A British cyclist, who has been biking the length of six continents for the past five years, tackles a daring – and freezing – route in northern Mongolia.

The most disturbing part of walking over Lake Khövsgöl in northern Mongolia wasn’t the sound of cracking ice. It was the thuds.

The thuds meant that water was on the move, bubbling up through fresh rifts in the metre-thick ice that lay under my boots, three pairs of socks and numb feet.

My hope was to cross the frozen lake by bicycle and camp out on its surface – although the soundtrack was highlighting some icy holes in my plan. This was the latest in a series of two-wheeled adventures, having spent the last five years cycling across six of the Earth's continents.

At first glance, Lake Khövsgöl – the sprawling home to 70% of Mongolia’s freshwater (and a full 1% of the planet’s stash) – was mesmorising. Measuring 136km long and up to 35km wide, the blue-green lake lies at the base of the permanently snow-capped Sayan mountains, an extension of the bolder Altai range that trails into Central Asia.

What drew my eyes most was the intricacy of the ice itself. I lay down on my belly to get a better look, peering into a web of silvered fissures, like reams of tinfoil suspended in glass. Inside the ice were solar systems of snow and vertical trails of one-time escaping air bubbles impounded by the winter chill. It was impossible not to wonder what might twitch and jink beneath the ice, but the water was eerily still.

I strolled a couple of kilometres back to the small town of Khatgal where I was staying in one of the tourist gers on the lake’s southern shore. A local guide, Ganbat, and I sat hunched over a rumpled map from Mongolia’s Soviet years, when Russian oil would be taken across the lake by ship in the summer and by truck when the ice was thick enough. Siberia lies just 20km from the lake’s northern shore.

Summer is the time most travellers come to Khövsgöl, to ramble, splash, paddle or gallop about. But I was here in March, meaning it was dry, sunny and cold enough to marvel at the ice that seals the lake from December to June. During this time of year, the nightly temperature dips to the un-Spring-like depths of -20C (still toasty compared to the -40C bite of mid-winter), and the ice can bear the weight of cars and trucks – as well as bikes. If you smashed a hole in it – like the ice fisherman do every day on the fringes, or like Russian tourists do before launching their vodka-fuelled bodies into the water – the ice would begin to re-accumulate at 5cm a day.

An estimated 40 trucks have fallen through the ice over the years, and in the early 1990s – at around the same time that Khövsgöl was incorporated into a national park – authorities banned heavy vehicles and the transportation of oil over the lake to prevent further pollution. Some sunken trucks were extricated by the military; divers have since found others, their gallons of oil resting on the lakebed. Ganbat pointed absently to the spot where, two years ago, he’d lifted a bunch of Russians from the roof of their car as it slipped underwater on sinking fragments of ice. “City types”, he said with a wry smile, “they don’t know the weak points.”

Forewarned about weak points (they form around spits of land and river mouths), and with studded tyres in situ, I returned to the lake with my bike, passing the harbour containing two aging ice-packed ships. Since various local industries were shut down, the area has become a celebrated wilderness, with tourism growing appropriately year on year. As if in declaration of this shift, a Jeep carrying a few Mongolian tourists careened over the ice in front of the derelict ships, and I pedalled off from the southern shore.

My plan was to ride north over the ice, staying close to the eastern shoreline until the lake became wider, and then to cross from the east to the west, where I would camp out on the ice.  There were some bumps in the ice, but my tyres held firm and soon I was skittering along, tailwind assisted, grinning madly and indulging in the matchless joy of riding without a road to follow. In the distance, the remaining ice sculptures – eagles and mermaids from the annual March Ice Festival – glittered under Mongolia’s stubbornly blue sky.

The bite of my studded tyres kept me vertical early in the day when the temperature remained below zero, but in hindsight, only a Fat Bike (the monster-truck of the bike world) with much chunkier tyres would have coped in the warmer afternoon, as a film of invisible water layered the ice and I was soon sent sliding about, tumbling twice.

Luckily, beyond the western shore of the lake, a good trail runs through larch forest. So I changed my plan, retreated from the ice and pedalled over a bed of fallen needles, hoping to catch a glimpse of wolves, moose or wild sheep. Khövsgöl is within the realm of the taiga – the vast boreal forest that encircles the Earth in these northern latitudes.

By the evening, I’d covered 60km of ice, trail and more ice, cycling a quarter of Lake Khövsgöl’s length, as well as crossing from the eastern side to the west. The ice had warmed now, grown cantankerous. The most soul-chilling snaps came from towards the lake’s centre, and were chased by thuds as though the ice had a heartbeat to rival my own.

Dusk upset the colour scheme: the ice soured to almost black, the snow turned a glacial blue. I set up my tent on the most fetching, limpid ice, shuffled over its quivering reflection, and climbed inside.

A Mongolian boy, festooned in a fox fur hat and woolly wine-toned deel (traditional robe), had spotted my tent from his nearby ger and abandoned his horses and yaks to investigate. My less-than-pidgin Mongolian quickly turned to mime: “riding bicycle”, “sleeping here”, “beautiful”.

“It is,” he nodded. Lake Khövsgöl, with its ever-evolving cracks and freeze-thaw and shifting hues through day, month and season, could be a metaphor for the mutability of life in Mongolia, a country strewn with one of largest nomadic populations on Earth.

I slept well, ensconced in three sleeping bags, lulled by the thuds, gurgles and cracks. I woke to a gold band seaming the taiga to a royal blue sky and thought about those oil trucks languishing in the deep, about the all too common marriage of fragility and beauty in the wild.

Before I packed up camp and cycled back to Khatgal, I snapped a few photos of the sunrise, pitching some creative curses to the wind. To use my camera I had to remove my gloves; the temperature was still -20C and my hands were approaching the colour of Mongolian ice.

Where do you rank in our tribe of worldly readers? Answer these questions to get a sense.