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Andrén, Thomas; Andrén, Elinor; Zhang, Rui

doi:10.2204/iodp.pr.347.2014

Cited by 4 publications

(2 citation statements)

References 95 publications

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“…Our microanalysis results show that the Mn carbonate enrichments at site LL19 are highly laminar in character, implying rapid precipitation at or near the sediment-water interface. Furthermore, these Mn carbonate enrichments occur independently of enrichments in Mo and S. Sedimentary Mo can be used as a proxy for sulfidic conditions close to the sediment-water interface, due to the conversion of seawater oxymolybdate to particle-reactive thiomolybdate in the presence of hydrogen sulfide (Erickson and Helz, 2000). Although the ultimate burial phase of Mo in sulfidic sediments is still debated (e.g.…”

Section: Manganese Sequestration In the Anoxic Basinsmentioning

confidence: 99%

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Are recent changes in sediment manganese sequestration in the euxinic basins of the Baltic Sea linked to the expansion of hypoxia?

Lenz¹,

Jilbert²,

Conley³

et al. 2014

Preprint

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Abstract. Expanding hypoxia in the Baltic Sea over the past century has led to anoxic and sulfidic (euxinic) deep basins that are only periodically ventilated by inflows of oxygenated waters from the North Sea. In this study, we investigate the consequences of the expanding hypoxia for manganese (Mn) burial in the Baltic Sea using a combination of pore water and sediment analyses of well-dated sediment cores from 8 locations. Diffusive fluxes of dissolved Mn from sediments to overlying waters at oxic and hypoxic sites are in line with an active release of Mn from these areas. However, this flux of Mn is only small when compared to the large pool of Mn already present in the hypoxic and anoxic water column. Our results highlight two modes of Mn carbonate formation in sediments of the deep basins. In the Gotland Deep area, Mn carbonates likely form from Mn oxides that are precipitated from the water column directly following North Sea inflows. In the Landsort Deep, in contrast, Mn carbonate and Mn sulfide layers form independent of inflow events, with pore water Mn produced in deeper layers of the sediment acting as a key Mn source. While formation of Mn enrichments in the Landsort Deep continues to the present, this does not hold for the Gotland Deep area. Here, increased euxinia, as evident from measured bottom water sulfide concentrations and elevated sediment molybdenum (Mo), goes hand in hand with a decline in sediment Mn and recent inflows of oxygenated water (since ca. 1995) are no longer consistently recorded as Mn carbonate layers. We postulate that the reduction of Mn oxides by hydrogen sulfide following inflows has become so rapid that Mn2+ is released to the water column before Mn carbonates can form. Our results have important implications for the use of Mn carbonate enrichments as a redox proxy in marine systems.

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Section: Manganese Sequestration In the Anoxic Basinsmentioning

confidence: 99%

“…1997) into the Baltic Sea. The event in 1993 was one of the strongest in the last 60 years (Matthäus et al, 2008) and the inflow of 2003 (Feistel et al, 2003) was weaker but still significant enough to reoxygenate the bottom water of the deep basins (Fig. 7).…”

Section: Changes In Mn Burial Linked To Expanding Hypoxiamentioning

confidence: 99%

Are recent changes in sediment manganese sequestration in the euxinic basins of the Baltic Sea linked to the expansion of hypoxia?

Lenz¹,

Jilbert²,

Conley³

et al. 2014

Preprint

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Holocene stratigraphy of the Ångermanälven River estuary, Bothnian Sea

et al. 2016

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Salinity variations in restricted basins like the Baltic Sea can alter their vulnerability to hypoxia (i.e., bottom water oxygen concentrations <2 mg/l) and can affect the burial of phosphorus (P), a key nutrient for marine organisms. We combine porewater and solid-phase geochemistry, micro-analysis of sieved sediments (including XRD and synchrotron-based XAS), and foraminiferal δ 18 O and δ 13 C analyses to reconstruct the bottom water salinity, redox conditions , and P burial in the Ångermanälven estuary, Bothnian Sea. Our sediment records were retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. We demonstrate that bottom waters in the Ångermanälven estuary became an-oxic upon the intrusion of seawater in the early Holocene, like in the central Bothnian Sea. The subsequent refreshening and reoxygenation, which was caused by gradual isostatic uplift, promoted P burial in the sediment in the form of Mn-rich vivianite. Vivianite authigenesis in the surface sediments of the more isolated part of the estuary ultimately ceased, likely due to continued refreshening and an associated decline in productivity and P supply to the sediment. The observed shifts in environmental conditions also created conditions for post-depositional formation of authigenic vivianite, and possibly apatite formation, at ∼8 m composite depth. These salinity-related changes in redox conditions and P burial are highly relevant in light of current climate change. The results specifically highlight that increased freshwater input linked to global warming may enhance coastal P retention, thereby contributing to oligotrophication in both coastal and adjacent open waters.

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Deglaciation dynamics of the Fennoscandian Ice Sheet in the Kattegat, the gateway between the North Sea and the Baltic Sea Basin

Hyttinen

Krupinski

Bennike

et al. 2020

Boreas

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This paper presents an age–depth model based on an ultra‐high‐resolution, 80‐m‐thick sedimentary succession from a marine continental shelf basin, the Kattegat. This is an area of dynamic deglaciation of the Fennoscandian Ice Sheet during the Late Pleistocene. The Kattegat is also a transitional area between the saline North Sea and the brackish Baltic Sea. As such, it records general development of currents and exchange between these two systems. Data for the succession were provided through the Integrated Ocean Drilling Program Site M0060. The site indicates onset of deglaciation at c. 18 ka BP and relatively continuous sedimentation until 13 ka BP. At this point, sediments record a hiatus until c. 9–7 ka BP. The uppermost sedimentary unit contains redeposited material, but it is estimated to represent only the last c. 9–7 ka BP. The age–depth model is based on 17 select, radiocarbon‐dated samples and is integrated with a set of physical and chemical proxies. The integrated records provide novel constraints on the timing of major palaeoenvironmental changes, such as the transition from glaciomarine proximal to glaciomarine distal and marine conditions, and their connections to known major events and processes in the region and the North Atlantic. Depositional evidence specifically documents connections between the Fennoscandian Ice Sheet behaviour and atmospheric and oceanic warming. Glacial retreat may have also depended on topographic factors such as changes in basin width and depth, linked to relative sea level changes and land uplift. The results indicate an early response of the Fennoscandian Ice Sheet to changing climate, and the ice sheet's possible influence on oceanic circulation during the Late Pleistocene deglaciation.

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Cited by 4 publications

References 95 publications

Are recent changes in sediment manganese sequestration in the euxinic basins of the Baltic Sea linked to the expansion of hypoxia?

Are recent changes in sediment manganese sequestration in the euxinic basins of the Baltic Sea linked to the expansion of hypoxia?

Holocene stratigraphy of the Ångermanälven River estuary, Bothnian Sea

Deglaciation dynamics of the Fennoscandian Ice Sheet in the Kattegat, the gateway between the North Sea and the Baltic Sea Basin

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