Holocene trends in the foraminifer record from the Norwegian Sea and the North Atlantic Ocean

Andersson, Carin; Pausata, Francesco S. R.; Jansen, Eystein; Risebrobakken, Bjørg; Telford, Richard J.

doi:10.5194/cp-6-179-2010

Cited by 80 publications

(92 citation statements)

References 55 publications

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“…Simulation 9kOG-GIS includes all presented forcings and still agrees to some extent to the proxy reconstructions, meaning that the results are more complete as compared to the other simulations. Regarding the foraminifera-based SSTs, our model shows that seasonal summer warming in the early Holocene is mainly active in the upper ∼ 100 m (not shown), in line with findings of Andersson et al (2010) for the mid-Holocene. Our model further shows that GIS melt affects only the uppermost 50 m of the water column (not shown).…”

Section: Comparison With Proxy-based Sstssupporting

confidence: 70%

“…Jansen et al (2008) suggest that the SST maximum recorded in proxy data above the seasonal thermocline (diatoms, alkenones) is forced by the summer insolation maximum and that deeper dwelling species (foraminifera and radiolarians) are not influenced. Andersson et al (2010) support this hypothesis in a comparison with climate model simulations of the 6 ka BP climate performed with the CCSM3 model. These model results suggest that seasonal summer warming, related to the orbitally forced summer insolation maximum, is restricted to the upper 30 m in the Nordic Seas during the early Holocene.…”

Section: Introductionsupporting

confidence: 57%

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The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

Blaschek¹,

Renssen²

2013

Clim. Past

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Abstract. The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene thermal maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveals a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS), as a remnant from the previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS) on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in an ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of the early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come.

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Section: Comparison With Proxy-based Sstssupporting

confidence: 70%

Section: Introductionsupporting

confidence: 57%

The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

Blaschek¹,

Renssen²

2013

Clim. Past

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“…Most marine records from the North Atlantic and the Nordic Seas indicate an early to mid-Holocene (∼10-8 ka) oceanic thermal optimum (e.g. Birks and Koç, 2002;Calvo et al, 2002;Hald et al, 2007;Bauch and Erlenkeuser, 2008;Andersson et al, 2010;Risebrobakken et al, 2011), in agreement with maximum boreal summer insolation values recorded at 11 ka (e.g. Berger and Loutre, 1991).…”

Section: A Govin Et Al: Early Last Interglacial Climate and Ice Shementioning

confidence: 59%

Persistent influence of ice sheet melting on high northern latitude climate during the early Last Interglacial

et al. 2012

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Abstract. Although the Last Interglacial (LIG) is often considered as a possible analogue for future climate in high latitudes, its precise climate evolution and associated causes remain uncertain. Here we compile high-resolution marine sediment records from the North Atlantic, Labrador Sea, Norwegian Sea and the Southern Ocean. We document a delay in the establishment of peak interglacial conditions in the North Atlantic, Labrador and Norwegian Seas as compared to the Southern Ocean. In particular, we observe a persistent iceberg melting at high northern latitudes at the beginning of the LIG. It is associated with (1) colder and fresher surfacewater conditions in the North Atlantic, Labrador and Norwegian Seas, and (2) a weaker ventilation of North Atlantic deep waters during the early LIG (129-125 ka) compared to the late LIG. Results from an ocean-atmosphere coupled model with insolation as a sole forcing for three key periods of the LIG show warmer North Atlantic surface waters and stronger Atlantic overturning during the early LIG (126 ka) than the late LIG (122 ka). Hence, insolation variations alone do not explain the delay in peak interglacial conditions observed at high northern latitudes. Additionally, we consider an idealized meltwater scenario at 126 ka where the freshwater input is interactively computed in response to the high boreal summer insolation. The model simulates colder, fresher North Atlantic surface waters and weaker Atlantic overturning during the early LIG (126 ka) compared to the late LIG (122 ka). This result suggests that both insolation and ice sheet melting have to be considered to reproduce the climatic pattern that we identify during the early LIG. Our modeldata comparison also reveals a number of limitations and reinforces the need for further detailed investigations using coupled climate-ice sheet models and transient simulations.

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“…This has been done, for example by Andersson et al (2010) who reconstructed 100-m SST. Reconstructions of subsurface conditions could be interpreted in much the same way as surface reconstructions, and could be used as a target for estimating climate sensitivity.…”

Section: Solutionsmentioning

confidence: 99%

Mismatch between the depth habitat of planktonic foraminifera and the calibration depth of SST transfer functions may bias reconstructions

Telford

Kučera

2013

Clim. Past

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Abstract. We demonstrate that the temperature signal in the planktonic foraminifera assemblage data from the North Atlantic typically does not originate from near-surface waters and argue that this has the potential to bias sea surface temperature reconstructions using transfer functions calibrated against near-surface temperatures if the thermal structure of the upper few hundred metres of ocean changes over time. CMIP5 climate models indicate that ocean thermal structure in the North Atlantic changed between the Last Glacial Maximum (LGM) and the pre-industrial (PI), with some regions, mainly in the tropics, of the LGM ocean lacking good thermal analogues in the PI. Transfer functions calibrated against different depths reconstruct a marked subsurface cooling in parts of the tropical North Atlantic during the last glacial, in contrast to previous studies that reconstruct only a modest cooling. These possible biases in temperature reconstructions may affect estimates of climate sensitivity based on the difference between LGM and pre-industrial climate. Quantifying these biases has the potential to alter our understanding of LGM climate and improve estimates of climate sensitivity.

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Holocene trends in the foraminifer record from the Norwegian Sea and the North Atlantic Ocean

Cited by 80 publications

References 55 publications

The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

Persistent influence of ice sheet melting on high northern latitude climate during the early Last Interglacial

Mismatch between the depth habitat of planktonic foraminifera and the calibration depth of SST transfer functions may bias reconstructions

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