Around Helagsglaciären there was lots of snow, lots of red snow. It looked bloodstained, which would have been very bizarre and possibly overlooked had I not read about 'Watermelon Snow' before hand.
This incredible phenomenon is caused by a type of algae which is red instead of green and thrives in these cold, alpine environments. It is suggested that the red colouring is an evolutionary trait that protects the algae from the powerful UV rays of the sun, much like sun cream. Although it might look the colour of watermelon, it is not considered edible and may even cause dietary problems if consumed, so add it to your list of snow colours to avoid eating! The algae lays dormant for the winter, whilst it is covered in metres of snow, and only appears, making the snow red, in the late summer, when the snow covering has melted away and the warmth from the sun allow it to get liquid water.
Despite living on snow, these algae still require liquid water. So how do they do it? The algae use an extremely ingenious technique of lowering the albedo (reflectiveness) of the snow so that it absorbs more heat and therefore melts, right where the algae are touching it. This is such an impressive system because it's completely passive. The algae lower the albedo simply because they aren't white, so absorb more energy from the sun. However, this can cause problems in fragile areas where snow is rapidly depleting, like in the arctic, as the snow-algae lower the albedo and speed up the melting.
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