DOI: 10.11583/dtu.24787341.v1
title: <b>Climate Change Initiative sea ice thickness Round Robin Data Package (CCI SIT RRDP)</b>

description: All data in the CCI SIT RRDP are based on publicly available data from other sources, when using data from the CCI SIT RRDP;<b><i>Please cite this work as: </i></b><i>Olsen, Ida Lundtorp; Skourup, Henriette (2026). Climate Change Initiative sea ice thickness Round Robin Data Package (CCI SIT RRDP). Technical University of Denmark. Dataset. https://doi.org/10.11583/DTU.24787341.</i><i>This work is licensed under a CC BY 4.0 license.</i><i>Contact: Henriette Skourup, https://orcid.org/0000-0002-4468-8033, hsk@space.dtu.dk.</i><b><i>Please cite the original data source to be found in the associated paper (Olsen et al., 2024) their Table 2</i></b><br><b>Project Description:</b>The ESA Climate Change Initiative sea ice thickness Round Robin Data Package (CCI SIT RRDP) is a collection of sea ice reference observations including freeboard, thickness, draft and snow depth from sea ice-covered regions in the Northern and the Southern Hemisphere polar regions. Sea ice surface temperature and air temperature are also provided when available. The observations consist of data from airborne campaigns (laser altimetry, snow radar and EM-bird), autonomous drifting buoys, moored and submarine-mounted upward-looking sonars and visual observations from ships (ice breakers). An overview of the different data sources used in the CCI SIT RRDP and how they are acquired, by whom/when and what has been observed is presented in the Sankey diagram (<b>CCI_SIT_RRDP_Sankey, </b>credits: Renée Mie Fredensborg Hansen).The current version of CCI SIT RRDP is covering the entire polar satellite altimetry era (1993–2024). The data package has been prepared to match the spatial (25 km for the Arctic and 50 km for the Antarctic) and temporal (monthly) resolutions of satellite altimetry-derived sea ice thickness data products for a direct evaluation of these. The Equal-Area Scalable Earth Grid in version 2 (EASE2) was used to average the reference observations.The CCI SIT RRDP has been collocated to satellite-derived sea ice thickness products from CryoSat-2, Envisat and ERS-1/2 produced within the European Space Agency Climate Change Initiative (ESA CCI) and Fundamental Data Records for Altimetry (FDR4ALT). This makes it easy to use for inter-comparison with similar satellite derived products or models.The CCI SIT RRDP is organized into two zip-files, as described below, and includes data files in netCDF format.<b>CCI_SIT_RRDP</b> Include the reference observations with a file for each reference data campaign.<b>CCI_SIT_RRDPcolSatCDR</b> Include the reference observations and collocated satellite sea ice thickness observations from the CCI and FDR4ALT. There is a file for each reference data campaign and associated satellite mission (CryoSat-2, Envisat, ERS-1/2).An overview of the reference measurements included in the CCI SIT RRDP and their sources can be found in:<b>SIT_RRDP_InputData_Overview</b><b>How to Install and Run the Project: </b>Along with the final dataset is provided code to process the raw reference observations into the final RRDP file format, as well as reading and collocating the data to satellite altimetry measurements, see the associated Github repository, linked in the “Related material”.For <b>further information</b>, please, read the paper: <i>"Olsen, I. B. L., Skourup, H., Sallila, H., Hendricks, S., Hansen, R. M. F., Kern, S., Paul, S., Bocquet, M., Fleury, S., Divine, D., and Rinne, E.: Dual-hemisphere sea ice thickness reference measurements from multiple data sources for evaluation and product inter-comparison of satellite altimetry, Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2024-234, in review, 2024.</i><b>Note:</b> A revised version of this preprint has been accepted for publication in ESSD.<b>Data sources:</b><b><i>Arctic:</i></b><b>BGEP</b>: Stationary moored upward-looking sonar - Beaufort Gyre Exploration Project<b>TRANSDRIFT</b>: Stationary moored upward-looking sonar - Russian-German TRANSDRIFT project<b>NPEO</b>: Stationary moored upward-looking sonar - North Pole Environmental Observatory<b>NPI</b>: Stationary moored upward-looking sonar - from the Fram Strait Arctic Outflow Observatory by the Norwegian Polar Institute<b>Nansen Legacy</b>: Stationary moored upward-looking sonar and helicopter electromagnetic measurements - from the Nansen Legacy Project.<b>SCICEX</b>: Submarine-mounted upward-looking sonar - Submarine Arctic Science Program<b>ASSIST</b>: Visual observations from ice breakers - Arctic Shipborne Sea Ice Standardization Tool<b>OIB</b>: Airborne radar & laser altimetry & snow radar - NASA's Operation IceBridge<b>AEM-AWI</b>: Airborne (fixed-wing aircraft and helicopter) electromagnetic measurements - Alfred Wegener Institute<b>MOSAIC-HEM: </b>Helicopter-borne electromagnetic measurements - from the MOSAiC Expedition<b>N-ICE2015-HEM: </b>Helicopter-borne electromagnetic measurements - from the Norwegian Young Sea ice cruise<b>IMB-CRREL</b>: Ice mass balance buoys - Cold Regions Research and Engineering Laboratory<b>MOSAIC-SIMBA: </b>Ice mass balance buoys from the MOSAiC Expedition<b>SB-AWI</b>: Snow depth buoys - Alfred Wegener Institute<b>AEM-comb:</b> is a combination of the collocated data from AEM-AWI, MOSAiC-HEM and N-ICE2015-HEM<b><i>Antarctica:</i></b><b>AWI-ULS</b>: Stationary moored upward-looking sonar - Alfred Wegener Institute<b>OIB</b>: Airborne radar & laser altimetry - NASA's Operation Icebridge<b>SB-AWI</b>: Snow depth buoys - Alfred Wegener Institute<b>ASPeCt</b>: Visual observations from ice breakers - Antarctic Sea ice Processes and Climate