Introduction: our plan

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Our deployment strategy is predicated on two principles: key location and collocation. The limited numbers of IMBs are deployed strategically to optimize the observation of changes and trends in sea ice throughout the Arctic Basin. The locations are influenced by model results and previous observations. The IMBs have routinely been collocated with other sensor packages. The value of any of these individual measurement systems, including the IMB, is greatly enhanced when they are operated in a coordinated fashion. This integration is critical to developing a Sustainable Arctic Observing Network. For example, collocating IMBs with oceanic and atmospheric measurement systems provides a complete profile of atmosphere, ice and upper ocean properties. Such an integrated set of observations is needed to be able to understand the environmental changes that are occurring. Data from these instruments can be used to validate and calibrate remote sensing tools, including satellite-based observations of ice thickness, snow depth measurements,  and onset dates of melt and freezeup. They can also be assimilated into numerical models to provide a context for the data and a predictive capability.

Functioning Ice Mass Balance buoys as of 1 September 2008. The buoys were deployed in conjunction with the NPEO, the BGEO, and DAMOCLES. The magenta circles denote possible locations for new buoy deployments.
 

One key element of our deployment plan is to continue our long-term partnerships with the North Pole Environmental Observatory (NPEO) [Morison et al., 2002] and the Beaufort Gyre Environmental Observatory (BGEO). The NPEO has been operating since 2000 and has a team of several different investigators regularly deploying instruments including an IMB, an ice-tethered ocean profiler, an ocean flux sensor, a meteorological station, and a sea floor mooring. The Beaufort Gyre is hypothesized to be a flywheel of the Arctic Ocean circulation [Proshutinsky et al., 2002] i) regulating variability of sea ice drift, thickness and concentration; ii) accumulating and releasing freshwater and heat; and iii) interacting with the Greenland Sea Gyre to promote decadal variability of the Arctic climate.  Beginning in 2003 the IMBs have been deployed at the BGEO with an ice-tethered ocean profiler and an ocean flux sensor,.

We recognize the importance of international collaborations in building a Sustainable Arctic Observing Network.  Towards this end, we will also continue our established collaboration with the European Union scientists involved with Developing Arctic Modelling and Observing Capabilities for Long-term Environmental Studies (DAMOCLES) project. Our ongoing AON-IPY project has been fully integrated with DAMOCLES, with 10 IMBs having been deployed as an element of the extensive DAMOCLES atmosphere-ice-ocean observing array.

Specific site locations for the moorings are determined using ice thickness distributions generated by sea ice dynamics models. New sites are located to take advantage of existing measurement sites and activities and historical data records, including the North Pole Environmental Observatory, the International Arctic Buoy Program, and the SCICEX cruises. The eventual goal is a  comprehensive, sustainable Arctic-wide  network of autonmous sensor systems.
 

The ice thickness is monitored with a combination of moored ice-profiling sonars (IPS) and drifting ice mass balance buoys (IMB). Model estimates of the basin-wide mean annual ice thickness are used to guide deployment of the moored ice-profiling sonars (IPS). Currently we are using the Polar Science Center Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS) model, operated by Jinlun Zhang. PIOMAS is a coupled ice/ocean model with a spatial resolution of 40 km, driven by NCEP/NCAR reanalysis surface air pressure and air temperature field.

Early results from the model (see plot on right) suggest that data from an IPS site in the Chukchi Sea, north of Barrow, Alaska, coupled with results from an existing IPS site at the North Pole could explain 90% of the variance of the basin-wide, annual mean thickness. This compares to a maximum total variance of 72% at a single point not far removed from the North Pole.