• Canada
• OA Publications Mandate: No close

Following the polar amplification of global warming in recent decades, we have witnessed unprecedented changes in the coverage and seasonality of Arctic sea ice, enhanced freshwater storage within the Arctic seas, and greater nutrient demand from pelagic primary producers as the annual duration of open-ocean increases. These processes have the potential to change the phenology, species composition, productivity, and nutritional value of Arctic sea ice algal blooms, with far-reaching implications for trophic functioning and carbon cycling in the marine system. As the environmental conditions of the Arctic continue to change, the habitat for ice algae will become increasingly disrupted. Ice algal blooms, which are predominantly species of diatom, provide a concentrated food source for aquatic grazers while phytoplankton growth in the water column is limited, and can contribute up to half of annual Arctic marine primary production. Conventionally ice algae have been studied as a single community, without discriminating between individual species. However, the composition of species can vary widely between regions, and over the course of the spring, as a function of local environmental forcing. Consequently, current approaches for estimating Arctic-wide marine productivity and predicting the impact of climate warming on ice algal communities are likely inaccurate because they overlook the autecological (species-specific) responses of sea ice algae to changing ice habitat conditions. Diatom-ARCTIC will mark a new chapter in the study of sea ice algae and their production in the Arctic. Our project goes beyond others by integrating the results derived from field observations of community composition, and innovative laboratory experiments targeted at single-species of ice algae, directly into a predictive biogeochemical model. The use of a Remotely-Operated Vehicle during in situ field sampling gives us a unique opportunity to examine the spatio-temporal environmental controls on algal speciation in natural sea ice. Diatom-ARCTIC field observations will steer laboratory experiments to identify photophysiological responses of individual diatom species over a range of key growth conditions: light, salinity and nutrient availability. Additional experiments will characterise algal lipid composition as a function of growth conditions - quantifying food resource quality as a function of species composition. Furthermore, novel analytical tools, such as gas chromatography mass spectrometry and compound specific isotope analysis will be combined to better catalogue the types of lipid present in ice algae. Field and laboratory results will then be incorporated into the state-of-the-art BFM-SI biogeochemical model for ice algae, to enable accurate simulations of gross and net production in sea ice based on directly observed autecological responses. The model will be used to characterise algal productivity in different sea ice growth habitats present in the contemporary Arctic. By applying future climate scenarios to the model, we will also forecast ice algal productivity over the coming decades as sea ice habitats transform in an evolving Arctic. Our project targets a major research gap in Phase I of the CAO programme: the specific contribution of sea ice habitats to ecosystem structure and biogeochemical functioning within the Arctic Ocean. In doing so, Diatom-ARCTIC brings together and links the activities of ARCTIC-Prize and DIAPOD, while further building new collaborations between UK and German partners leading up to the 2019/20 MOSAiC campaign.

Efficient air traffic management depends on reliable communications between aircraft and the air traffic control centres. However there is a lack of ground infrastructure in the Arctic to support communications via the standard VHF links (and over the Arctic Ocean such links are impossible) and communication via geostationary satellites is not possible above about 82 degrees latitude because of the curvature of the Earth. Thus for the high latitude flights it is necessary to use high frequency (HF) radio for communication. HF radio relies on reflections from the ionosphere to achieve long distance communication round the curve of the Earth. Unfortunately the high latitude ionosphere is affected by space weather disturbances that can disrupt communications. These disturbances originate with events on the Sun such as solar flares and coronal mass ejections that send out particles that are guided by the Earth's magnetic field into the regions around the poles. During such events HF radio communication can be severely disrupted and aircraft are forced to use longer low latitude routes with consequent increased flight time, fuel consumption and cost. Often, the necessity to land and refuel for these longer routes further increases the fuel consumption. The work described in this proposal cannot prevent the space weather disturbances and their effects on radio communication, but by developing a detailed understanding of the phenomena and using this to provide space weather information services the disruption to flight operations can be minimised. The occurrence of ionospheric disturbances and disruption of radio communication follows the 11-year cycle in solar activity. During the last peak in solar activity a number of events caused disruption of trans-Atlantic air routes. Disruptions to radio communications in recent years have been less frequent as we were at the low phase of the solar cycle. However, in the next few years there will be an upswing in solar activity that will produce a consequent increase in radio communications problems. The increased use of trans-polar routes and the requirement to handle greater traffic density on trans-Atlantic routes both mean that maintaining reliable high latitude communications will be even more important in the future.