Greenland is melting so fast at the moment, climate scientists are finding it hard to keep up. Predictions and models need to be rewritten to take into account events happening way ahead of schedule, and the logistics of getting around have to shift when the ice you travel on turns to water. Dr Steffen Olsen of the Danish Meteorological Institute summed up the second problem with this photo of a sled team running through water as far as the eye can see.

Parts of Greenland melt every summer. Most freeze again in winter, but in recent years the ice budget has stopped balancing. This year, melt rates are like nothing previously seen in June and far above the normal peak. The cause is a combination of long-term warming and a high-pressure system that led to temperatures spiking. No one really knows how long this will continue and just how much of Greenland will be lost, but we do know this is not normal and much of the former ice will raise sea levels worldwide.

In May, climate scientists noticed Greenland was exceptionally warm, even by the hotter standards of recent years, and predicted rapid melting.

We're a month off the usual peak, and already Greenland's melt rate has exceeded the top 10 percent of years since measurements existed. National Snow and Ice Data Center.

Olsen is one of the scientists trying to get a handle on what is happening. Each year, he places monitoring equipment on the sea ice at Inglefield Bredning, northwest Greenland, collecting it before the melt sets in. This year, the melt arrived long before schedule, but the ice below was solid enough that the water couldn't drain away through cracks.

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One photo at one location could be deceiving, but charts like the one above give a better idea of what is going on. As it reveals, melting usually peaks in July, but by the second week of June, melt rates already exceeded normal annual maximums. It's too early to tell if this will be the biggest melt of all time or if it will fall behind the epic 2012 floods, but no other year looks close.

At this point, almost half of Greenland is melting this year.

An estimated 45 percent of Greenland was melting on June 15. National Snow and Ice Data Center

The day Olssen took this photo, it is estimated Greenland lost 2 billion tonnes of ice. That's almost enough to cover the whole of Great Britain in 1 centimeter (0.4 inches) of ice.

Lest you think this is just a localized issue to one (very large) island, things are actually much worse sixty degrees further west. So far this year, it is Alaska and the sea to the north that have really been getting a taste of the future.

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In the 19th Century, sea ice north of Alaska was so thick that thousands died seeing the North-West Passage. Now, there is less than 15 percent ice for most of the way.

Since water is darker than ice, a layer like the one Olssen's dogs are splashing through prevents the 24-hour sunlight from being reflected, creating more warming and a vicious circle.