Polar explorers Pen Hadow, Ann Daniels and Martin Hartley have completed their epic trek across the Arctic.
They were taking measurements of sea-ice thickness - primarily from drilling following the failure of a mobile radar unit - in a bid to help scientists better understand the changes taking place at the highest latitudes.
The BBC's environment correspondent David Shukman, producer Dominic Hurst and cameraman Tony Fallshaw flew out to meet the team as the gruelling expedition (which began on 28 February) came to an end.
WEDNESDAY 13 MAY - THE BIG DAY
From BBC environment correspondent David Shukman: A flurry of last-minute weather checks (there's apparently a window in the cloud), a rush to make some sandwiches (not my best), and soon we're airborne with two planes on a long haul over the Arctic Ocean.
Two planes are used because the distances are so huge that one aircraft serves as a fuel tanker.
Even the one we're in has a large yellow fuel barrel strapped inside to make sure we have the range to get out to the ice camp and back.
Logistics are everything up here and the planning is intricate.
As we head north, we see our first cracks in the ice, a dark line snaking to the horizon.
An hour later many more appear, great fissures like rivers, criss-crossing the white. When we've flown for nearly three hours, there's what looks like a lake.
The summer break-up has obviously started, which is why the Catlin Arctic Survey was brought to an end a week early.
After three hours' flying, we descend and see three figures, tiny against the expanse of white - Pen Hadow, Ann Daniels and Martin Hartley.
The tanker plane has already landed.
We touch down - the plane is fitted with skis. There's quite a bump.
Soon we all climb out and greet the three explorers.
For a brief moment, we must be the world's most northerly social gathering, chatting on the sea ice as if we'd met in the street rather than swaddled against the cold just 500km from the North Pole.
Their clothes look battered, their faces tired, and they keep apologising for the smell. I try to be polite, but there's no avoiding the fact that they haven't had a proper wash for more than 10 weeks.
They pack up their tent, their sanctuary for all that time, and as the gear is stowed in the planes, I look back at the spot where the expedition ended.
A thin cover of snow rests on a metre of floating ice. Soon the footprints will be erased.
And in a few months, the whole icy landscape will have melted into the ocean.
We fly back together, the aircrew keeping the cabin chilled - they've picked up unwashed explorers before.
The team are in amazingly good spirits - avidly going through messages, suddenly self-conscious about looking grubby, and hungry for anything different from their normal rations: even my sandwiches go down well.
After what they've been through, you'd think they'd rather never see ice again.
But there's one very live topic of conversation: the next one
WEDNESDAY 13 MAY - DAY 75 - THE END IS NIGH
From Pen Hadow: We took what are probably going to be our last steps northwards yesterday.
We set off earlier, not knowing that we would find what turns out to be a perfect ski-way for the pick-up plane to land on.
We'd had indications from the satellite imagery that there was a likely site, but you can never tell until you check it out whether it's going to be totally OK or not.
So here we are, tent pitched and waiting to be taken off.
We've all got pretty mixed feelings.
Great sadness because it's nearly over, and great joy at the thought of getting home to civilisation and seeing friends and family.
The sea-ice areas around us continue to break up, which is about two or three weeks earlier than originally expected.
I hear from our operations team that a couple of the other government-sponsored Arctic expeditions - Danish and Canadian - had to be emergency-evacuated recently.
It seems that we are the last out here, so I guess we can claim to be the first out and last back this year!
From here on in, it's down to the weather and support teams.
We just wait.
Mind you, Martin and I are still getting in some drilling - we may as well get in as much as we can before we leave.
From blizzards to sunshine
Overall, apart from me drilling like a mad thing, the journey has had unbelievable highs and lows.
The Arctic has thrown everything it had at us, from blizzards and brutal cold to glorious sunshine and astonishing landscapes.
We have gone from total lethargy due to lack of food to great energy brought on by the appearance of the sun after many weeks of Arctic winter.
Without pre-empting any scientific results, my general impression is that the sea ice seems to be thinner than expected.
And the fact that it has been predominantly first-year ice means that it's more likely to totally melt this year.
My thanks to Ann and Martin - the teamwork has been extraordinary, and I cannot think of two other people I'd prefer to undertake an expedition with.
My thanks to them both for being great friends, colleagues and unswervingly professional explorers.
Ann has done an extraordinarily good job of navigation and path-finding, and Martin has visually captured our story so well and has been invaluable with the manual drilling work - plus being stoical as the object of our bad jokes on many occasions.
We've all managed to retain our sense of humour through thick and thin - which is, I think, a sign of true friendship.
WEDNESDAY 13 MAY - ONE STEP CLOSER
From BBC environment correspondent David Shukman: We're now very close to the edge of the map, nudging the roof of the world at Eureka Weather Station, a huddle of buildings just 600 miles from the North Pole.
This is the jumping-off point for the flight that will collect explorers Pen Hadow, Ann Daniels and Martin Hartley at the end of their expedition.
All eyes are on the weather.
But since Eureka is the last manned station before the long miles out to the camp on the ice, no-one can be sure how the Arctic elements will behave on the way there.
I was stuck here two years ago waiting for the skies to clear.
It wasn't even a storm that delayed us, just a blustery wind that brought grey clouds, a little snow and a lot of boredom.
Back then, we were trying to land on a newly-formed island of ice the size of Manhattan. Eventually we made it.
Since then, three more ice islands have broken off from the coast, the Arctic has gone through record melting and its geography is being altered with extraordinary speed. But Eureka is delightfully unchanged - the same huge freezer of ice-cream and great platters of cookies - a calorie colony in a land where the cold sharpens appetites.
Earlier, back in Resolute, an Inuit guide took us by ski-mobile onto the frozen ocean.
I'd imagined a smooth ride, but it's surprisingly bumpy, with gnarled ridges and lumps of ice, and the occasional iceberg trapped in place.
We reach the edge of the ice and look out at open water, the start of the summer melt.
The bright ice is strong enough to walk on, the darker stuff is to be avoided because it's too thin, a reminder in a beautiful scene of the Arctic's fragility.
TUESDAY 12 MAY - BBC ARRIVES IN THE ARCTIC
From BBC environment correspondent David Shukman: As we head deeper into the Arctic, the airports become tinier, communications harder and the world much stranger.
Partly it's to do with arriving in a frozen land where there's permanent daylight but few signs of spring.
We're in Resolute Bay, one of humanity's northernmost outposts, and it's still blanketed in white.
This is a part of the planet where it's normal to have huskies howling on their tethers. And outside your house, instead of washing drying on a line there are polar bear skins hanging in the pale sunshine.
But this world also feels strange, and on the last two legs of the journey - from Iqaluit to Resolute Bay - the 20 or so passengers are an extraordinary mix.
Usually it's the travelling BBC News team that's the oddity on remoter voyages. But this time cameraman Tony Fallshaw, producer Dominic Hurst and I are hardly worth a second glance.
It's Tony who notices that four men at the back have their wrists unusually close together: between the folds of their jackets there's the unmistakeable glint of chrome on handcuffs.
The prisoners, charged with serious offences, have been on remand and are now returning to their communities to face trial. The Resolute Bay courthouse will be busy this week.
We joke that this has all the makings of an Arctic thriller: if we have to put down in the snow, the only people who'll know how to cope will be the Inuit prisoners.
A few rows in front sits a lawyer, who, it turns out, will be the prosecutor.
Beside me is a doctor, on a regular visit, who tells me that she often treats victims of violence, and that the rates of murder and suicide are far higher in this distant territory than in any other part of Canada.
Soon our journey will take us far beyond any of this, to a tiny camp hundreds of miles away out on the ice where the Catlin Arctic Survey explorers are nearing the end of their expedition.
WEDNESDAY 6 MAY - DAY 68 - THREE PORK SCRATCHINGS
From Ann Daniels: After 10 long days of waiting, the resupply flight finally made it to us at about 1900 on Sunday evening (that's 0345 BST, Monday 4 May).
It was a day of real expectation.
We were down to 90g-a-day of food by this time, we had our last hot meal several days before, and on Sunday we had all eaten our rations by 1600.
About halfway through our wait, Martin sent a message back to London saying that he'd only had a cup of porridge, three pork scratchings, a piece of dried coconut and a finger of shortbread. I'm afraid this prompted a worried call from his Mum!
Obviously, by this time we were all really exhausted. The lack of food had begun to affect us all - both our bodies and brains.
As we were sitting in the tent for a lot of the time, we managed to get in quite a bit of talking for a change, and we even managed to make ourselves some playing cards from Pen's notebook.
We were so glad that the flight finally came and it actually managed to land - at one point there had been some talk of them just pushing the supplies out of the aircraft door.
This would have meant none of Martin's pictures getting back, amongst other things.
Actually, after they landed, the pilots complemented us on having prepared a fantastic runway for them.
They were with us for about 45 minutes - and despite the fact that I cannot think of anybody other than Martin and Pen that I'd rather be with up here, it was great to have a chat with the pilots, Lexie (another woman!) and Kevin.
We also got messages from home, which was great.
Martin was the first to pile into the food of course - he almost made himself ill with the speed at which he ate. He also got stuck into the can of beer that the flight brought for him.
We are off again tomorrow. And I have to say I was yearning to get going again - almost a stronger yearning for me than the food.
Our spirits are restored. Now we just need our bodies to catch up.
From Pen Hadow: For the first days of waiting, Martin and I carried on drilling and taking measurements.
But we had to stop a few days before the re-supply arrived.
It simply wouldn't have been sensible, given the cold, the amount of energy that the drilling and measuring demands and the low level of calorie intake that we were down to.
I took this decision the day that Martin and I came back from drilling feeling sick and wobbly, we also took longer than usual to warm up.
The delay has been irritating for all, but up here nothing is certain and delays of this kind are always factored in.
We are now set to carry on and the drilling continues now that we have got some energising food into us.
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THURSDAY 30 APRIL - DAY 62 - FANCY AN ICY DIP?
From Ann Daniels: Well, we've been sitting waiting for the re-supply for several days now, and I've had to ration the food quite dramatically.
I'm down to about 1,000 calories a day - and I'm giving the boys a bit extra as they are still going out drilling, so they need that extra boost.
We've still got a variety of cereals and porridges for breakfast and a reasonable selection of evening meals, vitamin supplements and daytime snacks.
We just have to make sure that we use a lot less of the food than we would normally. But then, since we are not actually hauling those heavy sledges, we don't need to be taking so many calories on board anyway.
The wait here for the re-supply is a welcome break in a way.
As I'm the navigator, I am always way out front when we are trekking, which can be pretty lonely at times.
So at least at the moment we've all managed to get in some good chat.
When we were on our way to the spot where we are currently camped, we had to do our first swim of the expedition.
It's something we all dread, and it's the first time I've had to do an Arctic swim since the year 2000.
I hope we don't have too many more! It took us 20 minutes to swim across this stretch of open water.
It's nothing like getting into a swimming pool, when at least you're in control of how and when you go in.
As we see the ice around us gradually getting thinner, we assess the chances of us falling through and then we help each other into the waterproof suits.
Once you've got your suit on, you move forward step by tentative step, treading very carefully. Then suddenly, the ice breaks and you're in the water. That moment is always a shock.
We're still attached to our heavy sledges of course and although they float they're incredibly cumbersome.
Ideally, it's best to go around to the back of the sledge, climb onto it, sit astride and paddle it like a canoe - but that's exhausting and laborious, so this time I just ploughed forwards, and the sledge floated along behind me.
You feel so vulnerable. You can't use your hands, which are wrapped in plastic mitts, you can't hear or see properly because there's lots of splashing and you're so intent on keeping your chin above the water.
And you fear being trapped because the ice is always moving and can close up around you in seconds.
I never forget the power of nature. When the ice is in a benevolent state it can seem comforting - miles and miles of white all around you like a blanket. But other days, the ice makes a terrific noise when it cracks and breaks and then it seems angry, and the sheer power of it is awe-inspiring and frightening.
I've seen huge blocks of ice pushed around like sugar cubes.
I never trust it, but I feel I have a relationship with it.
From Pen Hadow: I have to say having this enforced stop is beginning to get us all down a bit.
We've been stuck here for six days now, waiting for the re-supply plane, which keeps getting delayed because of bad weather.
We've been on half rations for a while now and a combination of hunger and boredom is beginning to set in. We've been here before - but it doesn't make it any less frustrating.
The "ops" team has said that there seems to be a clear weather window coming up - so fingers crossed the flight can make it to us before the end of the week.
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THURSDAY 23 APRIL - DAY 55 - NOT ALL WHITE
From Martin Hartley: We are now into 24 hours sunshine - great for the photography. It's kind of weird there's no sunrise or sunset and we can't see Venus at night any more.
Mind you it has its good side - at least the temperature doesn't drop too much at night right now.
Most people think that it's all just white and monochrome up here. They couldn't be more wrong.
The ice can be a fantastic rainbow of colour, ranging from vivid blues and greens to yellows and even red.
The light creates odd things, too. For example, the last couple of days we have had "water skies".
That's where on an otherwise white surface you see dark water in the sky.
It's where the bottom of really low cloud reflects water on the surface in the distance - like a big stripe of metallic gun metal grey.
Pretty handy for Ann's navigation, too. It means we can avoid water "leas" way in advance.
The team members are always on the lookout for good pictures and they occasionally leave messages or arrows in the snow for me.
As time's gone on, the messages have started to get dafter; but it creates a laugh and breaks the monotony of trekking for sure.
A few days ago we had the mildest temperatures we've had so far - just minus 15C. But it came with vicious winds of around 30mph and rubbish visibility.
We decided to sit out the storm - which went on for about 24 hours - in the tent.
Even with the wild winds, we all managed to sleep for about for 17 hours solid. Just shows how tired we really were.
The next day the storm left a lot of snow over the top of breaks in the ice and unfortunately Ann fell through once up to the top of her thigh. Not much fun walking around with a cold wet leg all day.
I'm pleased say that my frostbitten toe seems to be bearing up quite well with the lovely nurse, Ann, still changing my dressing for me at the end of each day.
A couple of weeks ago it needed changing after each sledging session - so a big sigh of relief for me, and for Ann too.
I'm looking forward to getting new toe warmers on the next re-supply.
Update from Pen Hadow: Whilst we were travelling through a white-out yesterday I had an amusing thought.
The drilling has become such a part of my life now that I am indeed living out my name. My full name is in fact "Pendrill" - must be destiny!
It's worth mentioning that the four-hour drilling sessions that I am now doing with Martin's help each evening are not the only part of the whole surveying exercise.
Basically, we are undertaking a continuous surveying process from when we wake up at around 0530 in the morning until we pack up and have some food at 2000 in the evening.
In the morning after a cup of tea I defrost my outdoor clothes and go outside to start all the non-drilling measurements.
These consist of measuring snow temperature, surface snow depth, snow density and ice thickness.
Actually for the snow density, we get Ann to physically weigh specific volumes of snow. The variations can be surprising.
At around 0800, after breakfast, which Ann will have been preparing along with the rest of the day's rations, we then start off on our day's travelling.
During this travelling time, we are constantly surveying features and making observations.
On average we will note about 150 observations per day. This is where my trusty pen and clipboard have come into their own - despite all the extremes these have soldiered on perfectly.
We tend to try to set up camp again at around 1600, which gives me four hours for the drilling measurements before dinner is ready.
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THURSDAY 16 APRIL - DAY 48 - A CHANGE OF PLANS
From Pen Hadow: Well, it looks like I am going to become the drilling king of the Arctic.
After failures with our portable radar Sprite (the instrument that measures the thickness of the Arctic ice) and a fault with the SeaCat probe (a device that measures the water column beneath the floating sea ice), I'll be resorting to the old tried and tested means of manual labour to get data for the scientists.
It seems that despite all the rigorous testing, the unprecedented extremes of the Arctic have won the day.
It's a disappointment, but I'm not surprised - bits of us have frozen up too, but I'm hoping that at least a new SeaCat will come out on the next resupply.
Having said that, it's important that we keep gathering as much data as possible for analysis by the scientists, so I will be increasing my daily information-gathering activities quite dramatically.
So far, I've sent back over 1,000 separate measurements relating to snow and ice thickness, temperature and density, plus, of course, our own general observations on the landscape - rubble fields, open water and the like.
I do the drilling in the evenings before dinner and from now on I'll be doing two kinds.
The first type is on a fairly flat ice floe, from one side to the other, and the second type is an "all terrain" drilling - basically starting at the tent and heading due north, no matter what the terrain, be it thin ice, pressure ridges or rubble fields.
I measure 40m between each drilling, and I will be doing about 10 holes every evening, which takes roughly four hours (although I'll probably take a tea break after a couple of hours!).
The drill is simple and robust - so should go on for ever. It's shaped like an old fashioned car-cranking handle.
I understand the design is based on a fish drill - although at only 10cm in diameter, you wouldn't get a very big fish through this hole.
There are a series of six 80cm sections, know as "flights", which can be added the deeper you go.
Each section has a special bolt system for attaching them together, because if you had a simple screw system, like a plumber's rod, you'd never get it apart after it all froze together.
The extremely sharp drill blade section needs to be replaced after around 10 holes. The whole thing with all the bits together is 5.20m tall.
As I drill though the ice, I get what looks like an ice cornflake mound on the surface, and usually I get to about 10cm-down before going through to water.
When I'm through, I push the drill further down to remove any ice crystals, and then as it's pulled out through the hole, the sea water tends to shoot up.
I need to wait a bit for the water to settle before I can then get down to the measuring process.The first measurement is easily done with a tape measure - the water that comes up the hole naturally settles at sea level (sea level is not below the ice), so I measure the distance between the surface of the ice and the top of the water.
This usually varies between 5cm and 20cm. I then need to measure the depth of where the hole meets water. This is where I have also been driven insane by the various measuring devices we were given, which are no doubt splendid, but don't really work.
No matter - I have invented my own bomb-proof Heath-Robinson-style device that works a treat!
Essentially, I drop a metal bar vertically down the hole - when it gets to the bottom it naturally swings horizontal, at which point, I can take the measurement.
How to get it back up? Simple - there's a second piece of string attached to the end of the bar, so I have to lower it, then let the first piece of string go. Then I pull on second string and, hey presto, it's vertical and can be brought back up the hole.
After all the drilling, the kit has to be cleaned and packed up. And in order to get all of the frozen ice off the drill, I have to spend quite some time tapping and chipping away at it.
Martin and Ann say it sounds like a woodpecker - thus my new nickname in the evenings: the Arctic woodpecker.
In addition to the drilling, I also make manual notes about the thickness and type of snow around each hole.
In the mornings, before we leave, I also make observations on the ice layers, snow type, etc.
The average ice thickness seems to be between 1.5m and 2m; the fact that we are finding mainly first-year ice as opposed to multi-year ice has surprised me.
We are all OK with the amount of extra manual work that will need to be done, even though this does mean that we are slowed down from the journey point of view.
The end goal is getting the information for the scientists and that's what we are doing.
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WEDNESDAY 8 APRIL - DAY 40 - WE ARE NOT ALONE
From Pen Hadow: There's animal life everywhere in the Arctic - but we usually just can't see it.
We know that there's at least one, if not two, polar bears in the vicinity as we have seen the tracks a few times now.
We also found a fair number of Arctic fox tracks and actually saw one the other day, so there are probably one or more of them around too.
It's always mystified me what on earth a fox - albeit an Arctic one - would be doing out in this wilderness? What do they find to eat?
Well, the answer is up the food chain - they survive on scavenging the polar bear's seal kills.
Seems like a pretty tough way to exist to me, but there they are. It must be a pretty lonely existence.
We haven't seen any seals yet - but we will undoubtedly get them curiously poking their heads out through the ice as they hear our skis passing overhead - they just can't resist having a look to see what's going on.
We are of course a lot safer to investigate than the polar bears!
And of course, below the ice, there's plankton, krill, fish and a mass of other organisms that keep the food chain going.
Above the ice there is never any vegetation. But we seem to have made a breakthrough and managed to develop some sort of mould inside our sleeping bags.
Is this a first in these cold temperatures I wonder ?
We have had a relatively gentle couple of days awaiting the resupply flight.
The runway is already prepared and we spent yesterday doing general repairs to kit.
Martin spent most of the time (apart from eating and sleeping of course!) copying images to and from memory cards and repairing his ski.
The weather has closed in a bit and I hear that the resupply plane is delayed another day, so Martin will have to wait for that bacon sandwich he asked for...
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THURSDAY 2 APRIL - DAY 34 - HIGH SPIRITS
From Pen Hadow: A couple of weeks ago, we were all in pretty poor shape - suffering from truly extreme weather and terrain conditions.
The Arctic winter was truly unforgiving: temperatures of -40C and a wind chill factor making it closer to -70C, plus almost constant darkness.
You can see from Martin's frozen clothing video taken a couple of weeks ago how difficult it has been even getting dressed in the mornings!
It was hideous - but not unexpected - and we got the additional winter data that the scientists wanted, which made it all worthwhile.
But things are getting better in a lot of ways. The Arctic summer is nearly here, so we have many more light hours; the sun helps our spirits and the temperature is ranging between -34C and -38C.
One downside - our sleeping bags now get like wet sponges instead of being frozen!
Martin's desperate for a new one, so the operations team are sending one out for him on the resupply, which should turn up in a few days' time. It's the only thing he thinks about at the moment!
We covered a massive 16.7km yesterday - that's the biggest distance we've done in a day to date. So in the last 13 days we've covered 134.5km, which is amazing compared with our earlier progress.
We've noticed that the ice is older and thicker than before, but it is still very active, with ice suddenly pulling apart in front of our eyes or bashing together. The other day a lump of ice just broke off leaving Ann stranded in the middle of it - she got out pretty quickly using her skis to bridge the crack.
A while back I said we were not alone because of spotting polar bear tracks - now we've had a different kind of company.
There was a fantastic blue sky and the sun was shining when we heard this amazing roar, a bit like a tidal wave.
It got louder and louder until suddenly we realised it was a massive plane travelling super fast and very high up above us.
It flew past us twice that day, and we've seen it again three times today. Always around 2100 and 2200 UTC time. Maybe they're keeping an eye on us - who knows!
Anyway, we all look a bit tattered and torn: I've got a bad back; Ann's got a hamstring injury and Martin of course has his frostbitten toe - but we've done 14.5km today, which is great and our spirits are high.
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THURSDAY 26 MARCH - DAY 27 - THE NORTHERNMOST CAFE
From Ann Daniels: A woman's work is never done.
In the great tradition of life - alongside being the navigator, I get to do the cooking on this expedition. A pretty important job actually - it's the food that's keeping us alive and giving us the energy we need to keep going.
I guess it's not totally obvious to everybody but all the cooking absolutely must be done inside the tent, which is normally minus 30-odd. Outside would be just impossible!
The stoves have been a bit temperamental in the extreme cold recently - so to make sure I can get them to work I've been carrying bits of the pumps inside my clothes to keep them warm.
I spend a lot of time in the morning getting all the food and drinks prepared for the day - and then again cooking dinner in the evenings.
The cooking area in the tent is separated from the main sleeping area - and normally, while I'm cooking, there is a zipped up partition between me and the boys. That's because there is so much steam produced by the cooking that it would freeze and turn into snow inside the sleeping area and there's already enough snow and damp there created by condensation from our bodies.
The other thing is that the cookers make an unbelievable racket. That, combined with the howling winds outside, means that conversation during the four or more hours that I spend every day cooking is nigh on impossible.
One of the boys usually gets me a big sack of snow for melting at the beginning of each session and then I don't see them until grub's up or it's time to get going.
I remember just before we left London at the start of the expedition Martin was asked what his main fears were. He said that one of them was my cooking. Well, he doesn't seem to have any complaints now that this is the only cafe on his Earth!
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TUESDAY 17 MARCH - DAY 18 - SURVIVING ON HALF RATIONS
From Martin Hartley: It was my birthday on Tuesday.
What a way to spend it - 500 miles from the North Pole, floating on a raft of sea ice that is breaking up to the north of us, a polar bear plodding around close by and running out of food.
The resupply plane is now several days late. I know they've tried three times and the weather has stopped them, so we are now down to half rations.
So no birthday cake for me and no party.
One good thing - I did manage to record a message for my Mum that was played to her on BBC Radio Manchester on my birthday - they got her into the studio and kept my message as a surprise. I hear she was really happy, which cheered me up.
Anyway, back to our situation. When the pilot dropped us off 17 days ago he said: "Welcome to the middle of nowhere."
He was right. This is like nothing I've experienced before, but then I've never done this route before.
Because we've got to sit tight and wait for the new supplies to arrive, we are really suffering from the cold.
Because we are not on the move, and have to conserve the calories, we are fairly static and spending most of our time in the tent.
But the ambient temperature inside the tent is -40C, the inside of the tent is like an ice cavern.
I've got frostbite in my toes, my sleeping bag is full of ice and the supposedly hot food ends up like a roofing tile in seconds!
The best way to keep warm is to stay in your sleeping bag - but when that's full of camera cables as well as ice it makes for pretty uncomfortable sleeping.
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WEDNESDAY 11 MARCH - DAY 12 - FEELING THE ARCTIC CHILL
From Pen Hadow: Conditions have been hard.
We have been battered by wind, bitten by frost and bruised from falls on the ice.
Occasionally it's disheartening too when you've slogged for a day and then wake up the next morning having drifted back to where you started.
The Arctic sea ice is constantly moving, breaking open and reforming into different shapes - which means we can end up moving several kilometres in any direction while we are asleep in our tents.
The wind chill today will slice us up - it's taking the temperature down to below -50C, so we have decided to take a day's rest to recharge our batteries and soothe the aches and pains.
We are resigned to several weeks of daily discomfort and general misery, safe in the knowledge that conditions, our progress and general well-being will improve over the coming months.
This week also held another challenge - a chance to speak with some of the world's most influential climate change leaders.
What a weird feeling - here we are floating on the ice in the Arctic, and I've just had a chat with International Development Secretary Douglas Alexander and over 300 people in the audience at the Department for International Development conference on world poverty, which is being held in London.
He was asking me questions about the purpose of the Catlin Arctic Survey and why I thought it was so important.
The sat phone seemed to be pretty clear at my end and, despite the howling winds outside, I think they all heard me.
I tried to convey that climate change and the loss of the sea ice up here will affect everybody on the planet - unpredictable weather changes, rises in sea levels are all linked to food shortages and poverty.
I don't know if this is the first live link done to a conference like this, but I heard afterwards that Lord Nick Stern complained - tongue-in-cheek - that nobody had called him when he was in the Antarctic!
I'm really pleased it all worked and I hear that Gordon Brown turned up to round off just after my call.
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THURSDAY 5 MARCH - DAY 6 - A DRAMATIC NIGHT
From Pen Hadow: On Saturday we were finally dropped off at our starting point - I think we all felt a sense of wonder as the light aircraft left us alone on the ice. Excitement and anticipation for the journey ahead.
We'd been making good progress and in the first three days covered about 16.5km - taking into account the ice drifting about.
That's an average of about 5.5km a day - which might not sound like a lot, but when you are hauling 120kg of equipment I can assure you that it's good going!
Tuesday night was a bit eventful. Just after we'd eaten and were about to bed down for the night, we heard the ice breaking up around us.
It got louder at about 0300, and on checking, we saw a ridge only about 10m from the tent.
I decided that it was about time to beat a hasty retreat, which we duly did, managing to haul our gear across a narrow gap in the ice before setting up camp in a safer place.
We are now getting back on our way north, taking ice measurements with the radar along the way.
From Martin Hartley: Because of the freezing temperatures some of the equipment has been playing up - so to try to keep it functioning I'm sleeping with cables, cameras, batteries and other communications gadgets.
Sleep is difficult at the best of times - but it's even harder with this lot.
Our fast getaway from the disintegrating ice on Tuesday night has added to the sleeplessness - so we decided on a rest day.
Once we'd re-camped in a safer place, we managed to sleep through until the afternoon and when we woke up we found ourselves surrounded by open water - we expect this will freeze over during the night so that we can get on first thing in the morning.
From Ann Daniels: Martin's not the only one having problems with equipment!
I've been walking around since the first night with a fuel pump inside my clothing.
Like Martin's kit, our cooking stoves were struggling - the fuel pumps were leaking fuel - it seemed the best way to keep the pump warm!
I have to say, Pen and Martin were heroes on Tuesday night - going outside at three in the morning to check on the breaking ice - they only had their night gear on at the time so it would have been unbearably cold.
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THURSDAY 26 FEBRUARY: ONE DAY TO DEPARTURE
From Ann Daniels: I'm feeling a sense of trepidation - but at the same time quite excited. Today I am running final checks on the navigation gear, making sure things like compasses and GPS equipment are working.
As I am responsible for getting the team to the right place, I'd better get it right! Navigating up here is not like walking in a straight line North. Apart from the hazardous terrain, the ice is constantly moving - once I woke up in my tent in the morning only to find that we had drifted back to the very position we'd started that morning!
I'm also responsible for the communications from the ice, so I've been doing all the final checks on that, too. My other main task is to be expedition chef. Everything's pretty well organised on that front - in fact, all the resupply barrels are sorted and sitting in a hanger outside.
I'm looking forward to my last night for 90 days in a comfy bed. Tomorrow I'll be calling my family before I go on to the ice. That's when you know there's no turning back.
From Martin Hartley: I've not really been off duty of late - it's almost like having two jobs! In addition to sorting and helping pack group equipment and fine-tuning my personal kit, I've been on a fairly continual round of photo and video taking - trying to provide the world's media with as much material as possible before we leave.
I reckon I'll have my personal sledge all packed up by this afternoon. I'm ready to go and my mindset is now on the ice.
The only thing that still gives me shivers is the thought of falling through the ice, but then that comes with the territory. I'm looking forward to that magical world out there -with all its beauty and dangers.
From Pen Hadow: It's been a mad week - the hours we've been putting in have been daunting - prepping every item that goes out on to the ice, alongside responding to emails, taking phone calls and doing interviews.
The team has put in a superhuman effort to get to this point and it's a privilege to be a part of it. To be honest I've loved every minute of it despite feeling totally exhausted.
Actually, preparation is a key word, this project has been five years in the making and we are nearly at the culmination of five years of detailed preparation. This is an expedition like none before.
We are not in it for the adventure and glory - we are doing it to make sure that the scientists have the information they need to asses the speed that the ice cap is melting and the global implications of that.
Personally, I've been doing the last-minute checks on all the scientific boxes of tricks, and from here on in will be totally focused on the off. We have one more night in our warm safe hotel rooms and I know that we'll all make the most of that.
And a last note - it's been so mad that I'd totally forgotten it was my birthday until I got a "happy birthday" from the team today. Next week is going to be VERY different - hauling sledges for months in sub-zero temperatures for 12 hours a day. It's nearly show-time.
THURSDAY 19 FEBRUARY: WELCOME TO THE ARCTIC
From Pen Hadow: With unusually heavy snowfall in Britain just before we left for Canada, leave-taking from our families was not quite what we had planned.
My family home on Dartmoor in southwest England was left inaccessible by vehicle for four days - and this meant that I had to collect all my most personal items for the expedition as well as say goodbye to my daughter, son and wife in just 45 minutes, before setting off for London and the airport.
Our departure from Heathrow was an emotional occasion for many of us, including our families, partners and relentlessly hard-working support team.
All understand the scale of the challenge we have set ourselves and we understand the daily challenges to be faced by those we leave behind.
Four flights via Ottawa, Iqaluit and Nanisivik have got our travelling party as far as Resolute Bay in northernmost Canada.
Next week, another three flights via an abandoned weather station on an uninhabited island and a fuel stop on the Arctic Ocean's sea-ice will get us to our expedition's start point hundreds of kilometres offshore.
It is a familiar physical and psychological metamorphosis that Ann, Martin and myself have become used to over the years travelling to the High Arctic.
The landscapes from the plane windows become bereft of cities, towns and eventually even roads. Agricultural scenes give way to vast forests before the basics of rock, snow and ice take over. The planes become even smaller, sunlight is but for a handful of hours each day, and the air temperature drops towards -40C.
Welcome to the High Arctic at 75 degrees North. We love it.
After the team's frenzied work preparing more than 1.5 tonnes of equipment, clothing and food for shipment ahead of our arrival, you may imagine our horror to discover we had overtaken the entire shipment as we stepped out at Resolute.
But every cloud, however dark, has a silver lining. And for us, it was the chance for desperately needed sleep and some precious time to gather ourselves mentally for what lies ahead.
Ann has been outside for a couple of hours each day on the hills behind the village, enjoying the colour-washes of peach, blood-orange and plum cast over the snowscapes by the extended sunsets this far north.
As the team's navigator, with responsibility also for the management of the expedition's daily operations and communications, these excursions are a perfect way of gradually reconnecting with the most extreme of environments.
For Martin, too, the prospect of committing his unique photographic talents to revealing the wonders of the Arctic Ocean is apparent.
I have never seen so many camera bodies, lenses, batteries, cables, meters and cases, all spread out on his double bed.
He prefers to sleep on the floor out of respect for the tools of his trade. The agonies he will go through in deciding what items will make the cut to head north with him.
Tonight, half a tonne of our cargo was flown in, so it's been "all hands on deck" to move it all down to our base by truck and unpack it.
Tomorrow, we get to work with our final preparations for three months in sub-zero temperatures, pulling fully laden sledges weighing 100kg (200lb) more than 1,000km of floating sea-ice to the North Geographic Pole.