Back from hiatus
After the N-ICE2015 field campaign earlier this year, the work has continued somewhat subdued to gather and process the vast amount of data collected, and to put it into perspective. Last week 65 N-ICE researchers, representing institutes from 11 countries and many more nationalities, met in Tromsø to present and discuss the exciting data and the first findings. A big effort is made towards multidisciplinary research.
In the early phase of N-ICE2015 we were surprised by the number of severe storms that we experienced. Although the storms made our work a bit challenging, we were lucky because we now have measurements of them! We know that storms can have large effects in the Arctic — bringing lots of warm air and moisture and strong winds which affect ocean mixing and sea ice drift — and with the unique data collected during N-ICE, we have the opportunity to better understand and quantify some of these effects. But we also want to answer (or at least make some good hypotheses about) the most obvious question: Were these storms normal? For this, we step back and look at the big-picture, the large-scale circulation, over the Arctic in 2015. We have some ideas about this… so stay tuned, there’s more to come.
For the oceanography team, the impact of the ocean on the sea ice growth and melt is the main topic of investigation. A warm current from the Atlantic Ocean slowly makes its way into the Arctic and brings heat at depth below the ice. We call this the Atlantic Water inflow. Depending on oceanic circulation patterns, turbulence in the water column, and storms in the atmosphere, this heat from the Atlantic Water is sometimes brought up to the ocean surface, underneath the sea ice, where it can warm the water enough to melt the ice. By looking at currents and water characteristics below the drifting ice camps during N-ICE2015, we are able to map the location of the warm Atlantic Water. We can also estimate how much heat was transferred to the sea ice. When and why did this warm water rise up to the ice is what we will be working on in the foreseeable future!
The change in redistribution of sea ice and snow mass due to sea ice thinning is one of the crucial consequences of the shift from the multiyear sea ice towards a thinner first year ice regime. The data gathered by precise GPS stations, autonomous drifter buoys, ship radar and satellite images on sea ice drift and deformation on spatial scales of centimeters to hundreds of kilometers and temporal scales of seconds to weeks will allow us to improve the representation of sea ice dynamics in climate models.
The sea ice during the N-ICE2015 campaign was covered with thick snow. Already in January around 50 cm had accumulated on the ice. Snow isolates the sea ice from the cold atmosphere and reduces sea ice growth and light transmission through the ice, the latter is important for biology. Further, the heavy snow load may also increase the occurrence of snow-ice and superimposed ice. Snow-ice formation was observed already in winter and spring, when the heavy snow load caused the ice surface to sink below sea surface level causing flooding of the ice surface. Cold air temperatures lead to a freezing of the slushy snow. Superimposed ice forms from refreezing of snow melt at the top of the ice surface. This phenomenon is mainly observed during summer when heating causes snow melt and this water drains to the colder ice below. Both processes have a positive impact to the sea ice mass balance and will perhaps play a bigger role in seasonally ice covered Arctic than previously assumed.
During the campaign, the marine ecosystem was also studied. Primary producers in particular were in focus, looking at how they respond to changes in the ice cover. Hot spots of algal activity were found in unexpected places such as the first year ice ridges, and below the thick snow cover. Interestingly, the algal bloom that developed in the water column was formed by a different algal species than usual. We are currently linking these observations with the amount of light and nutrients available for algal growth below the pack ice, to determine the implications that these shifts in algal communities composition and primary production might have for the Arctic marine ecosystem.
Over the next months we hope to report more in detail on these early findings, so stay tuned.