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Papers by Marie-Louise Siggaard-Andersen

Climate of the Past Discussions, 2007

SSTs were obtained from the unsaturation ratio of C37 alkenones (𝑈37 𝐾′ = C37:2/(C37:2 + C37:3) a... more SSTs were obtained from the unsaturation ratio of C37 alkenones (𝑈37 𝐾′ = C37:2/(C37:2 + C37:3) and the BAYSPLINE calibration.

The North-GRIP ice core provides continuous records of sea salt and mineral dust aerosols from th... more The North-GRIP ice core provides continuous records of sea salt and mineral dust aerosols from the last glacial period. A large number of soluble ions were analysed by ion chromatography and have opened up for new possibilities looking into details in the relationship between ion composition and climate conditions. Changes in ion compositions seem to be related to changes in particle size distributions as an effect of fractionation during long-range atmospheric transport.Analysis of ion-compositions in the North-GRIP ice core suggests that long-range atmospheric transport patterns remained nearly unchanged during the Dansgaard/Oeschger events and were constant through most of the last glacial period. However in sections of the early part of the last glacial period the analysis shows a prominently different pattern of ion composition. These differences are associated with differences in particle size distributions and indicate major differences in circulation patterns during the earl...

Sulphate aerosols are playing a major role in climate forcing in the present atmosphere and there... more Sulphate aerosols are playing a major role in climate forcing in the present atmosphere and therefore possibly also during other climatic stages. The deposition of sulphur-containing species onto polar ice sheets provides a tool for determining variations in the sulphur cycle in the past. Relatively short atmospheric residence times for sulphate aerosols cause spatial gradients and a high sensitivity to

High resolution aerosol data from Greenland NGRIP and NEEM ice cores. All data was measured using... more High resolution aerosol data from Greenland NGRIP and NEEM ice cores. All data was measured using continuous flow analysis with the Bern CFA system during the respective field campaigns. Data is provided at 1mm depth resolution and 10yr averages on the GICC05 age scale of the respective core

During the 2000 field season, chemical anaylses have been done using a Continuous Flow Analysis (... more During the 2000 field season, chemical anaylses have been done using a Continuous Flow Analysis (CFA) system at the North Greenland Ice Core Project (North GRIP) site (75.1°N, 42.3°W, accumulation rate 17 g cm-2 yr-1), resulting in high-resolution records for ammonium, calcium, sodium, nitrate, sulphate, formaldehyde, hydrogen peroxide, conductivity and dust. The resolution achieved ranges from approximately 0.2 yrs in

Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European... more Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European Project for Ice Coring in Antarctica) deep ice cores. The joint use of these records from opposite sides of the East Antarctic plateau allows for an estimate of changes in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosol source. The mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes in the glacial Patagonian dust source with three times higher dust fluxes in the Atlantic compared to the Indian Ocean sector of the Southern Ocean (SO). Using a simple conceptual transport model this indicates that transport can explain only 40% of the atmospheric dust concentration changes in Antarctica, while factor 5-10 changes occurred. Accordingly, the main cause for the strong glacial dust flux changes in Antarctica must lie in environmental changes in Patagonia. Dust emissions, hence environmental conditions in Patagonia, were very similar during the last two glacials and interglacials, respectively, despite 2-4 °C warmer temperatures recorded in Antarctica during the penultimate interglacial than today. 2-3 times higher sea salt fluxes found in both ice cores in the glacial compared to the Holocene are difficult to reconcile with a largely unchanged transport intensity and the distant open ocean source. The substantial glacial enhancements in sea salt aerosol fluxes can be readily explained assuming sea ice formation as the main sea salt aerosol source with a significantly larger expansion of (summer) sea ice in the Weddell Sea than in the Indian Ocean sector. During the penultimate interglacial, our sea salt records point to a 50% reduction of winter sea ice coverage compared to the Holocene both in the Indian and Atlantic Ocean sector of the SO. However, from 20 to 80 ka before present sea salt fluxes show only very subdued millennial changes despite pronounced temperature fluctuations, like [...]

During the 2000 field season at North GRIP (Greenland), high-resolution chemical analyses have be... more During the 2000 field season at North GRIP (Greenland), high-resolution chemical analyses have been done using the Bern Continuous Flow Analysis (CFA) system. Among other substances, sulphate SO_4{}2- has been recorded continuously over the last glacial period, i.e. from approximately 100 kyr to 9.5 kyr before present. The one-centimetre resolution of the record allows us to obtain a comprehensive list of potential volcanic sulphuric acid events from which a frequency distribution can be derived. Taking background sulphate into account, the events can be assigned to different strength categories. The record from North GRIP is then compared to other time series of volcanic activity, which allows us to distinguish regional, hemispheric or global events.

Journal of Geophysical Research, 2008

Journal of Geophysical Research, 2006

As part of the effort to create the new Greenland Ice Core Chronology 2005 (GICC05) a synchronize... more As part of the effort to create the new Greenland Ice Core Chronology 2005 (GICC05) a synchronized stratigraphical timescale for the Holocene parts of the DYE-3, Greenland Ice Core Project (GRIP), and North Greenland Ice Core Project (NGRIP) ice cores is made by using volcanic reference horizons in electrical conductivity measurements to match the cores. The main annual layer counting is carried out on the most suited records only, exploiting that the three ice cores have been drilled at locations with different climatic conditions and differences in ice flow. However, supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the validity of the match. After the verification, the main dating is transferred to all records using the volcanic reference horizons as tie points. An assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores. The data used for the main annual layer counting of the past 7900 years are the DYE-3, GRIP, and NGRIP stable isotope records. As the high accumulation rate at the DYE-3 drill site makes the seasonal cycle in the DYE-3 stable isotopes very resistant to firn diffusion, an effort has been made to extend the DYE-3 Holocene record. The new synchronized dating relies heavily on this record of $75,000 stable isotope samples. The dating of the early Holocene consists of an already established part of GICC05 for GRIP and NGRIP which has now been transferred to the DYE-3 core. GICC05 dates the Younger Dryas termination, as defined from deuterium excess, to 11,703 years before A. D. 2000 (b2k), 130 years earlier than the previous GRIP dating.

Earth-Science Reviews, 2022

This dataset includes the SST reconstruction, ice-rafted debris measurements, and age model of co... more This dataset includes the SST reconstruction, ice-rafted debris measurements, and age model of core FOX12-02R.In recent years, several large outlet glaciers in Greenland have lost their floating ice tongue, but little is known about their stability over longer time-scales. Here, we compile historical documents to demonstrate a major ice tongue collapse of Kangerlussuaq Glacier between 1932- 1933. This event resulted in nine kilometer retreat, which is more than during any of the glacier's recent major retreat events. Sediment cores from the fjord are used to reconstruct sea surface temperatures (SSTs) and to investigate a potential sedimentological trace of the collapse. Local SSTs increased during the 1920s, consistent with other regional air and ocean temperature records, suggesting a climatic trigger for the collapse. Fjord bathymetry played an important role too, as the (partially-) pinned ice tongue retreated off a submarine moraine during the event. This historical analogu...

Climate of the Past Discussions, 2007

SSTs were obtained from the unsaturation ratio of C37 alkenones (𝑈37 𝐾′ = C37:2/(C37:2 + C37:3) a... more SSTs were obtained from the unsaturation ratio of C37 alkenones (𝑈37 𝐾′ = C37:2/(C37:2 + C37:3) and the BAYSPLINE calibration.

The North-GRIP ice core provides continuous records of sea salt and mineral dust aerosols from th... more The North-GRIP ice core provides continuous records of sea salt and mineral dust aerosols from the last glacial period. A large number of soluble ions were analysed by ion chromatography and have opened up for new possibilities looking into details in the relationship between ion composition and climate conditions. Changes in ion compositions seem to be related to changes in particle size distributions as an effect of fractionation during long-range atmospheric transport.Analysis of ion-compositions in the North-GRIP ice core suggests that long-range atmospheric transport patterns remained nearly unchanged during the Dansgaard/Oeschger events and were constant through most of the last glacial period. However in sections of the early part of the last glacial period the analysis shows a prominently different pattern of ion composition. These differences are associated with differences in particle size distributions and indicate major differences in circulation patterns during the earl...

Sulphate aerosols are playing a major role in climate forcing in the present atmosphere and there... more Sulphate aerosols are playing a major role in climate forcing in the present atmosphere and therefore possibly also during other climatic stages. The deposition of sulphur-containing species onto polar ice sheets provides a tool for determining variations in the sulphur cycle in the past. Relatively short atmospheric residence times for sulphate aerosols cause spatial gradients and a high sensitivity to

High resolution aerosol data from Greenland NGRIP and NEEM ice cores. All data was measured using... more High resolution aerosol data from Greenland NGRIP and NEEM ice cores. All data was measured using continuous flow analysis with the Bern CFA system during the respective field campaigns. Data is provided at 1mm depth resolution and 10yr averages on the GICC05 age scale of the respective core

During the 2000 field season, chemical anaylses have been done using a Continuous Flow Analysis (... more During the 2000 field season, chemical anaylses have been done using a Continuous Flow Analysis (CFA) system at the North Greenland Ice Core Project (North GRIP) site (75.1°N, 42.3°W, accumulation rate 17 g cm-2 yr-1), resulting in high-resolution records for ammonium, calcium, sodium, nitrate, sulphate, formaldehyde, hydrogen peroxide, conductivity and dust. The resolution achieved ranges from approximately 0.2 yrs in

Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European... more Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European Project for Ice Coring in Antarctica) deep ice cores. The joint use of these records from opposite sides of the East Antarctic plateau allows for an estimate of changes in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosol source. The mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes in the glacial Patagonian dust source with three times higher dust fluxes in the Atlantic compared to the Indian Ocean sector of the Southern Ocean (SO). Using a simple conceptual transport model this indicates that transport can explain only 40% of the atmospheric dust concentration changes in Antarctica, while factor 5-10 changes occurred. Accordingly, the main cause for the strong glacial dust flux changes in Antarctica must lie in environmental changes in Patagonia. Dust emissions, hence environmental conditions in Patagonia, were very similar during the last two glacials and interglacials, respectively, despite 2-4 °C warmer temperatures recorded in Antarctica during the penultimate interglacial than today. 2-3 times higher sea salt fluxes found in both ice cores in the glacial compared to the Holocene are difficult to reconcile with a largely unchanged transport intensity and the distant open ocean source. The substantial glacial enhancements in sea salt aerosol fluxes can be readily explained assuming sea ice formation as the main sea salt aerosol source with a significantly larger expansion of (summer) sea ice in the Weddell Sea than in the Indian Ocean sector. During the penultimate interglacial, our sea salt records point to a 50% reduction of winter sea ice coverage compared to the Holocene both in the Indian and Atlantic Ocean sector of the SO. However, from 20 to 80 ka before present sea salt fluxes show only very subdued millennial changes despite pronounced temperature fluctuations, like [...]

During the 2000 field season at North GRIP (Greenland), high-resolution chemical analyses have be... more During the 2000 field season at North GRIP (Greenland), high-resolution chemical analyses have been done using the Bern Continuous Flow Analysis (CFA) system. Among other substances, sulphate SO_4{}2- has been recorded continuously over the last glacial period, i.e. from approximately 100 kyr to 9.5 kyr before present. The one-centimetre resolution of the record allows us to obtain a comprehensive list of potential volcanic sulphuric acid events from which a frequency distribution can be derived. Taking background sulphate into account, the events can be assigned to different strength categories. The record from North GRIP is then compared to other time series of volcanic activity, which allows us to distinguish regional, hemispheric or global events.

Journal of Geophysical Research, 2008

Journal of Geophysical Research, 2006

As part of the effort to create the new Greenland Ice Core Chronology 2005 (GICC05) a synchronize... more As part of the effort to create the new Greenland Ice Core Chronology 2005 (GICC05) a synchronized stratigraphical timescale for the Holocene parts of the DYE-3, Greenland Ice Core Project (GRIP), and North Greenland Ice Core Project (NGRIP) ice cores is made by using volcanic reference horizons in electrical conductivity measurements to match the cores. The main annual layer counting is carried out on the most suited records only, exploiting that the three ice cores have been drilled at locations with different climatic conditions and differences in ice flow. However, supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the validity of the match. After the verification, the main dating is transferred to all records using the volcanic reference horizons as tie points. An assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores. The data used for the main annual layer counting of the past 7900 years are the DYE-3, GRIP, and NGRIP stable isotope records. As the high accumulation rate at the DYE-3 drill site makes the seasonal cycle in the DYE-3 stable isotopes very resistant to firn diffusion, an effort has been made to extend the DYE-3 Holocene record. The new synchronized dating relies heavily on this record of $75,000 stable isotope samples. The dating of the early Holocene consists of an already established part of GICC05 for GRIP and NGRIP which has now been transferred to the DYE-3 core. GICC05 dates the Younger Dryas termination, as defined from deuterium excess, to 11,703 years before A. D. 2000 (b2k), 130 years earlier than the previous GRIP dating.

Earth-Science Reviews, 2022

This dataset includes the SST reconstruction, ice-rafted debris measurements, and age model of co... more This dataset includes the SST reconstruction, ice-rafted debris measurements, and age model of core FOX12-02R.In recent years, several large outlet glaciers in Greenland have lost their floating ice tongue, but little is known about their stability over longer time-scales. Here, we compile historical documents to demonstrate a major ice tongue collapse of Kangerlussuaq Glacier between 1932- 1933. This event resulted in nine kilometer retreat, which is more than during any of the glacier's recent major retreat events. Sediment cores from the fjord are used to reconstruct sea surface temperatures (SSTs) and to investigate a potential sedimentological trace of the collapse. Local SSTs increased during the 1920s, consistent with other regional air and ocean temperature records, suggesting a climatic trigger for the collapse. Fjord bathymetry played an important role too, as the (partially-) pinned ice tongue retreated off a submarine moraine during the event. This historical analogu...