Jokulsarlon literally means glacier lagoon (Jokull - glacier, lon - lagoon). At the time when first settlers arrived in Iceland, the edge of Breidamerkurjokull, an outlet glacier of the great glacier Vatnajokull, is thought to have been 20km further north than it is now. The climate began to cool in about the year 1200, the cold spell reaching a peak in the period 1600-1900, which is sometimes known as the "Little Ice Age". As a result the glacier advanced until about 1890, reaching a point only about 1km from the coast at Jokulsa river. The eastern part of the glacier eroded the sediments of Breidamerkursandur to a depth of up to 300m below sea level, the sediment being carried forward by the river Jokulsa. Without the river the glacier could not have eroded such a deep basin, because it is the river that carries the sediment to the sea.
The warm period from 1920 to 1965 caused great changes in Breidamerkurjokull glacier. It retreated very quickly, leaving a lagoon up to 190m deep where the glacier snout had been, and several kilometers of glacial moraines were exposed on both sides of the lagoon. The lagoon grew from 8km2 in 1975 to 15km2 in 1998. Large blocks of ice break off the edge of the glacier, which is about 30m high, keeping the lagoon stocked with icebergs.
The white cap of Breidamerkurjokull glacier dominates the lagoon and its icebergs. Jokulsarlon is separated from the sea by only a short distance, and the combined action of the glacier, the river that empties from the lake, and the ocean may eventually transform it into an inlet of the sea. There are plans to prevent this from happening, since the only road in the area passes over the narrow isthmus.
The weather is fairly temperate year round around Jokulsarlon but one should bring a waterproof winter coat and wear waterproof shoes. During the winter it may be cold, windy, and rainy so winter weather clothing is advisable.
Jokulsarlon is on the edge of the National Highway 1 so very accessible if you stop on the side of the road.
As with all natural attractions in Iceland, there is no entrance fee.
Getting around Iceland is rather easy, since there are few roads. Because Jokulsarlon lies along the major ring road it is easily accessed. The two best ways are (1) rent a car from Reykjavik or (2) rely on the highly efficient, very punctual public bus that will happily drop you off for as long as you like. Because car rentals in Iceland tend to be very expensive (well in excess of $150 per day for a compact Suzuki SUV) their public national transit system is outstanding. Buses can be taken virtually anywhere; take one to Jokulsarlon, stay for a few hours, then catch another headed in either direction along the ring road.
Apart from the obvious, marvelling the amazing site, there are also boat trips available. There is a small office next to the lagoon that runs trips into the lagoon and amongst the icebergs from June 15 to September 15.
This no accommodation at the lagoon itself but there are several hostels and other accommodations in the surrounding area. There is also accommodation at Hofn, 60km east.
Jokulsarlon is accessible by car and is located on the Ring Road (Route 1) between Hofn and Skaftafell National Park in Southeastern Iceland. The lagoon is about 50km from Skaftafell (but can take an hour) or 60km from Hofn.
After visiting Jokulsarlon, one can travel to Skaftafell National Park and hike the glaciers.