Gerrit Lohmann - Alfred Wegener Institute for Polar and Marine Research (original) (raw)
Papers by Gerrit Lohmann
Geophysical Research Letters, Jul 20, 2018
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as
Tellus A, Aug 1, 2008
Globally forced model simulations with an atmospheric general circulation model of intermediate c... more Globally forced model simulations with an atmospheric general circulation model of intermediate complexity reveal surface air temperature (SAT) and sea level pressure (SLP) variations at multidecadal time scales. In order to separate the influence of individual ocean basins on the North Atlantic multidecadal variability, we force our model with observed SST data for the period 1856-2000 for Atlantic and Pacific Oceans, separately, while outside the atmosphere is coupled with the ocean via a mixed layer slab model. The experiments indicate the Atlantic Ocean as a principal driver of North Atlantic multidecadal variability, with SAT and SLP highly in phase in the North Atlantic at about 60-70 years time scale. The Pacific impact is associated to longer period variations in the SLP field over the North Atlantic. We suggest that two distinct physical modes of multidecadal climate variability exist, one of about 70 years possibly linked with the Atlantic thermohaline circulation, the other linked with the Pacific Ocean and connected to the Atlantic Ocean via Pacific-North America teleconnections. The latter has a time scale of about 80-100 years.
Paleoceanography and paleoclimatology, Feb 1, 2018
The last interglacial (LIG; Marine Isotope Substage 5e, ~127-117 ka) experienced globally warmer ... more The last interglacial (LIG; Marine Isotope Substage 5e, ~127-117 ka) experienced globally warmer than modern temperatures; however, profound differences in regional climate occurred that are relevant to the assessment of future climate change scenarios. Tropical Atlantic sea surface temperature (SST) and hydrology are intrinsic to the spatiotemporal evolution of past and future climate. We present eight monthly resolved coral Sr/Ca and δ 18 O records (130-118 ka) to reconstruct mean western tropical Atlantic SST and seawater δ 18 O changes during the LIG. Cooler and fresher than modern surface waters are indicated for the middle of the LIG at ~126 ka. This was followed by a rapid transition to modern-like SSTs and salinities that characterized the remaining part of the LIG. Our results, which account for differences found among corals, proxies, and SST calibration uncertainties, agree with western tropical Atlantic sediment records. Together, they suggest that an oceanic regime existed that differed from today.
EGU General Assembly Conference Abstracts, Apr 1, 2018
Age and alkenone-derived Holocene sea-surface temperature records of sediment core TY93-905
Age and alkenone-derived Holocene sea-surface temperature records of sediment core SSDP-102
Age and alkenone-derived Holocene sea-surface temperature records of sediment core GeoB5901-2
Ras Umm Sidd bimonthly δ¹⁸O and Sr/Ca data of coral core/colony RUS-95
Ras Umm Sidd bimonthly δ¹⁸O and Sr/Ca data and annual d18O, Sr/Ca, reconstructed Sr/Ca temperature and reconstructed d18O seawater data of coral core/colony RUS-95
The climate of the Sahara and Arabian deserts during the Little Ice Age is not well known, due to... more The climate of the Sahara and Arabian deserts during the Little Ice Age is not well known, due to a lack of annually resolved natural and documentary archives. We present an annual reconstruction of temperature and aridity derived from Sr/Ca and oxygen isotopes in a coral of the desert-surrounded northern Red Sea. Our data indicate that the eastern Sahara and Arabian Desert did not experience pronounced cooling during the late Little Ice Age (~1750-1850), but suggest an even more arid mean climate than in the following ~150 years. The mild temperatures are broadly in line with predominantly negative phases of the North Atlantic Oscillation during the Little Ice Age. The more arid climate is best explained by meridional advection of dry continental air from Eurasia. We find evidence for an abrupt termination of the more arid climate after 1850, coincident with a reorganization of the atmospheric circulation over Europe.
(Figure 2) Monthly interpolated coral d18O and d18Oseawater record from Bonaire coral BON-24-AII.2, 125.5 ka
Pages (Bern), Oct 1, 2004
Monthly Bonaire coral δ¹⁸O and d18Oseawater from the last interglacial, 120.5 -129.7 ka ago
The seasonality of hydroclimate during past periods of warmer than modern global temperatures is ... more The seasonality of hydroclimate during past periods of warmer than modern global temperatures is a critical component for understanding future climate change scenarios. Although partially analogous to these scenarios, the last interglacial (LIG, Marine Isotope Stage 5e, ~127-117 ka) is a popular test-bed. We present coral d18O monthly resolved records from multiple Bonaire (southern Caribbean) fossil corals (Diploria strigosa) that date to between 130 and 118 ka. These records represent up to 37 years and cover a total of 105 years, offering insights into the seasonality and characteristics of LIG tropical Atlantic hydroclimate. Our coral d18O records and available coral Sr/Ca- sea surface temperature (SST) records reveal new insights into the variable relationship between the seasonality of tropical Atlantic seawater d18O (d18Oseawater) and SST. Coral d18O seasonality is found to coevolve with SST and insolation seasonality throughout the LIG, culminating in significantly higher than modern values at 124 and 126 ka. At 124 ka, we reconstruct a 2-month lead of the coral d18O vs. the Sr/Ca-SST annual cycle and increased d18Oseawater seasonality. A fully-coupled climate model simulates a concomitant increase of southern Caribbean Sea summer precipitation and depletion of summer d18Oseawater. LIG regional hydroclimate differed from today's semiarid climate with a minor rainy season during winter. Cumulatively our coral d18O, d18Oseawater and model findings indicate a mid-LIG northward expansion of the South American Intertropical Convergence Zone into the southern Caribbean Sea, highlighting the importance of regional aspects within reconstructions of LIG hydroclimate seasonality.
Age and alkenone-derived Holocene sea-surface temperature records of sediment core SO42-74KL
Sea-surface temperature reconstruction of sediments from the North Pacific and North Atlantic
Holocene climate variability is investigated in the North Pacific and North Atlantic realms, usin... more Holocene climate variability is investigated in the North Pacific and North Atlantic realms, using alkenone-derived sea-surface temperature (SST) records as well as a millennial scale simulation with a coupled atmosphere-ocean general circulation model (AOGCM). The alkenone SST data indicate a temperature increase over almost the entire North Pacific from 7 cal kyr BP to the present. A dipole pattern with a continuous cooling in the northeastern Atlantic and a warming in the eastern Mediterranean Sea and the northern Red Sea is detected in the North Atlantic realm. Similarly, SST variations are opposite in sign between the northeastern Pacific and the northeastern Atlantic. A 2300 year long AOGCM climate simulation reveals a similar SST seesaw between the northeastern Pacific and the northeastern Atlantic on centennial time scales. Our analysis of the alkenone SST data and the model results suggests fundamental inter-oceanic teleconnections during the Holocene.
Global Holocene spatial and temporal climate variability (GHOST): integrating marine Alkenone temperature estimates and three-dimensional coupled atmosphere/ocean modelling
ABSTRACT In the GHOST project, we intend to explore the climate evolution of the entire Holocene.... more ABSTRACT In the GHOST project, we intend to explore the climate evolution of the entire Holocene. Our perspective consists of two baselines: the worldwide distribution of existing, reedited, and new collected marine Alkenone temperature data; and actual but low resolution general circulation models with high computational efficiency, de- signed for long term paleoclimate studies. In order to increase spatial coverage of Holocene time series we will concentrate on marine sediments with relatively low but highest achievable resolution in the range of 50 to 200 years. Both, the data reconstruc- tion and the modelling efforts within this project, aim to investigate three-dimensional spatial-temporal patterns, i.e. two dimensions (the Earth's surface) and the time as third dimension. The advanced analysis of spatial and temporal variability in the data and in the model should enable the comprehension of climate changes detected in the data and the verification of climate variability observed in the model. Pattern analysis will provide a better understanding of the heterogenity in Holocene warming or cool- ing and the related mechanisms. The extension of the Holocene climate simulation into the next few centuries will enable a better assessment of future climatic change, due to similarities or dissimilarities between patterns of natural and anthropogenic disturbed climates.
El Nin ˜o-Southern Oscillation (ENSO) teleconnections over Europe and the Middle East are evaluat... more El Nin ˜o-Southern Oscillation (ENSO) teleconnections over Europe and the Middle East are evaluated using an oxygen isotope coral time series from the northern Red Sea and various instrumental datasets. A shift in the correlation between the Nin ˜o-3 index and the Red Sea coral record in the 1970s is detected, and it is shown that § this shift can be attributed to nonstationar y circulation regimes and related ENSO teleconnections. It is found that positive anomalies of oxygen isotope in the Red Sea coral record from the middle 1930s to the late 1960s are associated with a strong Pacific-North Atlantic teleconnection accompanied by a weak Aleutian low, a more zonal flow at midlatitudes, and La Nin ˜a conditions in tropical Pacific. In contrast, positive anomalies of oxygen isotopes in the Red Sea coral after the 1970s are related to El Nin ˜o conditions and weaker Pan-Pacific-Atlantic circulation regimes. Using the window correlation of the northern Red Sea coral record with two coral records from the tropical and subtropical Pacific, nonstationar y relationships between the tropical Pacific and the § European-Middle Eastern climate during the preinstrumental period are found. The results imply that the modulation of teleconnections at interdecadal timescales provides a limitation in the prediction and reconstruction of remote climate phenomena such as the ENSO impact over Europe.
Age and alkenone-derived Holocene sea-surface temperature records of sediment core GeoB5901-2
Age and alkenone-derived Holocene sea-surface temperature records of sediment core SO42-74KL
Ras Umm Sidd annual d18O, Sr/Ca, reconstructed Sr/Ca temperature and reconstructed d18O seawater data of coral core/colony RUS-95
Geophysical Research Letters, Jul 20, 2018
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as
Tellus A, Aug 1, 2008
Globally forced model simulations with an atmospheric general circulation model of intermediate c... more Globally forced model simulations with an atmospheric general circulation model of intermediate complexity reveal surface air temperature (SAT) and sea level pressure (SLP) variations at multidecadal time scales. In order to separate the influence of individual ocean basins on the North Atlantic multidecadal variability, we force our model with observed SST data for the period 1856-2000 for Atlantic and Pacific Oceans, separately, while outside the atmosphere is coupled with the ocean via a mixed layer slab model. The experiments indicate the Atlantic Ocean as a principal driver of North Atlantic multidecadal variability, with SAT and SLP highly in phase in the North Atlantic at about 60-70 years time scale. The Pacific impact is associated to longer period variations in the SLP field over the North Atlantic. We suggest that two distinct physical modes of multidecadal climate variability exist, one of about 70 years possibly linked with the Atlantic thermohaline circulation, the other linked with the Pacific Ocean and connected to the Atlantic Ocean via Pacific-North America teleconnections. The latter has a time scale of about 80-100 years.
Paleoceanography and paleoclimatology, Feb 1, 2018
The last interglacial (LIG; Marine Isotope Substage 5e, ~127-117 ka) experienced globally warmer ... more The last interglacial (LIG; Marine Isotope Substage 5e, ~127-117 ka) experienced globally warmer than modern temperatures; however, profound differences in regional climate occurred that are relevant to the assessment of future climate change scenarios. Tropical Atlantic sea surface temperature (SST) and hydrology are intrinsic to the spatiotemporal evolution of past and future climate. We present eight monthly resolved coral Sr/Ca and δ 18 O records (130-118 ka) to reconstruct mean western tropical Atlantic SST and seawater δ 18 O changes during the LIG. Cooler and fresher than modern surface waters are indicated for the middle of the LIG at ~126 ka. This was followed by a rapid transition to modern-like SSTs and salinities that characterized the remaining part of the LIG. Our results, which account for differences found among corals, proxies, and SST calibration uncertainties, agree with western tropical Atlantic sediment records. Together, they suggest that an oceanic regime existed that differed from today.
EGU General Assembly Conference Abstracts, Apr 1, 2018
Age and alkenone-derived Holocene sea-surface temperature records of sediment core TY93-905
Age and alkenone-derived Holocene sea-surface temperature records of sediment core SSDP-102
Age and alkenone-derived Holocene sea-surface temperature records of sediment core GeoB5901-2
Ras Umm Sidd bimonthly δ¹⁸O and Sr/Ca data of coral core/colony RUS-95
Ras Umm Sidd bimonthly δ¹⁸O and Sr/Ca data and annual d18O, Sr/Ca, reconstructed Sr/Ca temperature and reconstructed d18O seawater data of coral core/colony RUS-95
The climate of the Sahara and Arabian deserts during the Little Ice Age is not well known, due to... more The climate of the Sahara and Arabian deserts during the Little Ice Age is not well known, due to a lack of annually resolved natural and documentary archives. We present an annual reconstruction of temperature and aridity derived from Sr/Ca and oxygen isotopes in a coral of the desert-surrounded northern Red Sea. Our data indicate that the eastern Sahara and Arabian Desert did not experience pronounced cooling during the late Little Ice Age (~1750-1850), but suggest an even more arid mean climate than in the following ~150 years. The mild temperatures are broadly in line with predominantly negative phases of the North Atlantic Oscillation during the Little Ice Age. The more arid climate is best explained by meridional advection of dry continental air from Eurasia. We find evidence for an abrupt termination of the more arid climate after 1850, coincident with a reorganization of the atmospheric circulation over Europe.
(Figure 2) Monthly interpolated coral d18O and d18Oseawater record from Bonaire coral BON-24-AII.2, 125.5 ka
Pages (Bern), Oct 1, 2004
Monthly Bonaire coral δ¹⁸O and d18Oseawater from the last interglacial, 120.5 -129.7 ka ago
The seasonality of hydroclimate during past periods of warmer than modern global temperatures is ... more The seasonality of hydroclimate during past periods of warmer than modern global temperatures is a critical component for understanding future climate change scenarios. Although partially analogous to these scenarios, the last interglacial (LIG, Marine Isotope Stage 5e, ~127-117 ka) is a popular test-bed. We present coral d18O monthly resolved records from multiple Bonaire (southern Caribbean) fossil corals (Diploria strigosa) that date to between 130 and 118 ka. These records represent up to 37 years and cover a total of 105 years, offering insights into the seasonality and characteristics of LIG tropical Atlantic hydroclimate. Our coral d18O records and available coral Sr/Ca- sea surface temperature (SST) records reveal new insights into the variable relationship between the seasonality of tropical Atlantic seawater d18O (d18Oseawater) and SST. Coral d18O seasonality is found to coevolve with SST and insolation seasonality throughout the LIG, culminating in significantly higher than modern values at 124 and 126 ka. At 124 ka, we reconstruct a 2-month lead of the coral d18O vs. the Sr/Ca-SST annual cycle and increased d18Oseawater seasonality. A fully-coupled climate model simulates a concomitant increase of southern Caribbean Sea summer precipitation and depletion of summer d18Oseawater. LIG regional hydroclimate differed from today's semiarid climate with a minor rainy season during winter. Cumulatively our coral d18O, d18Oseawater and model findings indicate a mid-LIG northward expansion of the South American Intertropical Convergence Zone into the southern Caribbean Sea, highlighting the importance of regional aspects within reconstructions of LIG hydroclimate seasonality.
Age and alkenone-derived Holocene sea-surface temperature records of sediment core SO42-74KL
Sea-surface temperature reconstruction of sediments from the North Pacific and North Atlantic
Holocene climate variability is investigated in the North Pacific and North Atlantic realms, usin... more Holocene climate variability is investigated in the North Pacific and North Atlantic realms, using alkenone-derived sea-surface temperature (SST) records as well as a millennial scale simulation with a coupled atmosphere-ocean general circulation model (AOGCM). The alkenone SST data indicate a temperature increase over almost the entire North Pacific from 7 cal kyr BP to the present. A dipole pattern with a continuous cooling in the northeastern Atlantic and a warming in the eastern Mediterranean Sea and the northern Red Sea is detected in the North Atlantic realm. Similarly, SST variations are opposite in sign between the northeastern Pacific and the northeastern Atlantic. A 2300 year long AOGCM climate simulation reveals a similar SST seesaw between the northeastern Pacific and the northeastern Atlantic on centennial time scales. Our analysis of the alkenone SST data and the model results suggests fundamental inter-oceanic teleconnections during the Holocene.
Global Holocene spatial and temporal climate variability (GHOST): integrating marine Alkenone temperature estimates and three-dimensional coupled atmosphere/ocean modelling
ABSTRACT In the GHOST project, we intend to explore the climate evolution of the entire Holocene.... more ABSTRACT In the GHOST project, we intend to explore the climate evolution of the entire Holocene. Our perspective consists of two baselines: the worldwide distribution of existing, reedited, and new collected marine Alkenone temperature data; and actual but low resolution general circulation models with high computational efficiency, de- signed for long term paleoclimate studies. In order to increase spatial coverage of Holocene time series we will concentrate on marine sediments with relatively low but highest achievable resolution in the range of 50 to 200 years. Both, the data reconstruc- tion and the modelling efforts within this project, aim to investigate three-dimensional spatial-temporal patterns, i.e. two dimensions (the Earth's surface) and the time as third dimension. The advanced analysis of spatial and temporal variability in the data and in the model should enable the comprehension of climate changes detected in the data and the verification of climate variability observed in the model. Pattern analysis will provide a better understanding of the heterogenity in Holocene warming or cool- ing and the related mechanisms. The extension of the Holocene climate simulation into the next few centuries will enable a better assessment of future climatic change, due to similarities or dissimilarities between patterns of natural and anthropogenic disturbed climates.
El Nin ˜o-Southern Oscillation (ENSO) teleconnections over Europe and the Middle East are evaluat... more El Nin ˜o-Southern Oscillation (ENSO) teleconnections over Europe and the Middle East are evaluated using an oxygen isotope coral time series from the northern Red Sea and various instrumental datasets. A shift in the correlation between the Nin ˜o-3 index and the Red Sea coral record in the 1970s is detected, and it is shown that § this shift can be attributed to nonstationar y circulation regimes and related ENSO teleconnections. It is found that positive anomalies of oxygen isotope in the Red Sea coral record from the middle 1930s to the late 1960s are associated with a strong Pacific-North Atlantic teleconnection accompanied by a weak Aleutian low, a more zonal flow at midlatitudes, and La Nin ˜a conditions in tropical Pacific. In contrast, positive anomalies of oxygen isotopes in the Red Sea coral after the 1970s are related to El Nin ˜o conditions and weaker Pan-Pacific-Atlantic circulation regimes. Using the window correlation of the northern Red Sea coral record with two coral records from the tropical and subtropical Pacific, nonstationar y relationships between the tropical Pacific and the § European-Middle Eastern climate during the preinstrumental period are found. The results imply that the modulation of teleconnections at interdecadal timescales provides a limitation in the prediction and reconstruction of remote climate phenomena such as the ENSO impact over Europe.
Age and alkenone-derived Holocene sea-surface temperature records of sediment core GeoB5901-2
Age and alkenone-derived Holocene sea-surface temperature records of sediment core SO42-74KL
Ras Umm Sidd annual d18O, Sr/Ca, reconstructed Sr/Ca temperature and reconstructed d18O seawater data of coral core/colony RUS-95