Is ‘deep-water formation’ in the Baltic Sea a key to understanding seabed dynamics and ventilation changes over the past 7,000 years?

Moros, Matthias; Kotilainen, Aarno; Snowball, Ian; Neumann, Thomas; Perner, Kerstin; Meier, H. E. Markus; Leipe, Thomas; Zillén, Lovisa; Damsté, Jaap S. Sinninghe; Schneider, Ralph R

doi:10.1016/j.quaint.2020.03.031

Cited by 24 publications

(33 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Despite the appearance of the additional deeper inflow of bottom water from the Gulf of Finland in the BRP bottom experiment, a contribution to the Landsort Deep bottom waters from the northern sub‐basins, as hypothesized by Moros et al. (2020), is not found. For this to be possible, two requirements must be met: first, a water mass with a density high enough to be layered into the central Baltic Sea bottom waters must be formed in the sub‐basins, and second, the circulation conditions must be such that this water mass is transported into the central Baltic Sea.…”

Section: Resultsmentioning

confidence: 66%

“…The geological findings described in Moros et al. (2020) suggest that during cold periods, not only local wintertime convection is taking place, but the deep water formed in the northern sub‐basins is further transported into the deep parts of the northern central Baltic Sea. By evaluating the temporal evolution of tracer concentrations, we can follow the pathways of the winter surface water of the three sub‐basins.…”

Section: Resultsmentioning

confidence: 96%

“…Those bottom currents could be too small‐scaled to be resolved in a typical regional ocean circulation model but would imprint to the seafloor morphology, for instance as erosion channels or drift deposits as found by Moros et al. (2020) and also in the high‐resolution multibeam data from R/V Electra presented in Jakobsson et al. (2019).…”

Section: Discussionmentioning

confidence: 99%

“…It is conceivable that in reality, small-scale bottom currents that are highly dependent on topographic features can form and exchange deep water between the Gulf of Bothnia and the central Baltic Sea. Those bottom currents could be too small-scaled to be resolved in a typical regional ocean circulation model but would imprint to the seafloor morphology, for instance as erosion channels or drift deposits as found by Moros et al (2020) and also in the high-resolution multibeam data from R/V Electra presented in Jakobsson et al (2019).…”

Section: Bathymetry and Sill Depthsmentioning

confidence: 99%

“…(2020) suggest wintertime deep water formation as a second process that has contributed to sediment re‐deposition in and bottom water ventilation of the northern and central Baltic Sea during preceding cold phases like the Little Ice Age (LIA). This hypothesis is based on evidence from numerous sediment cores (e.g., irregularities in chronologies based on radiocarbon dating results) and seismoacoustic profiles (examples are shown in the supporting information), indicating that during cold phases, local convection resulted in deep water formation and further produced strong southward‐directed bottom currents causing a lateral sediment influx from the northern sub‐basins to the northern Baltic proper and Landsort Deep (Moros et al., 2020). Furthermore, measurements of oxygen concentration indicate that bottom water ventilation through wintertime deep water formation might have also occurred during severe winters in the current climate state (see supporting information).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Revisiting the Role of Convective Deep Water Formation in Northern Baltic Sea Bottom Water Renewal

et al. 2020

Self Cite

View full text Add to dashboard Cite

Deep water renewal and ventilation of the Baltic Sea is commonly considered to occur solely via saltwater inflows from the North Sea. However, recent analysis of geophysical and sediment proxy data suggests convective deep water formation during wintertime as a second process that has contributed to the ventilation of the northern and central Baltic Sea bottom waters during cold climate periods. Here, we investigate the role of deep water formation in the northern Baltic Sea in a regional ocean circulation model. Selecting the particularly cold winter 1986/1987 as a reference period, we perform sensitivity experiments in which the atmospheric temperature forcing is changed and/or localized brine rejection on subgrid scales is accounted for through a parameterization. We study the sinking and circulation of water masses via passive tracers introduced into the model. Generally, our model results support the established view that convective deep water formation does not play a major role in Baltic Sea deep water renewal. While a reduction of air temperatures does not qualitatively change the sinking and circulation of water masses in our experiments, brine rejection could potentially lead to localized deep water formation. However, the impact is too weak to possibly change the large-scale deep water exchange between the Baltic proper and the northern Baltic sub-basins. Although being in line with established knowledge, through consideration of the model limitations, our results provide insights on how and under which circumstances convective deep water formation could potentially have occurred during cold climate periods. Plain Language Summary The transport of oxygen-rich water into the deep parts of the Baltic Sea is of crucial importance for the ecosystem, as under low-oxygen conditions (hypoxia), most organisms cannot survive and so-called dead zones are formed. The ventilation of Baltic Sea bottom waters is commonly considered to occur solely through inflows of dense, oxygenated water from the North Sea. However, recent analysis of sediment cores and geophysical data suggests the contribution of a second process during cold climate periods: convective deep water formation. This process is initiated through surface cooling or an increase of surface water salinity during sea ice formation (brine rejection) in the winter season. Here, we investigate the role of deep water formation in the northern Baltic Sea in a regional ocean circulation model. We test the influence of reduced air temperatures and consideration of strong, localized brine rejection by performing sensitivity experiments. Generally, our model results do not support the hypothesis of convective deep water formation contributing to the renewal of Baltic Sea bottom waters, but are in line with the established view. Nevertheless, our results provide insights on how and under which circumstances convective deep water formation could potentially have occurred during cold climate periods.

show abstract

Section: Resultsmentioning

confidence: 66%

Section: Resultsmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Bathymetry and Sill Depthsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Revisiting the Role of Convective Deep Water Formation in Northern Baltic Sea Bottom Water Renewal

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

Glimpse of past dynamics: A new set of phytoplankton primers for sedaDNA

Romahn,

Baranski,

Schmidt

et al. 2024

Environmental DNA

View full text Add to dashboard Cite

Sedimentary ancient DNA (sedaDNA) offers an important opportunity for investigating long‐term community dynamics. Nevertheless, sedaDNA is challenging since DNA is degraded and fragmented over time. Of particular interest for such sedaDNA studies are phytoplankton communities, which are sensitive environmental indicators and important producers in aquatic systems. So far, only a few suitable metabarcoding primers for sedaDNA targeting phytoplankton exist. In this study, we introduce new metabarcoding primers targeting cyanobacteria and dinoflagellates. They amplify short, ~200‐bp ribosomal 16S and 18S DNA fragments. We compared these primers against published ones, uncovering distinct communities captured by different primer sets. The newly designed dinoflagellate and cyanobacterial primers revealed unique sets of amplicon sequence variants (ASVs) compared to published primers, highlighting the impact of primer choice on describing community composition. We also explored the effect of amplicon length on metabarcoding success over a sample age. Observed trends suggest that amplification success decreases with longer amplicons, probably as a result of DNA degradation in older sediment samples. Lastly, strong DNA preservation challenges emerged in sediment samples older than 7000 BP, corresponding with oxic phases of the Baltic Sea bottom water. This emphasizes the importance of age, sediment type, and preservation conditions when interpreting sedaDNA results. Despite limitations in temporal resolution, the study shows that sedaDNA‐based fluctuations in the phytoplankton community are consistent with well‐known environmental stages. More research is necessary to understand (1) DNA preservation and its impact on reconstructed communities and (2) impact of abiotic conditions on phytoplankton communities.

show abstract