The Water Cycle of the Baltic Sea Region From GRACE/GRACE-FO Missions and ERA5 Data

Boulahia, Ahmed Kamel; García-García, David; Vigo, M. Isabel; Trottini, Mario; Sayol, Juan Manuel

doi:10.3389/feart.2022.879148

“…( 1 ), the total volume change in the entire Baltic Sea was estimated to amount about 198 . For comparison, the mean climatological annual freshwater surplus (sum of river run-off, precipitation, and evaporation) in the Baltic Sea is about 480 28 , 29 . The total volume change can be separated between the Belt Sea and the Sound Sea (see Methods) and then amounts to 169 and 29 , respectively, giving a ratio of 8:1.4, which is close to the previously estimated ratio of 8:2 30 .…”

Section: Resultsmentioning

confidence: 99%

Observation of a moderate major Baltic Sea inflow in December 2023

Purkiani,

Jochumsen,

Fischer

2024

Sci Rep

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Just before Christmas 2023, the low-pressure system storm “Zoltan” struck Germany, resulting in widespread damage and two consecutive large storm surges on the North Sea coast in the night from Thursday 21 December 2023 to Friday 22 December 2023. Storm Zoltan brought heavy rainfall, accompanied by thunderstorms and winds ranging between 90 and 115 $$\mathrm {km\,h^{-1}}$$ km h - 1 , with gusts reaching up to 140 $$\mathrm {km\,h^{-1}}$$ km h - 1 along the coast which caused severe damage, particularly in northern Germany. Characteristics of the inflowing water at the Fehmarn Belt buoy (FEB), Darss Sill station (DAR) and the Arkona Basin buoy (ARK), including salinity, temperature, dissolved oxygen and ocean currents properties, were analysed to understand the impact of storm Zoltan in the western Baltic Sea. In addition to the damage along its path, following the onset of strong westerly winds associated with storm Zoltan, a large volume of water, containing saline (17–22 psu), cold (5–6 °C), and oxygen-rich 7–8 ($$\,\mathrm { ml\,l^{-1}}$$ ml l - 1 ) water from the Kattegat and the North Sea reached into the western Baltic Sea. The sea level at Landsort Norra increased by +57 cm over a period of 14 days, from 15 December to 29 December 2023. This resulted in a total volume change of 198 $$\mathrm {km^3}$$ km 3 in the entire Baltic Sea, with 169 $$\mathrm {km^3}$$ km 3 and 29 $$\mathrm {km^3}$$ km 3 provided via the Belt Sea and the Sound Sea, respectively. Observations at the DAR indicated a significant inflow between 19 December 2023 and 1 January 2024 with salinity above 13 psu, temperature below 5.5 °C and dissolved oxygen of about 7.5–8 $$\mathrm { ml\,l^{-1}}$$ ml l - 1 . While the maximum salinity of the bottom layer at the DAR was about 17 psu, the ARK exhibited significantly higher salinities, reaching up to 22 psu at the bottom layer. During the main inflow period, 75 $$\mathrm {km^3}$$ km 3 of highly saline water entered the western Baltic Sea. This corresponds to an average salt transport of 1.75 Gt into the western Baltic Sea (1.39 Gt from the Belt Sea and 0.36 Gt from the Sound Sea), representing more than 20% of the total annual salt import into the Baltic Sea), which places the event in the moderate range of major Baltic inflows. This event brought an amount of about 0.8 $$\mathrm {10^6}$$ 10 6 t oxygen into the Baltic Sea. This was the strongest inflow into the Baltic Sea since 2016.

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Increase in marginal sea alkalinity may impact air–sea carbon dioxide exchange and buffer acidification

Cotovicz,

Cahill,

Sabbaghzadeh

et al. 2024

Limnology & Oceanography

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Total alkalinity (TA) has increased in the Baltic Sea, with implications for atmospheric CO2‐induced acidification and CO2 uptake. We compiled extensive data of TA in surface waters of the Baltic Sea, aiming to (i) identify new tendencies in the relationship between TA and salinity (TA–S relationship), (ii) update the TA trend analysis, (iii) investigate spatial–temporal patterns, and (iv) discuss potential drivers and implications. We observed a progressive decrease in the slopes and increase in the intercepts of the TA–S overtime due to the persistent process of TA enhancement. A weak seasonal pattern was identified, with warmer months presenting lower salinity and TA. Lower rates of TA increase were observed in high salinities (Skagerrak–Kattegat; +1.00 to +2.20 μmol kg−1 yr−1), intermediate trends in low salinities (Gulf of Bothnia; +3.28 to +3.57 μmol kg−1 yr−1), and maximal trends in the Central Baltic Sea (+3.70 to +4.57 μmol kg−1 yr−1) and Bornholm Basin (+4.82 to +5.32 μmol kg−1 yr−1). The increase in the intercept of the TA–S in the Gulf of Bothnia suggests a progressive increase in the external supply of TA, although lower than previously thought. The maximum trend in the Bornholm Basin suggests an increase in external supply from the Southern catchment and/or the accumulation of internal production. The positive TA–phosphorus correlations underscore a significant internal source. The TA increase amplifies the CO2 uptake by 1.8–7.8% during spring/summer and reduces the CO2 outgassing by 3.4–7.7% in autumn/winter. The TA enhancement has the potential to buffer CO2‐induced acidification by 39–60% by 2050.

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Sea surface circulation in the Baltic Sea: decomposed components and pattern recognition

Barzandeh,

Maljutenko,

Rikka

et al. 2024

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By decomposing the total sea surface current into its geostrophic and ageostrophic components, we examined the contribution of each to the long-term variability of the total sea surface current. Our findings demonstrate the importance of geostrophic currents in Baltic Sea gyre formations. Additionally, ageostrophic currents contribute significantly to the flow across the region. Quantifying the difference between total sea surface current fields has revealed two dominant general sea surface circulation patterns in the Baltic Sea, whose characteristics correspond to the monthly mean climatology of sea surface current fields in May and December. Subsequently, a machine learning technique was employed to effectively detect the types of sea surface circulation patterns using wind vectors and sea level anomaly fields. This underscored the combined influence of sea level anomaly-driven and wind-driven components in shaping surface current vectors in the Baltic Sea, consistent with geostrophic and ageostrophic decompositions.

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The Water Cycle of the Baltic Sea Region From GRACE/GRACE-FO Missions and ERA5 Data

Cited by 6 publications

References 60 publications

Observation of a moderate major Baltic Sea inflow in December 2023

Observation of a moderate major Baltic Sea inflow in December 2023

Increase in marginal sea alkalinity may impact air–sea carbon dioxide exchange and buffer acidification

Sea surface circulation in the Baltic Sea: decomposed components and pattern recognition

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