Aims and Objectives

The Arctic climate is changing fast. Near-surface warming, averaged over an area north of 60 °N is, about twice the global average. Perennial Arctic sea-ice cover is reduced at an alarming rate, glaciers in the north (including on Greenland) are retreating and permafrost (constantly frozen soil) areas are becoming smaller. This impacts the special ecology of the Arctic and local societies, but also has potential consequences for the global climate.

A view: of the Arctic Ocean Experiment 2001 ice floe, at 89 °N on 2 August 2001, before it was instrumented (Photo: Michael Tjernström)A view: of the Arctic Ocean Experiment 2001 ice floe, at 89 °N on 2 August 2001, before it was instrumented (Photo: Michael Tjernström)

Our primary tools for accessing climate change – global coupled climate models – are poorer at describing the current climate in the Arctic than anywhere else. Climate-change projections from different models differ more for the Arctic, than for any other region on Earth. The Arctic Climate Impacts Assessment (ACIA) report tells more about Arctic climate change: how it already impacts the animals, plants and people who live in the Arctic, and what the future might bring.


Arctic clouds are dominated by low-level stratocumulus and fog. Today’s climate models handle this particular type of clouds very poorly in the Arctic. We believe this is one reason for the large uncertainty in the projections of future climate.

 One reason for this poor behavior is that the sources for and lifecycle of the aerosol particles that eventually become large enough (but still very small) to become cloud condensation nuclei is different in the Arctic compared to other areas in the world. Most of the observations from which the models are built are made at the mid-latitudes and in the tropics. Aerosol particles come
from many different sources: Sea-salt particles from the ocean, sulfate particles from combustion of fossil fuels or from gases formed by biologic activity in the ocean, such as from oxidation of Dimetylsulfide (DMS ) emitted from the ocean surface during plankton blooms.

While the ice-margins in the summer Arctic are very biologically productive, and produce much DMS, the perennial ice insulates the atmosphere from the ocean. In the central Arctic, this process is only effective as long as sufficient DMS is transported in over the ice. And for each little drizzle drop that falls from the clouds down to the ice, a particle is lost forever.

Previous experiments have indicated that there are other sources of biogenic aerosol particles in the Arctic. But by and large we still have to few observations under too few different conditions to really understand how the ocean/ice/ cloud /atmosphere-system works in the central Arctic. Thus the solution to the problem is to observe this system as it evolves. Our part of the solution to the problem is thus the field experiment ASCOS, that will take place during the summer 2008. ASCOS is a multi-month Arctic field experiment based on the Swedish icebreaker Oden, plan­n­ed for the summer of 2008. The ultimate objective is to understand processes that are poorly described in
current climate models, to reduce the large uncertainty in projections of future Arctic climate.

ASCOS will improve our understanding of processes that control the evolution of clouds over the central Arctic pack ice, with an integrated study from the sea-ice interface to the cloud-topped boundary layer. The necessary interdisciplinary scientific ap­p­roach will include marine biochemistry,
aerosol and cloud chemistry/physics, and me­te­o­ro­lo­gy. ASCOS will concentrate on an ice-drift operation when Oden will be moored to an ice floe, start­ing near the North Pole and drifting passively with the ice during the biologically most active period, into autumn freeze-up, roughly July and September.

Ground-based remote sensing will provide continuous me­asurements of boundary-layer and cloud structure, while in-situ instruments and vertical pro­filing will provide detailed process-oriented data on boundary-layer dynamics, at­mos­pheric aerosol/cloud evolution and ocean/ice biochemistry. Instruments will be deployed onboard Oden and on the ice. Aerosol-cloud profiling will be conducted by helicopter from Oden. Research aircraft flying in from Svalbard will perform
complementary measurements.

The aims of ASCOS are:

· To determine the atmospheric processes that control boundary layer clouds north of 80°N.

· To determine the evolution of cloud condensation (CCN) and ice forming nuclei (IFN).

· To determine the role of boundary-layer turbulence and surface propertiesfor the exchange of heat, water, momentum and aerosols between theocean/ice/air interface and with the troposphere.

· To determine the role of marine biochemical processes for CCN and IFN formation, with emphasis on the open lead surface microlayer.

· To test and implement reliable satellite algorithms for area-covering climate monitoring.

· To provide a high-Arctic mirror-station of intense atmospheric measurements that for a limited time will sample data similar to monitoring stations around the rim of the Arctic Ocean, for example at Barrow and Alert/Eureka.

· To contribute to the data archive over the central Arctic Ocean collected during IPY.

· To provide a comprehensive data set on the high Arctic climate system, for developing and testing of integrated climate models.

The same ice floe: as on top of this page, but now from the meteorological mast during the AOE-2001 ice drift. Note the sonic anemometer in the mast to the left, the obligatory bear guard to the far left, the melt pond in front of Oden in the back, and theThe same ice floe: as on top of this page, but now from the meteorological mast during the AOE-2001 ice drift. Note the sonic anemometer in the mast to the left, the obligatory bear guard to the far left, the melt pond in front of Oden in the back, and the