**2. Sea ice thickness inversion data**

#### **2.1 Cryosat-2 altimetry satellite data**

CryoSat-2 was launched by the ESA on April 8, 2010. The Synthetic Aperture Radar Altimeter (SIRAL), carried by CryoSat-2, includes three modes of operation: Low-Resolution Measurement Mode (LRM), Synthetic Aperture Radar Mode (SAR), and Synthetic Aperture Radar Interferometry Mode (SARIn). The LRM model is primarily used to make measurements of continental ice caps and the vast majority of the Earth's ice-free ocean and land areas. The SAR model measures mainly the sea ice and some ocean basins and coastal areas. The SARIn model measures mainly the ice cap, mountain glaciers, ground-transfer currents, hydrographic basins, and the coastal zone regions. In this paper, the L1B data of the SAR model and SARIn model are used to estimate the Arctic Sea ice thickness before September 2014, and the L1B data of the SAR model is used to retrieve the whole Arctic Sea ice thickness after this time point.

#### **2.2 Sea ice density data**

The sea ice density product is used to classify the CryoSat-2 radar satellite echo signal waveforms. We use the SSM/I\_SSMIS dataset provided by the National Snow and Ice Data Center (NSIDC) to obtain sea ice density data from October 2010 to March 2012, which provides daily and monthly updates of 25 km gridded sea ice

*Spatiotemporal Variation Analysis of Arctic Sea Ice Thickness and Volume Based on CryoSat-2… DOI: http://dx.doi.org/10.5772/intechopen.112753*

density data [17, 18]. After October 2012, the MASAM2 (MASIE-AMSR2) dataset provided by NSIDC was used. Compared with the AMSR2, the MASAM2 data are less affected by the weather, have higher accuracy and resolution, and are more accurate in calculating the sea ice density during sea ice melt. The visualization of the MASAM2 data is shown in **Figure 1**.

#### **2.3 Sea ice type data**

The sea ice type data could assist in calculating the sea ice thickness. We use the Ocean and Sea Ice (OSI SAF) dataset produced by the Norwegian Meteorological Service's Ocean and Sea Ice Satellite Application Facility (OSSAF), which is a daily updated 10 km grid sea ice type product from 2005 to the present [19]. A schematic diagram of the sea ice type data visualized from the OSI SAF for March and October 2018 is shown in **Figure 2**.

#### **2.4 Sea ice snow thickness data**

As the input parameter of the sea ice static equilibrium model, the sea ice snow thickness data are directly related to the accuracy of the sea ice thickness calculation

**Figure 1.** *The MASAM2 sea ice density data.*

**Figure 2.** *Schematic diagram of the OSI SAF sea ice type products in March and October 2018*.

results. The daily updated snow thickness data from the Canada Meteorological Centre (CMC), is a dataset based on the snow depth data provided by the World Meteorological Organization Information System (WMOIS) and daily snow thickness measurements in the field [20]. A schematic of the monthly average snow thickness data for March and October 2018 for this dataset is shown in **Figure 3**.
