Isotopes of nitrogen

• These are objectively true statements that most people have come to accept.
• But it is also true that Earth’s climate has never been stagnant and climate anomalies have been frequent throughout the past.
• Are the impacts of modern climate change comparable to those of the medieval warm period (MWP) or the little ice age (LIA)?

Ecosystem background

• Predators at the top of the food chain, like polar bears, reflect changes across the entire ecosystem, all the way down to microscopic algae.
• In the Arctic, the base of the food web is sourced from two categories: sea ice-associated algae and open-water phytoplankton, which are distinguishable through their carbon isotopes.

Results from our study

• In our study we examined stable carbon and nitrogen isotopes in polar bear bone collagen.
• The polar bears were all from the Lancaster Sound sub-population and spanned the last 4,000 years.

What it all means

• The results of the nitrogen isotopes showed that throughout time, 4,000 years BP to the present, the structure of the Lancaster Sound food web was relatively unchanged.
• Polar bears eat seals, seals eat cod, cod eat zooplankton, et cetera.
• There were no surprising shifts in the diets of polar bears despite past and present climate change.

Evidence of a warming climate

• For ringed seals, the primary prey of polar bears, it is a platform for denning and raising young.
• In this case, we have illustrated the magnitude of difference occurring in the modern Arctic, relative to past climate anomalies.
• We can, therefore, not dismiss calls to action on climate change on the basis that the climate has always fluctuated.