摘自某老外的blog
I"m sorry to ruin the fun of this but that"s a lie. Actually, it"s two lies.
First, the Baltic sea and the North sea are both salt water, and salt water is miscible. Being miscible has nothing to do with density. Two liquids of different densities can mix.
Second, the photo wasn"t taken where it is said it was; it was taken aboard an Alaskan cruise
我很遺憾的掃興了，但是這確實是謊言。事實上是兩個謊言.
首先，波羅地海和北海都是鹽水溶液，鹽水和鹽水之間是互溶的，和密度無關。兩種不同密度的液體可以混合。
其次，這張照片並不是拍自波羅的海和北海，而是拍阿拉斯加的游輪上。
然後是照片原作者的解釋：
I thought I would clarify the image of the Merging Seas, in fact it is my image I posted on Flickr a few years ago and it has gone viral a few times. I call it "Merging Oceans". It was taken on a cruise in Alaska in the Alaskan Gulf, not in the North Baltic sea.
我想我要澄清一下這張並列的海的照片，事實上這是我幾年前在Flicker刊物上發表的文章並且它火了幾次。我取名為「並匯之海」。這種照片攝於阿拉斯加海灣的一艘游輪上，而不是波羅的海和北海。
那麼，這種景觀是如何出現的呢？
以下是參考自Quora和mythbusting的答案：
This is an urban legend. The picture shown is not the Baltic Sea and North Sea, and the border shown is not due to salinity gradient. The picture is from Alaska, showing where dirty glacial meltwater was flowing into the open ocean. It"s a temporary phenomenon caused by sediment washed into the ocean -- microorganisms thrive on the nutrients. The color is not due salinity.
Waters of different salinity levels will mix quite easily when exposed to disturbances from wind, waves, and current. Salinity separation phenomena like haloclines are only stable in low-energy systems like caves or when constantly regenerated by persistent effects like surface evaporation. In either case, the halocline is a horizontal boundary (eg gravity puts the lighter fluid on top), not a vertical line like is shown in the picture.
Ken Bruland, professor of ocean sciences at University of California-Santa Cruz, was on that cruise. In fact, he was the one who snapped the pic. He said the purpose of the cruise was to examine how huge eddies -- slow moving currents -- ranging into the hundreds of kilometers in diameter, swirl out from the Alaska coast into the Gulf of Alaska.
Those eddies often carry with them huge quantities of glacial sediment thanks to rivers like Alaska』s 286-mile-long Copper River, prized for its salmon and originating from the Copper Glacier far inland.
Ken Bruland，加州聖克魯茲分校海洋學教授，在那艘游輪上拍了這張照片。他說那次探查的目的在於研究巨大的漩渦——緩慢移動的洋流，如何擴散數百公里的直徑，進入阿拉斯加海岸。
這些洋流經常攜帶大量的冰川沉積物，這些有鮭魚和庫珀冰川留下的沉積物來自諸如庫珀河之類的河流。
「They do eventually mix, but you do come across these really strong gradients at these specific moments in time,」 he said. Such borders are never static, he added, as they move around and disappear altogether, depending on the level of sediment and the whims of the water.
