Laurynas Klimavičius, Egidijus Rimkus

Future projections of false spring events in the eastern part of the Baltic Sea region

Santrauka In recent decades, rising winter and spring temperatures have led to an earlier onset of the growing season. However, this shift is often accompanied by false spring (FS) events – situations when the last spring frost (LSF) occurs after the start of the growing season (SGS). This study evaluates future changes in the recurrence and intensity of FS events in the eastern part of the Baltic Sea region. The SGS and LSF dates for each grid cell within the study area for each year were determined to identify FS events. An FS event was recorded when LSF occurred later than the SGS date. The intensity of FS events was assessed using growing degree days (GDD) accumulated until the event. Future projections were generated using five CMIP6 models (CanESM5, ACCESS-CM2, GFDL-CM4, MPI-ESM1-2-LR, and NorESM2-MM), two SSP scenarios (SSP2-4.5 and SSP5-8.5), and data obtained from the NASA NEX-GDDP-CMIP6 dataset. The period from 1995 to 2014 was used as the baseline, and projections were made for the years 2041–2060 and 2081–2100. Analysis showed that SGS and LSF dates are projected to shift significantly earlier under all models and scenarios. However, FS recurrence projections are less consistent. Most models indicate a decline in FS events by mid-century, while forecasts for 2081–2100 are mixed – two models suggest an increase, while the other three suggest a decrease. The mean GDD sum accumulated until the FS event increases only when the frequency of FS events is projected to rise, suggesting that future FS events may be more intense

Doi https://doi.org/10.5200/baltica.2025.2.4

Raktažodžiai spring frost; growing season; compound climate events; Baltic States

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