Sólheimajökull

Sólheimajökull is an outlet glacier, 11 kilometres long and one to two kilometres wide, flowing from the south-western part of the ice cap above it. It starts at about 1,350 metres above sea level and runs down a valley to its snout. Most of it lies below the line where winter snow outlasts the summer melt, so it survives on ice pushed down from higher up.

That makes it quick to react to the climate. Between 1930 and 1969 the snout pulled back about 977 metres. A colder spell then pushed it forward about 495 metres by 1995, and the ice grew about 100 metres thicker. Since then it has been retreating again. By 2010 the snout stood about a kilometre further up the valley than in 1930, and the ice was 120 to 150 metres thinner than in 1960. If the retreat goes on, it could disappear completely within the next 100 to 200 years.

The lagoon in front of the glacier is already 60 metres deep and could grow to four kilometres long in the coming decades if the retreat continues. Students from a local school take GPS readings of the snout every year to track the change. The glacier lies inside a UNESCO Global Geopark.

A hike begins on foot from the car park, along a marked trail towards the ice. Before stepping on to the glacier, your guide fits you with crampons and a helmet, usually with a harness and an ice axe, and shows you how to walk in them. Most of the time is spent moving slowly over uneven ice while the guide picks a safe line.

Icelandic glaciers are temperate, meaning the ice sits at melting point and water runs through and under it. Cracks called crevasses open in the top 20 to 30 metres of ice as the glacier moves over uneven ground. Near the snout, rock debris and volcanic ash gather in thick black bands, which is why the lower glacier looks streaked with grey and black rather than clean white.

The edge of the glacier changes quickly. A second lagoon has formed beside the tongue, the ice ridge once used to reach the glacier has thinned, and rocks can fall from the slopes of Jökulhaus above the south-eastern approach. Guides adjust the route as the ice moves, and they will change or cancel a hike on the day if it is not safe.

Wear layers, with wool or synthetic fabrics rather than cotton, a wind- and waterproof outer shell, gloves and a warm hat. Sturdy waterproof boots are needed for crampons; some operators lend or rent them, so check each card.

With Sólheimajökull, the conditions on the day count for more than the month. Glaciers move faster in summer, when more meltwater runs beneath the ice, and the surface and the approach can look different from one week to the next.

Iceland's weather can turn quickly, and on a glacier it can be harsher than in other remote areas. Wind, rain and cold together are easy to underestimate, and hypothermia is a real risk even in summer, so dress for worse weather than the forecast.

If you are touring the south coast, a glacier hike fits well into a day that also takes in Skógafoss to the west and the black-sand beaches near Vík to the east. Book a time that leaves room for the drive and the walk from the car park.