A female British adventurer is preparing for the final leg of her gruelling challenge to circumnavigate the world using just human power - four years after she set off. Sarah Outen MBE, 29, has already travelled a staggering 20,500 miles since she left Tower Bridge in London in a kayak on April 1, 2011. The Oxford graduate paddled from Britain to France and cycled 11,000 miles across Europe before jumping back in her kayak to travel from Russia to Japan. Scroll down for video . Sarah Outen, pictured after arriving in New York by bike from Alaska, is preparing for the final leg of her gruelling challenge to circumnavigate the world using just human power - four years after she set off . Sarah  has already travelled a staggering 20,500 miles since she left Tower Bridge in London in a kayak on April 1, 2011 . She then set off to row across the Pacific Ocean to Alaska but had to be rescued after her boat was battered by 80mph winds in a three-day tropical storm. She said she strapped herself to the bunk of her rowing boat while she waited for help. She said: 'That was really scary, it was a really intense few days being in those conditions and being alone. 'The water was coming in and there was nothing I could do but wait so I lay on my bunk strapped in and floated for three days. The Oxford graduate paddled from Britain to France and cycled 11,000 miles across Europe before jumping back in her kayak to travel from Russia to Japan . Love boat: Miss Outen proposed to her girlfriend Lucy from the middle of the sea using a satellite phone . The adventurer has 3,000 miles left to go before she completes her trip . A moment of respite: Sarah setting up camp at Shalti lake, in China, in June 2011 . Sarah in a sunbaked Gobi desert during her 11,000-mile ride to the edge of Russia . The route Sarah has taken since leaving London in 2011, with the final leg a row across the Atlantic . April 2011 - Sets off from Tower Bridge in London. Kayaks from London to France, then cycles 11,000 miles across Europe and Asia before kayaking from Russia to Japan. May 2012 - Rows across the Pacific Ocean to Alaska but is rescued by Japanese coastguards a month into the five month journey. She goes home to recover for nine months where she meets her fiancee Lucy. April 2013 - Returns to Japan and rows across the Pacific Ocean to Alaska, arriving in September 2013. Proposes to Lucy via satellite phone from middle of Pacific Ocean. Returns home because of Alaskan winter. May 2014 - Returns to Alaska and kayaks 1,500 miles along the Aleutian Islands. Has just a two week break before cycling 4,500 miles through Alaska, Canada and the United States in one of the harshest winters the country has seen. March 2015 - Arrives in New York. Plans to stay for two weeks before cycling 400 miles to Cape Cod and then rowing solo for 3,000 miles across the Atlantic Ocean back to the UK. She will then cycle, kayak and row back to Tower Bridge aiming to arrive in September . 'I zoned out as much as I could and there was just one occasion when I lost it and started crying. 'The Japanese coastguard plane was flying overhead and I had to go out to let off a flare so they could find my position. 'I wasn't strapped in and a wave hit and I got thrown around the cabin and I was exhausted and scared so just burst into tears. 'But I told myself to pull it together and luckily got rescued.' The physically demanding journey has also been an emotional one for Sarah who proposed to partner Lucy Allen, 28, whilst she was in the middle of the Pacific Ocean. She said: 'I met Lucy during the time at home so in a way I was lucky that I capsized and was forced to abandon that row to Alaska the first time. 'We had talked about getting married and said we would propose to each other when I reached Alaska. 'But I was alone in the middle of the Pacific Ocean and I thought why wait so I picked up the satellite phone and just went for it. 'I had to ask her twice because she couldn't hear me properly but she said yes.' She returned to Japan in April 2013 and completed the five-month journey which made her the first and youngest person to row solo from Japan to the Aleutian Islands. Incredibly, she then kayaked 1,500 miles along the Aleutian Islands with pal Justine Curgenven before cycling 4,500 miles through Alaska, Canada and the United States. Since then she has battled plunging -40C temperatures and narrowly avoided being attacked by grizzly bears. Sarah, from Oakham, Rutland, eventually arrived in New York last Thursday and is having a two-week break until she cycles another 400 miles to Cape Cod. She will then prepare to row Happy Socks for the final leg of her journey, a solo trip across 3,000 miles of the Atlantic Ocean back to the UK. She said the most testing part of her incredible trip has been camping in plunging temperatures and tackling wild bears along her route. She said: 'It was difficult because overnight the temperature dropped below -40C several times which made breathing in the tent very difficult. 'There were ice particles in the air when I was up in Alaska and northern Canada between August and October. 'Some kind people invited me in to their homes but I mostly camped and I knew bears were around so at night my mind would play tricks on me. 'There was no-one around and the sound of bears in the forest would keep me awake at night. 'I only saw one bear on the bike when a brown grizzly ran across the path I was cycling on and disappeared. 'But during the kayaking along the Aleutian Islands we saw lots of grizzly bears on the banks of the shore. 'One evening I was in a stream having a wash and I suddenly saw this big grizzly bear walking towards me downstream. 'All I could do was get out as quick as I could and luckily my clothes were on the shore so he had a good sniff of them and that slowed him down. 'We were able to make a fuss and throw some stones in the water and luckily that scared him off but he was only a few feet away from us.' Plotting the course for adventure: Sarah plots her route while in the cabin of her boat, Happy Socks . Sarah uses the radio in her boat Happy Socks, which she has used to cross the North Pacific . Peddle power: Sarah has cycled over 15,000 miles during her odyssey. She's pictured here in China . Sarah began her long trip by kayaking from London at Tower Bridge to France in 2011 .
Sarah Outen left Tower Bridge in London in a kayak on April 1, 2011 . She paddled to France then cycled 11,000 miles across Europe . Then she jumped back in her kayak to travel from Russia to Japan . She then rowed across the Pacific Ocean to Alaska in September 2013 . After that she cycled 4,500 miles across North America to New York .