Arctic Sea and Sea Ice Surface Temperature 2D trend from climatology based on reprocessed observations

'''DEFINITION'''The OMI_CLIMATE_sst_ist_ARCTIC_sst_ist_trend product includes the cumulative/net trend in combined sea and ice surface temperature anomalies for the Arctic Ocean from 1993-2022. The cumulative trend is the rate of change (°C/year) scaled by the number of years (30 years). The SST/IST Level 4 analysis that provides the input to the trend calculations are taken from the reprocessed product SEAICE_ARC_PHY_CLIMATE_L4_MY_011_016 with a recent update to include 2022. The product has a spatial resolution of 0.05 degrees in latitude and longitude.Since the SEAICE_ARC_PHY_CLIMATE_L4_MY_011_016 is currently only available until the 30th June 2022, an adjusted version of the SEAICE_ARC_SEAICE_L4_NRT_OBSERVATIONS_011_008 product has been used for the rest of 2022. The adjustment is based on the biases between the NRT and reprocessed product during the second half of 2021 and was made to ensure consistency in the OMIs. The OMI time series runs from Jan 1, 1993 to December 31, 2022 and is constructed by calculating monthly averages from the daily level 4 SST/IST analysis fields of the SEAICE_ARC_PHY_CLIMATE_L4_MY_011_016 product from 1993 to 2022. See the Copernicus Marine Service Ocean State Reports (section 1.1 in Von Schuckmann et al., 2016; section 3 in Von Schuckmann et al., 2018) for more information on the temperature OMI product. The times series of monthly anomalies have been used to calculate the trend in surface temperature (combined SST and IST) using Sen’s method with confidence intervals from the Mann-Kendall test (section 3 in Von Schuckmann et al., 2018).'''CONTEXT'''SST and IST are essential climate variables that act as important input for initializing numerical weather prediction models and fundamental for understanding air-sea interactions and monitoring climate change. Especially in the Arctic, SST/IST feedbacks amplify climate change (AMAP, 2021). In the Arctic Ocean, the surface temperatures play a crucial role for the heat exchange between the ocean and atmosphere, sea ice growth and melt processes (Key et al., 1997) in addition to weather and sea ice forecasts through assimilation into ocean and atmospheric models (Rasmussen et al., 2018). The Arctic Ocean is a region that requires special attention regarding the use of satellite SST and IST records and the assessment of climatic variability due to the presence of both seawater and ice, and the large seasonal and inter-annual fluctuations in the sea ice cover which lead to increased complexity in the SST mapping of the Arctic region. Combining SST and ice surface temperature (IST) is identified as the most appropriate method for determining the surface temperature of the Arctic (Minnett et al., 2020). Previously, climate trends have been estimated individually for SST and IST records (Bulgin et al., 2020; Comiso and Hall, 2014). However, this is problematic in the Arctic region due to the large temporal variability in the sea ice cover including the overlying northward migration of the ice edge on decadal timescales, and thus, the resulting climate trends are not easy to interpret (Comiso, 2003). A combined surface temperature dataset of the ocean, sea ice and the marginal ice zone (MIZ) provides a consistent climate indicator, which is important for studying climate trends in the Arctic region.'''CMEMS KEY FINDINGS'''SST/IST trends were calculated for the Arctic Ocean over the period January 1993 to December 2022. The cumulative trends are upwards of 2°C for the greatest part of the Arctic Ocean, with the largest trends occur in the north Barents Sea, Kara Sea and the Eurasian part of the Arctic Ocean. Zero to slightly negative trends are found at the North Atlantic part of the Arctic Ocean. The combined sea and sea ice surface temperature trend is 0.122+/-0.008°C/yr, i.e. an increase by around 3.66°C between 1982 and 2022. The 2d map of Arctic anomalies reveals regional peak warmings exceeding 10°C. '''Figure caption'''Cumulative trends in combined sea and sea-ice surface temperature anomalies calculated from 1993 to 2022 for the Arctic Ocean (OMI_CLIMATE_sst_ist_ARCTIC_sst_ist_trend). Trend calculations are based on the multi-year Arctic Ocean L4 SST/IST satellite product SEAICE_ARC_PHY_CLIMATE_L4_MY_011_016.'''DOI (product):''' https://doi.org/10.48670/mds-00324