Sea ice plays a crucial role on the ocean and is one of the most sensible indicators of climate change (IPCC 2013). The changing sea ice can be characterized by 4 Essential Climate Variables (ECVs) identified by the World Meteorological Global Organization Climate Observing System implementation plan (WMO Pub No.GCOS-200) : 1) sea ice extent, 2) sea ice concentration, 3) sea ice drift and 4) sea ice thickness. Since the 70ies, these 3 first variables are fairly well observed from space. However, before 2010 and the launch of CryoSat-2, sea ice thickness observations remain sparse and un- homogeneously distributed over time and space. In the Arctic ocean, we will show in this presentation that sea ice thickness time series can be extended to at least 16 years (2002-2017) using Envisat, CryoSat-2 and Sentinel-3 satellites with inter-missions biases calibrated and corrected. Among all potential inter-mission biases, the most impacting is certainly the transition from Low Resolution Mode (LRM) to Synthetic Aperture Radar (SAR) altimetry. This transition is particularly important over sea ice considering that the strong roughness heterogeneity, at basin scale and within the radar footprint, has different signatures in LRM and SAR modes. Here, we will focus on the transition between Envisat and CryoSat-2 common flight period (20010-2012). Results are validated against in situ observations (mooring, airborne, buoys and laser altimetry). This same methodology is applied to produce equivalent long term time series over Antarctica (2002-2017). In the southern ocean, the main difficulties rely on the severe lack of in-situ observations and on the ability to retrieve the snow depth. First results based on the Saral and Cryosat Ka-Ku frequency radar differences will be shown. Finally, we explain how this new global sea ice volume changes will provide new insights on the response to climate change. In particular, the final objective is to revisit the ocean freshwater budget and to provide a new constraint on the land ice melt contribution to sea level rise that is independent from the NASA Gravity Recovery and Climate Experiment measurements.