The Roadmap document (D5) has identified observational gaps and additional work required to achieve better sea ice mass estimates. The following points were discussed:
- For the product generation and validation there should be a common validation procedure and data set .
- Future validation campaigns should include dedicated data acquisitions both over first and multiyear ice.
- Using a synergy of data from the radar altimeters and different sensors (SMOS, AVHRR,APPP-x,ICESAT-2) is recommended.
- It is recommended that the next generation polar altimeter is launched with sufficient overlap to previous altimeter platforms to allow the estimation of inter-mission biases.
- For the future Impact Assessment it is recommended to compile a SIMRE product for the whole Arctic on regional scales and with spatial resolutions comparable to the model. An appropriate interpolation method of the pole hole, where no CryoSat data are available, needs to be designed.
- For the future Impact Assessment more advanced assimilation of data into the model is required. In addition, assimilation should not only be carried out once per year like in our study (Nov/Dec), but on a continuous basis to avoid that the model slowly drifts back into its mean state as observed here.
- For the future modelling and forecasting it is recommended to retrieve also thickness distributions from CryoSat data.
- Efforts to produce sea ice thickness over the summer season are ongoing but were beyond the reach of this project, however the initialization of the model with the April ice thickness can help predict the summer conditions of sea ice in the Arctic.
The D5 Scientific Roadmap discussed the potential for integrating the data into current observational and modelling initiatives. The SIMRE ensemble data integrates number of different individual products and provides bounds of uncertainty.However, SIMRE needs to be compiled over the whole Arctic for the whole CryoSat life span. The project provides the following recommendations:
- Compilation of SIMRE with other earlier prior to CryoSat-2 will allow for the assessment of the long-term changes therefore would be useful for the climate change assessments (i.e. IPCC).
- SIMRE product can be used to improve the short-term model forecasts of sea ice.
- SIMRE provides a first estimate of uncertainties in the sea ice thickness products, however a proper error estimate analysis is required in the future for the individual products.
- For both better observational use and better short-term forecast modelling the SIMRE data also need to be provided in more real-time. This is absolutely necessary for operational forecast systems. , Alternatively, the global SIMRE product could be regularly updated and serve as a reference dataset for evaluations and sensitivity studies.
The Scientific agenda for the next 5 years and key partners:
From the achievements and knowledge gaps discussed above a clear scientific agenda for the next 5 years can be proposed. It consists of the components listed below. It is clear that thorough progress depends on the involvement of a number of key partners related to these components. Without mentioning specific groups or names, these are:
- Satellite retrieval algorithm experts
- Validation data and implementation experts
- Data assimilation and model inversion experts
- Model developers and end users
- Sea ice, ocean, and atmosphere experts
- Closer coordination with operational end users
- Closer coordination with space program and future mission managers
The points discussed in the Roadmap were:
- Compile consistent and Arctic wide reconciled ensemble data set of satellite derived ice thickness including information about its uncertainty.
- Improve product validation
- Improve merging of observational and model data.
- Assess consequences of Arctic sea ice change
- Improve use of ice thickness products for operational applications.
- Assure mission continuity
The transition between scientific and operational activities was discussed in D5. The operational use of altimeter based sea ice thickness estimates is increasing, exercises like SIMRE are crucial in guiding the users in choosing the right product for their need. Thus, operational needs like seasonal forecasting and NRT high resolution estimates should be directly assessed in the future SIMRE. There are research questions that need more investigations and answering them would build confidence in sea ice thickness products:
- Does the forecast skill of a seasonal ice forecast model depend on the SIT product used for initialization or assimilation.
- What is the impact of different product on tactical decisions to be made in ice navigation
A main requirement of operational data is the real-time availability of data. While it has been demonstrated that CryoSat data products can be provided in near real time in general, it is a matter of financial and personnel resources to be able to provide services 24/7 and to assure smooth processing and dissemination of data products. On the one hand, this could be achieved by transferring processing algorithms and systems directly to the operational centers and relieving scientific research groups from the burden of operational activities. On the other hand, this also requires additional resources at the operational centers. In the case of a SIMRE product the process is complicated by the fact that different data centers have to provide their products in near real time first before they can be merged to form an ensemble and then used in an operational context. Again, if operational centers would process the data with all different algorithms it would add to their effort and cost.