Reconstruction of hydrographic changes in the southern Norwegian Sea during the past 135 kyr and the impact of different foraminiferal Mg/Ca cleaning protocols

Ezat, Mohamed; Rasmussen, Tine L.; Groeneveld, Jeroen

doi:10.1002/2016gc006325

Cited by 17 publications

(24 citation statements)

References 104 publications

(225 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[] and Ezat et al . [] used the large and abrupt increase in δ 18 O in benthic (~1‰) and planktic (~0.5‰) foraminifera at 197 cm core depth (Figure ) as a marker of the onset of IS 1. The increase in benthic foraminiferal δ 18 O is thought to mark the end of HS1 and the onset of deep convection similar to today [e.g., Rasmussen and Thomsen , ; Meland et al ., ].…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species‐specific benthic foraminiferal ¹⁴C dates

et al. 2017

Self Cite

View full text Add to dashboard Cite

Formation of deep water in the high‐latitude North Atlantic is important for the global meridional ocean circulation, and its variability in the past may have played an important role in regional and global climate change. Here we study ocean circulation associated with the last (de)glacial period, using water‐column radiocarbon age reconstructions in the Faroe‐Shetland Channel, southeastern Norwegian Sea, and from the Iceland Basin, central North Atlantic. The presence of tephra layer Faroe Marine Ash Zone II, dated to ~26.7 ka, enables us to determine that the middepth (1179 m water depth) and shallow subsurface reservoir ages were ~1500 and 1100 14C years, respectively, older during the late glacial period compared to modern, suggesting substantial suppression of the overturning circulation in the Nordic Seas. During the late Last Glacial Maximum and the onset of deglaciation (~20–18 ka), Nordic Seas overflow was weak but active. During the early deglaciation (~17.5–14.5 ka), our data reveal large differences between 14C ventilation ages that are derived from dating different benthic foraminiferal species: Pyrgo and other miliolid species yield ventilation ages >6000 14C years, while all other species reveal ventilation ages <2000 14C years. These data either suggest subcentennial, regional, circulation changes or that miliolid‐based 14C ages are biased due to taphonomic or vital processes. Implications of each interpretation are discussed. Regardless of this “enigma,” the onset of the Bølling‐Allerød interstadial (14.5 ka) is clearly marked by an increase in middepth Nordic Seas ventilation and the renewal of a stronger overflow.

show abstract

Section: Methodsmentioning

confidence: 99%

“…In addition, the start of the deglacial δ 18 O decrease in N . pachyderma according to our age model is at ~17.5 ka [ Hoff et al ., ; Ezat et al ., ], while it was dated ~16.5 ka according to the age model of Thornalley et al . [].…”

Section: Methodsmentioning

confidence: 99%

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species‐specific benthic foraminiferal ¹⁴C dates

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

“…Due to poor preservation, not enough specimens were present for the analysis of Mg / Ca ratios in depths < 5 and > 30 m c.d. Trace metal / Ca in foraminifera from the Nordic and Baltic seas has been shown to be occasionally affected by diagenetic coatings (Groeneveld and Filipsson, 2013;Ezat et al, 2016). Standard cleaning procedures for trace metal / Ca in foraminifera after clay removal either involve only an oxidation step to remove organic matter (Barker et al, 2003) or also include a reduction step before the oxidation (Martin and Lea, 2002) to remove (oxy)hydroxide coatings.…”

Section: Trace Metal / Calcium In Foraminiferamentioning

confidence: 99%

Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059)

et al. 2017

Self Cite

View full text Add to dashboard Cite

Abstract. Sediment records recovered from the Baltic Sea during Integrated Ocean Drilling Program Expedition 347 provide a unique opportunity to study paleoenvironmental and climate change in central and northern Europe. Such studies contribute to a better understanding of how environmental parameters change in continental shelf seas and enclosed basins. Here we present a multi-proxy-based reconstruction of paleotemperature (both marine and terrestrial), paleosalinity, and paleoecosystem changes from the Little Belt (Site M0059) over the past ∼ 8000 years and evaluate the applicability of inorganic-and organic-based proxies in this particular setting.All salinity proxies (diatoms, aquatic palynomorphs, ostracods, diol index) show that lacustrine conditions occurred in the Little Belt until ∼ 7400 cal yr BP. A connection to the Kattegat at this time can thus be excluded, but a direct connection to the Baltic Proper may have existed. The transition to the brackish-marine conditions of the Littorina Sea stage (more saline and warmer) occurred within ∼ 200 years when the connection to the Kattegat became established after ∼ 7400 cal yr BP. The different salinity proxies used here generally show similar trends in relative changes in salinity, but often do not allow quantitative estimates of salinity.Published by Copernicus Publications on behalf of the European Geosciences Union. U. Kotthoff et al.: Little Belt multi-proxy comparisonThe reconstruction of water temperatures is associated with particularly large uncertainties and variations in absolute values by up to 8 • C for bottom waters and up to 16 • C for surface waters. Concerning the reconstruction of temperature using foraminiferal Mg / Ca ratios, contamination by authigenic coatings in the deeper intervals may have led to an overestimation of temperatures. Differences in results based on the lipid paleothermometers (long chain diol index and TEX L 86 ) can partly be explained by the application of modern-day proxy calibrations to intervals that experienced significant changes in depositional settings: in the case of our study, the change from freshwater to marine conditions. Our study shows that particular caution has to be taken when applying and interpreting proxies in coastal environments and marginal seas, where water mass conditions can experience more rapid and larger changes than in open ocean settings. Approaches using a multitude of independent proxies may thus allow a more robust paleoenvironmental assessment.

show abstract

“…Our results suggest that the Norwegian Sea remained a CO 2 sink during most of the past 135 kyr, but during the latest parts of HS1, HS4 and HS11 the area acted as a source of CO 2 to the atmosphere. To elucidate the causes of these variations in seawater carbonate chemistry, we compare our results with previously published reconstructions of temperature 14 15 , sea-ice cover, input of terrestrial organic matter and primary productivity 16 .…”

mentioning

confidence: 99%

Episodic release of CO2 from the high-latitude North Atlantic Ocean during the last 135 kyr

et al. 2017

Self Cite

View full text Add to dashboard Cite

Antarctic ice cores document glacial-interglacial and millennial-scale variability in atmospheric pCO2 over the past 800 kyr. The ocean, as the largest active carbon reservoir on this timescale, is thought to have played a dominant role in these pCO2 fluctuations, but it remains unclear how and where in the ocean CO2 was stored during glaciations and released during (de)glacial millennial-scale climate events. The evolution of surface ocean pCO2 in key locations can therefore provide important clues for understanding the ocean's role in Pleistocene carbon cycling. Here we present a 135-kyr record of shallow subsurface pCO2 and nutrient levels from the Norwegian Sea, an area of intense CO2 uptake from the atmosphere today. Our results suggest that the Norwegian Sea probably acted as a CO2 source towards the end of Heinrich stadials HS1, HS4 and HS11, and may have contributed to the increase in atmospheric pCO2 at these times.

show abstract

Reconstruction of hydrographic changes in the southern Norwegian Sea during the past 135 kyr and the impact of different foraminiferal Mg/Ca cleaning protocols

Cited by 17 publications

References 104 publications

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species‐specific benthic foraminiferal ¹⁴C dates

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species‐specific benthic foraminiferal ¹⁴C dates

Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059)

Episodic release of CO2 from the high-latitude North Atlantic Ocean during the last 135 kyr

Contact Info

Product

Resources

About

Reconstruction of hydrographic changes in the southern Norwegian Sea during the past 135 kyr and the impact of different foraminiferal Mg/Ca cleaning protocols

Cited by 17 publications

References 104 publications

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species‐specific benthic foraminiferal 14C dates

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species‐specific benthic foraminiferal 14C dates

Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059)

Episodic release of CO2 from the high-latitude North Atlantic Ocean during the last 135 kyr

Contact Info

Product

Resources

About

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species‐specific benthic foraminiferal ¹⁴C dates

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species‐specific benthic foraminiferal ¹⁴C dates