Baltic Sea Hits Record Low Water Level Amid Persistent Easterly Winds

The Baltic Sea has recorded its lowest water volume since systematic observations began in 1886, a phenomenon attributed to sustained easterly winds since January 2026. This persistent weather pattern has forced significant volumes of water westward out through the Danish straits, including the Belt Sea, into the North Sea. The Leibniz Institute for Baltic Sea Research Warnemünde (IOW) has initiated a 49-day monitoring campaign to assess the ecological consequences of this rare oceanographic event.

As of February 5, 2026, the average sea level deficit surpassed 67.4 centimeters below the long-term mean, equating to an estimated loss of approximately 275 cubic kilometers of water from the basin. This level of reduction is historically significant; in the 140-year measurement record, only five other years have registered levels exceeding 60 centimeters below the norm. The Swedish Landsort-Norra gauge, which has provided continuous data since 1886, confirmed these record lows. The meteorological driver is a sustained high-pressure system, potentially originating from Siberia, which has blocked the typical approach of warmer, wetter cyclones from the west, diverting them toward Southern Europe.

Scientists suggest this wind-driven water displacement creates conditions conducive to a Major Baltic Inflow (MBI) from the North Sea. MBIs are crucial natural events, serving as the sole mechanism for reoxygenating the deep, saline waters of the central Baltic basins. These inflows introduce dense, cold, oxygen-rich water along the seabed, which displaces stagnant, oxygen-depleted water below the halocline. Such replenishment is vital for mitigating existing low-oxygen zones and improving reproductive conditions for species like cod, thereby enhancing overall biodiversity.

The Leibniz Institute for Baltic Sea Research Warnemünde has updated its time series for MBIs, indicating cyclical variations in intensity occurring roughly every 30 years, contrary to earlier data suggesting a decline. The last notable event, a medium-sized MBI, occurred in December 2023, providing temporary improvement in the southern Baltic Sea. Given the Baltic Sea’s unique, semi-enclosed geography and low salinity—roughly one-tenth that of the open ocean—water replacement is a slow process, often taking 20 to 30 years. The current record low water mark establishes a starting point for a potentially significant ecological rejuvenation following the anticipated influx of colder, saltier water.