Ecosystem functions controlled by sea ice and light in a changing Arctic
Eco-Light is a collaborative project of the British Antarctic Service (BAS), the sections Sea Ice Physics and Polar Biological Oceanography at the Alfred Wegener Institute (AWI), the University College London (UCL) and Ocean Atmosphere Systems GmbH (OASys).
The Arctic is warming more than twice as fast as any other region of our planet. This warming has led to quantifiable changes right across the Arctic on land, in the ocean and the atmosphere. The most dramatic changes are those associated with Arctic sea ice whose extent has decreased by around 50% in the last three decades. The Arctic is no longer a region dominated by a thick multi-year ice (MYI); it is now a regime controlled by thinner, more dynamic, first year ice (FYI). The Arctic is experiencing a shift from a year-round sea-ice cover to a seasonal regime. In fact, complex computer models predict that the Arctic Ocean is on track to become mostly ice free in summer within a few decades, if not earlier.
These changes have important implications for the Arctic marine ecosystem since its functioning is mainly driven by the seasonality and the physical properties of the sea ice. Our understanding of the functioning of the Arctic marine ecosystem has been overwhelmingly derived from a MYI setting, rather than the FYI dominated Arctic of recent years. Thus, our current state of knowledge of these processes and the validity of many of the parameterisations presently embedded in computer models become more questionable.
Light is one of the critical drivers of primary production in and under sea ice by acting as a trigger for sea-ice algae and phytoplankton blooms. Recent studies revealed that that the transition from MYI to FYI ice cover corresponds to an increase of 200% in light transmittance into the upper ocean. Therefore, if we are to understand and predict ecosystem function in this ‘new Arctic’, we must understand and correctly parameterise the light climate under this new FYI environment we find ourselves in today, and for the foreseeable future. To do this correctly we need a holistic approach that seamlessly brings biology, optics, sea ice and ocean physics, together with satellite remote sensing and cutting-edge modelling. Eco-Light embodies this approach.
Eco-Light will provide fundamental data to improve parameterisations of physical processes, as well as biogeochemical and ecosystem processes in the snow, sea ice and upper ocean. Questions like the following drive this research:
- How does this new Arctic influence light penetration through ice and snow?
- How will the ecosystem respond to changes in light conditions and food availability?
To tackle those science questions, we collaborate also with the Korean Polar Research Institute. In August 2019 we participated in an expedition to the Chukchi Sea in the Pacific region of the Arctic Ocean with the research vessel ‘ARAON’. Here, in-situ measurements of light transmission through sea ice and snow were taken, in conjunction with primary production data. In addition, a set of buoys were deployed, which were intended to measure light transmission and biological data over the course of a seasonal cycle (Fig. 1)