Catlin Arctic Survey: Images from the ice

The expedition members: Ann Daniels, Martin Hartley and Pen Hadow Photograph: Martin Hartley/CAS

Pen Hadow, kit and tent Photograph: Martin Hartley/CAS

Ann Daniels in the tent sorting out equipment Photograph: Martin Hartley/CAS

Ann Daniels and Pen Hadow in tent getting on with daily life Photograph: Martin Hartley/CAS

Pulling kit on skis Photograph: Martin Hartley/CAS

Defrosted lead on ice sheet Photograph: Martin Hartley/CAS

Testing ice sheet before crossing Photograph: Martin Hartley/CAS

Getting ready to cross defrosted lead Photograph: Martin Hartley/CAS

Crossing defrosted lead Photograph: Martin Hartley/CAS

Ice sheet Photograph: Martin Hartley/CAS

Struggling with kit Photograph: Martin Hartley/CAS

Taking sample of ice sheet Photograph: Martin Hartley/CAS

Pen Hadow carries Mora ice drill Photograph: Martin Hartley/CAS

On the ice sheet Photograph: Martin Hartley/CAS

The Catlin Arctic Survey, led by explorer Pen Hadow, is trekking on foot to the North Pole. The team were dropped on the ice on 2 March and are collecting data about the sea ice en route Photograph: Martin Hartley/CAS

Pen Hadow: the leader of the Catlin Arctic Survey expedition Photograph: Martin Hartley/CAS

Team-member Ann Daniels struggles with sledge Photograph: Martin Hartley/CAS

The team must drag their sledge carrying tents, supplies and scientific equipment over ice boulders. Each sledge weighs up to 120kg Photograph: Martin Hartley/CAS

Pen Hadow and Ann Daniels taking a well-earned rest Photograph: Martin Hartley/CAS

Pen Hadow and Ann Daniels crossing a refrozen lead. The floating ice is constantly moving, so forward progress can be lost by drifting ice taking the team southwards Photograph: Martin Hartley/CAS

Pen Hadow (in blue) and Ann Daniels (red) navigating their path through an ice ridge in the Arctic Ocean. Cracks can open up in the pans of ice and pressure at the edges can create ridges up to 5m high Photograph: Martin Hartley/CAS

After initially struggling against high winds and temperatures, which dropped to -40C (up to -70C with wind chill) the team is now making quicker headway on their northwards journey Photograph: Martin Hartley/CAS

Ann Daniels described a terrifying night during which the ice around the team's tent began to crack up Photograph: Martin Hartley/CAS

Pen Hadow drilling into the sea ice to collect data Photograph: Martin Hartley/CAS

The Catlin Arctic Suvey is collecting data about the Arctic sea ice to provide a benchmark against which future changes due to climate change can be measured Photograph: Martin Hartley/CAS

The mission control room in London can monitor the explorers' health in real time Photograph: CAS

Martin Hartley is the expedition photographer Photograph: Martin Hartley/CAS