{"id":179,"date":"2017-09-17T17:29:53","date_gmt":"2017-09-17T17:29:53","guid":{"rendered":"http:\/\/80.85.86.254\/sjor\/?p=179"},"modified":"2025-06-11T17:18:22","modified_gmt":"2025-06-11T17:18:22","slug":"1-4-sjavarstraumar","status":"publish","type":"post","link":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/2017\/09\/17\/1-4-sjavarstraumar\/","title":{"rendered":"1.4 Sj\u00e1varstraumar"},"content":{"rendered":"

Vatnsmassi sj\u00e1var er \u00ed st\u00f6\u00f0ugri hringr\u00e1s sem kn\u00fain er \u00e1fram af sj\u00e1varstraumum. S\u00f3lin og m\u00e1ninn hafa \u00e1hrif \u00e1 sj\u00e1varfallastrauma vi\u00f0 str\u00f6ndina. Vi\u00f0 yfirbor\u00f0 sj\u00e1var eru straumar a\u00f0 mestu drifnir \u00e1fram af vindum. A\u00f0rir og mun h\u00e6gari straumar fr\u00e1 yfirbor\u00f0i sj\u00e1var a\u00f0 sj\u00e1varbotni eru hins vegar drifnir \u00e1fram af breytingum \u00ed hitastigi og seltu sj\u00e1var, \u00ed ferli sem kallast hita-seltu-hringr\u00e1sin. \u00deessir straumar flytjast \u00e1 st\u00f3ru \u201ealheimsf\u00e6ribandi\u201c og er Atlantshafsveltihringr\u00e1sin (AMOC<\/span>) hluti af \u00feessu f\u00e6ribandi.<\/p>\n

Loft- og hafstraumar vinna saman a\u00f0 \u00fev\u00ed a\u00f0 dreifa \u00feeirri s\u00f3larorku sem berst til jar\u00f0ar. Loftstraumarnir eru kn\u00fa\u00f0ir af hitabreytingum \u00e1 yfirbor\u00f0i jar\u00f0ar og vindakerfum. Vindarnir toga \u00ed yfirbor\u00f0ssj\u00f3 og koma af sta\u00f0 vindstraumum. Sn\u00faningur jar\u00f0ar hefur \u00e1hrif \u00e1 stefnu straumanna og \u00fea\u00f0 gerir einnig d\u00fdpi og l\u00f6gun sj\u00e1varbotnsins. Upphitun e\u00f0a k\u00e6ling \u00e1 yfirbor\u00f0ssj\u00f3 og seltubreytingar vegna uppgufunar e\u00f0a \u00farkomu, breyta e\u00f0lis\u00feyngd sj\u00e1var og e\u00f0lis\u00feyngdardreifing kemur af sta\u00f0 straumum. Vi\u00f0 sj\u00e1varyfirbor\u00f0 eru straumar sem fyrr segir a\u00f0 mestu drifnir \u00e1fram af vindum. \u00c1 meira d\u00fdpi r\u00e1\u00f0ast straumar af e\u00f0lis\u00feyngd sj\u00e1var, sem aftur er h\u00e1\u00f0 hitastigi og seltu. Dj\u00fapsj\u00e1varmyndun \u00e1 s\u00e9r n\u00e6r eing\u00f6ngu sta\u00f0 \u00e1 k\u00f6ldum hafsv\u00e6\u00f0um. V\u00ed\u00f0ast \u00e1 nor\u00f0l\u00e6gari breiddargr\u00e1\u00f0um er \u00farkoma meiri en uppgufun og \u00fea\u00f0 kemur \u00ed veg fyrir a\u00f0 bl\u00f6ndun geti \u00e1tt s\u00e9r sta\u00f0 ni\u00f0ur \u00e1 miki\u00f0 d\u00fdpi. Af \u00feessum \u00e1st\u00e6\u00f0um getur dj\u00fapsj\u00f3r a\u00f0eins myndast \u00ed tveimur tilvikum: ef seltur\u00edkur sj\u00f3r berst til \u00edshafssv\u00e6\u00f0anna og k\u00f3lnar \u00fear; e\u00f0a ef tilt\u00f6lulega seltur\u00edkur sj\u00f3r fr\u00fds. Dj\u00fapsj\u00e1varmyndunin ver\u00f0ur einkum \u00e1 tveimur sv\u00e6\u00f0um, vi\u00f0 Su\u00f0urskautslandi\u00f0 og \u00ed Nor\u00f0ur-Atlantshafi. Tilt\u00f6lulega saltur hl\u00fdsj\u00f3r fl\u00e6\u00f0ir nor\u00f0ur um Nor\u00f0ur-Atlantshaf og mi\u00f0lar varma til andr\u00famsloftsins. Vi\u00f0 \u00fea\u00f0 k\u00f3lnar hann og k\u00e6lingin eykur e\u00f0lismassa \u00feessa sj\u00e1var svo a\u00f0 hann sekkur a\u00f0 lokum og myndar dj\u00fapsj\u00f3, einkum \u00ed Nor\u00f0ur-Gr\u00e6nlandshafi (milli Jan Mayen og Svalbar\u00f0a) og \u00ed Labradorhafi (milli Gr\u00e6nlands og Labrador). Dj\u00fapsj\u00f3rinn fer\u00f0ast svo su\u00f0ur me\u00f0 botni Atlantshafsins og dreifir s\u00e9r b\u00e6\u00f0i um Indlandshaf og Kyrrahaf \u00fear sem hann kemur upp \u00e1 yfirbor\u00f0, hitnar og flyst sem hl\u00fdsj\u00f3r aftur \u00ed \u00e1tt a\u00f0 Atlantshafi. \u00deetta ferli kallast hita-seltu-hringr\u00e1s.<\/p>\n

Sterkir straumar eru \u00ed \u00f6llum heimsh\u00f6funum og \u00feess vegna flyst st\u00f6\u00f0ugt miki\u00f0 magn sj\u00e1var um \u00fe\u00fasundir k\u00edl\u00f3metra. Hafstraumar, s\u00e9r \u00ed lagi styrkur \u00feeirra, breytast oft me\u00f0 \u00e1rst\u00ed\u00f0um og ve\u00f0urfarssveiflum. Sj\u00e1 m\u00e1 hreyfimynd af hafstraumakerfi heimshafanna \u00e1 myndbandi 1.3.<\/p>\n