Each spring since 2003, Jon Aars, senior scientist at the Norwegian Polar Institute, and his team have conducted an annual polar bear monitoring program on Svalbard - collaring, capturing and taking samples from as many bears as they can across several weeks.

By studying polar bears they get a better understanding of what is happening in this part of the Arctic environment. The bears roam over large distances and, being apex predators, provide lots of information about what is happening lower in the food chain and across different Arctic species.

The Guardian accompanied Aars on an expedition to the southern end of Spitsbergen island, the largest in the Svalbard archipelago.