The University of Colorado Polar and Paleoclimate Modelling Group studies Arctic sea ice and ocean variability, future projected changes in the Arctic Ocean, and Earth’s past polar climate.
The main tool we use is global climate models in combination with available observations. The Polar and Paleoclimate Modelling Group was established in 2015 when Alexandra Jahn joined CU as an Assistant Professor.
In addition to Professor Jahn, the research group includes undergraduate students, graduate students, and postdoctoral researchers who spend between a few months and several years in the group.
What are climate models and how are they used?
Climate models represent our understanding of the climate system in terms of mathematical equations, which are solved numerically on large supercomputers.
The climate models we use are primarily coupled climate models that participate in the Climate Model Intercomparison Project (CMIP). Coupled climate models include, at a minimum, representations of atmospheric processes and oceanic processes, but these days usually also include representations of sea ice, land surface properties, river runoff, and often even of the carbon cycle.
To produce future projections, these climate models are driven by different possible future emission scenarios to assess the range of possible future climate states. For CMIP, the forcing scenarios are the same for all models, so model projections differ due to differences in the representations of different parts of the climate system as well as due to natural variability.
The model projections obtained from the climate models participating in CMIP inform the Intergovernmental Panel on Climate Change (IPCC) reports and represent the best projections of future climate change. Knowing how the climate system may change in the future is important for mitigation and adaptation planning.
What can we learn about Arctic climate change using climate models?
Climate model projections show that Arctic sea ice loss will continue in the next decades under all physically possible emission scenarios.
In fact, they show that we may reach a practically ice-free Arctic Ocean at the end of summer for the first time by 2050 under all emission scenarios.
A practically ice-free Arctic Ocean is defined as the Arctic Ocean where over 93% of the ocean is open water without sea ice, with just 1 million km2 of sea ice remaining north of Greenland and the Canadian Arctic.
However, if global warming remains under 1.5°C globally, ice-free conditions will remain the exception. In comparison, for warming above 2.5°C, an ice-free Arctic will be a frequent occurrence and could last several months by the end of the 21st century.
Research interests
- Projections of future Arctic sea ice loss
- Understanding the variability of Arctic sea ice
- Modelling microplastics in Arctic sea ice
- Assessing oceanic and sea ice fluxes from the Arctic to the North Atlantic
- Past changes in the earth’s polar climate, ranging from the recent past to millions of years ago
