Reykjavik, Iceland - There's a running joke among many of Iceland's glacier guides.

"There's so much meltwater running off the ice," they say, "someone should buy a boat."

After the financial crash of 2008, tourism in the country flourished and is now at a record high.

But the effects of climate change on its landscape are now as visible as selfie sticks in downtown Reykjavik.

It's expected that more than two million tourists will visit the country of 340,000 this year. Many of these visitors will pay hundreds of dollars just to experience a brief period walking on a glacier.

Ice sheets cover roughly 10 percent of the island, and on most days, guided tours can be found snaking up and down their surface.

It's no secret, however, that glaciers around the world are retreating, and Iceland's most popular ones are melting so fast it's creating problems for the guiding companies.

In some areas, it's even becoming more dangerous for tourists.

A few hours east of Reykjavik is Solheimajokull, a glacial tongue that sprouts off the Myrdalsjokull ice cap in the country's south.

It's losing 100 metres of length a year, releasing millions of cubic metres of water in the process.

In the past five years, the local guide companies have been forced to move their car park after meltwater formed a large lagoon.

The water has also restricted their access on to the glacier.

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Melt rates 'through the roof'

Dieter Van Holder has spent three years working as a glacier and trekking leader for the Icelandic Mountain Guides. He's watched the lagoon grow at an exponential rate.

We have to constantly reinvent ourselves all the time. Dieter Van Holder, glacier guide

"Last year we lost close to 20m of altitude in surface ice," he says.

"This has been going on for several years, but since 2010 the melt rates have gone through the roof.

"We have to constantly reinvent ourselves all the time. We have a lot more work getting on to the ice and maintaining a trail. Personally, I'm starting to fear we're going to lose the front of the glacier to the lagoon.

"This is quite dramatic, not just for us, but for the many companies operating here."

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Getting on a glacier is not as simple as walking straight on to the ice.

Glaciers are dynamic and behave like a thick, slowly moving viscous fluid.

As they shift, their surface undulates and fractures, forcing guides to find new routes - every few days for smaller paths, every week or so for larger ones - where hundreds of people can safely pass with ease.

But finding such a path can be difficult, and with climate change speeding up melt rates, maintaining it for daily use is tiring work.

"I'm managing a couple of guides today," Van Holder says. "My main objective is to free up enough of them to go chopping on the ice so we have a route that's usable.

"We cut into the ice to make a path of stairs, rather than people scrambling and falling over trying to get over uneven parts."

He says the stairs are usually cut into the front of the glacier so people can get on to the ice.

But it's getting harder to do that.

"We used to just walk on to it from the front, but because the lagoon has been growing so fast, we've been pushed into this one corner which is the gnarliest bit of the glacier."

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Dangers for tourists: Falling boulders

The guides used to lead tourists along the side, but big rocks have been falling there recently, making the route too dangerous to use, Van Holder says.

"If you look up the slope, there are massive boulders embedded in ice that's still clinging to the walls. As it melts away, the boulders just drop out and fall to the floor," he says, gesturing with his arms to show how huge they are.

But the tourists don't notice them, Van Holder adds.

"They just see rocks on the ground and think it's OK to walk around them."

Moments later, he dashes to the edge of the glacier. Two American tourists are posing for pictures, unaware that 50 metres above their heads are boulders the size of small cars.

"This is the closest glacier to Reykjavik," says Van Holder, catching his breath, after telling the tourists to move away.

Although the guides have roped off dangerous areas and put up signs, tourists often ignore them.

"For everyone taking a day tour to go on a glacier, most of them come here, so this is a milking cow for many companies.

"When the access here goes, I don't know what most of them will do. Right now a lot of companies are relying on us and [tour operator] Arctic Adventures to keep it accessible."

The planned routes are essential in keeping tourists away from loose ice and hidden crevasses.

They require almost daily maintenance, as what the tour groups don't wear down the sun is quickly melting away, and Solheimajokull has been shrinking since the 1990s.

Glaciologists estimate Iceland's glaciers have been losing about 10km3 of ice every year since 1995.

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A glacier 'changing every few days'

Guides who have been away from the glacier for a few days say they are always shocked by just how much has disappeared when they return.

"Pretty soon, we're going to need to find new places to take the tours on trips," Van Holder says.

"Some time this year or next, I would almost be tempted to put my money on it being inaccessible."

Two hours drive east is Falljokull, a glaciar tongue on the southwest corner of Vatnajokull, Iceland's largest ice sheet, and the second biggest in Europe.

Falljokull is hugely popular with tourists venturing beyond the Golden Circle, a popular tourist route, but worryingly, all its glaciers are shrinking.

From where 4x4 buses drop off tour groups, it's a 30-minute walk across glacial rivers, unsorted debris, and piles of volcanic ash to the edge of the ice.

The water that you see running down off the top acts like a hot knife through butter. Thomas Gruber, Glacier Guides

Halfway, a Nissan Pathfinder is parked just above a recently formed stream. Two guides are hastily building a makeshift bridge over the muddy water.

There is no way to reach the glacier without crossing.

"Some of our guides are building new bridges," says Thomas Gruber of Glacier Guides.

"In the last heavy run-off the old ones were washed away. We have to build them in anticipation of the increased melt run-off in summer.

"This glacier is now in full retreat and we're losing about 14cm of ice a day. Right now it's changing every few days. It's quite amazing how much goes in a short period of time."

Scientists have measured the rate of ice change on Falljokull since 1932.

The British Geological Survey and the Icelandic Meteorological Office found that since 2005, it has been losing more than 35 metres a year as a result of a decade of unusually warm summers.

The glacier's melting ice only contributes to its own erosion, making it harder to explore its hidden features.

"The water that you see running down off the top acts like a hot knife through butter," Thomas adds.

"It cuts its way into the ice, creating more cracks where water can flow and continue melting away on the inside.

"This also has an effect on the ice caves and can flood them with water, making them inaccessible to tours until it drains away. The part of the glacier we are standing on right now will be gone in four to six years," he says.

"If anyone has any job offers, that would be great," he jokes. "It's a bit doom and gloom thinking ahead."

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Tourism boom

When the Eyjafjallajokull volcano erupted in 2010, large areas of the glaciers were covered in a thick blanket of black ash.

That year, melt rates accelerated well above average, in turn speeding the growth of the lagoons.

Despite the eruption, it was Iceland's tourism sector that really exploded. Local patrons of pubs will tell you how the prolonged volcanic eruption actually helped to promote Iceland and attracted visitors to its otherworldly landscape. Many locals complain about the sheer number of tourists.

Even so, a sixth of Iceland's jobs are now in the tourism industry.

Every year, tourists from all over the world bring in billions of dollars in revenue, and have helped to grow its economy to become 10 percent larger than before the crash.

A recent report by the Organisation for Economic Co-operation and Development, a group of 35 mostly rich countries, states that 80 percent of tourists visit for the country's unique "Icelandic nature".

But nothing lasts for ever, and Icelanders understand this all too well.

Like their economy, they know they will have to adapt to a changing climate.

And as the joke goes: someone should buy a boat.

Boats instead of hikes

Bjorn Hroarsson, a geologist and founder of the Extreme Iceland tour company, already has plans in the works.

He started running tours in 1990 and has been forced to make hard decisions in the past.

Now he wants to take advantage of the changing conditions and improve tourist safety by dropping the hiking part of the trips in favour of ferrying people over the water.

"The Solheimajokull glacier lagoon is giving us difficulties," he says.

"It's a longer and longer distance from the car park every year, so a longer hike. The solution will be a boat over the lagoon."

He says they plan to start transferring people to the glacier by boat next summer.

"It'll be much more easy and safe, and take much less time than the current hike."

It's not entirely a new practice; Bjorn says they've successfully used boats in the past.

But the retreating ice could still cause more problems in the future.

The glacier must still be suitable for planning routes on, and that's a factor no tour company can guarantee.

"We were operating day glacier hiking tours from Reykjavik on the Hvítarvatn glacier lake," he adds.

"We used boats on the lake to transfer our guests to the glacier."

But the glacier got shorter and more steep and less safe every year, until they were forced to stop the tours altogether three years ago, Hroarsson says.

The glaciers won't disappear, yet

Iceland's tourism industry continues to grow strong, and seeks to mitigate the problems that climate change is causing to its landscape.

As tour guides spend their days managing routes, the companies are working to adapt for a warming climate with less access to the glaciers.

In Reykjavik there are talks of kayak tours, and even discussions about making helicopter drop-offs more commonplace.

Both options still present their own logistical and financial constraints.

Another issue of concern is the recovery and increased strength of the Icelandic krona since the financial crash, which has led to Iceland becoming one of Europe's most expensive countries to visit, in turn making paid tours less affordable.

But away from the visitor hot spots, the ice sheets are still vast, and Iceland can take solace in knowing it will have glaciers safe for tourists to walk on for some time yet.

"At least no problem at all - for the next few hundred years," Bjorn says.