Baltic Sea Ice Volume from Observations Reprocessing

'''DEFINITION'''

Sea ice volume ocean monitoring indicator was introduced in Copernicus Marine Service Ocean State Report, Issue 2 (Samuelsen et al, 2018) and is derived from satellite observations product SEAICE_BAL_PHY_L4_MY_011_019. The sea ice volume is a product of sea ice concentration and sea ice thickness integrated over respective area. Sea ice concentration is the fractional coverage of an ocean area covered with sea ice. The Baltic Sea area having more than 15% of sea ice concentration is included into the sea ice volume analysis. Daily sea ice volume values are computed from the daily sea ice concentration and sea ice thickness maps. The annual course of the sea ice volume has been calculated as daily mean ice volume for each day-of-year over the period October 1992 – September 2014. Weekly smoothed time series of the sea ice volume have been calculated from daily values using a 7-day moving average filter.

CONTEXT

Sea ice coverage has a vital role in the annual course of physical and ecological conditions in the Baltic Sea. Knowledge of the sea ice volume facilitates planning of icebreaking activity and operation of the icebreakers (Valdez Banda et al., 2015; Boström and Österman, 2017). A long-term monitoring of ice parameters is required for design and installation of offshore constructions in seasonally ice covered seas (Heinonen and Rissanen, 2017). A reduction of the sea ice volume in the Baltic Sea has a critical impact on the population of ringed seals (Harkonen et al., 2008). Ringed seals need stable ice conditions for about two months for breeding and moulting (Sundqvist et al., 2012). The sea ice is a habitat for diverse biological assemblages (Enberg et al., 2018).

CMEMS KEY FINDINGS

In the Baltic Sea, the ice season typically begins in October and can last until June. The maximum sea ice volume usually occurs in March, but during the 2023/24 season, it was observed in February. That season recorded lower than average maximum ice volume of approximately 17 km³, well below the long-term climatological average. Between 1993 and 2024, the annual maximum ice volume ranged from a minimum of 3 km³ in 2020 to a peak of 51 km³ in 1996.

A statistically significant declining trend of −0.63 km³ per year (p = 0.02) is evident in the time series of maximum sea ice volume, highlighting a persistent reduction over the past three decades. Recent observations also indicate a concurrent decrease in both sea ice fraction and ice thickness, particularly in the Bothnian Bay, as reported by Singh et al. (2024), further reinforcing the regional impacts of climate change on Baltic Sea ice dynamics.

'''DOI (product):''' https://doi.org/10.48670/moi-00201