE.Archivedfrom the original on 2022-10-13.Retrieved2022-10-13.
  17. ^Bohman, P.; Degerman, E.; Edsman, L.; Sers, B. (2011)."Exponential increase of signal crayfish in running waters in Sweden – due to illegal introductions?".Knowledge and Management of Aquatic Ecosystems(401): 23.doi:10.1051/kmae/2011040.ISSN1961-9502.Archivedfrom the original on 2022-10-13.Retrieved2022-10-13.
  18. ^Landell, Nils-Erik (1992).Stockholmskartor.[Stockholm]: Rabén & Sjögren.ISBN91-29-61681-6.OCLC165391840.
  19. ^1912 Summer Olympics official report.Archived2008-04-10 at theWayback Machinep. 224.
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