scholarly journals Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

2015 ◽  
Vol 11 (5) ◽  
pp. 751-764 ◽  
Author(s):  
I. Bouimetarhan ◽  
L. Dupont ◽  
H. Kuhlmann ◽  
J. Pätzold ◽  
M. Prange ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Salt Marshes ◽  
Atmospheric Precipitation ◽  
Eastern Africa ◽  
Last Deglaciation ◽  
Sea Level Changes ◽  
Climatic Fluctuations ◽  
Coastal Dynamics ◽  
Moisture Availability ◽  
The Last Deglaciation

Abstract. In tropical eastern Africa, vegetation distribution is largely controlled by regional hydrology, which has varied over the past 20 000 years. Therefore, accurate reconstructions of past vegetation and hydrological changes are crucial for a better understanding of climate variability in the tropical southeastern African region. We present high-resolution pollen records from a marine sediment core recovered offshore of the Rufiji River delta. Our data document significant shifts in pollen assemblages during the last deglaciation, identifying, through changes in both upland and lowland vegetation, specific responses of plant communities to atmospheric (precipitation) and coastal (coastal dynamics and sea-level changes) alterations. Specifically, arid conditions reflected by a maximum pollen representation of dry and open vegetation occurred during the Northern Hemisphere cold Heinrich event 1 (H1), suggesting that the expansion of drier upland vegetation was synchronous with cold Northern Hemisphere conditions. This arid period is followed by an interval in which forest and humid woodlands expanded, indicating a hydrologic shift towards more humid conditions. Droughts during H1 and the shift to humid conditions around 14.8 kyr BP in the uplands are consistent with latitudinal shifts of the intertropical convergence zone (ITCZ) driven by high-latitude Northern Hemisphere climatic fluctuations. Additionally, our results show that the lowland vegetation, consisting of well-developed salt marshes and mangroves in a successional pattern typical for vegetation occurring in intertidal habitats, has responded mainly to local coastal dynamics related to marine inundation frequencies and soil salinity in the Rufiji Delta as well as to the local moisture availability. Lowland vegetation shows a substantial expansion of mangrove trees after ~ 14.8 kyr BP, suggesting an increased moisture availability and river runoff in the coastal area. The results of this study highlight the decoupled climatic and environmental processes to which the vegetation in the uplands and the Rufiji Delta has responded during the last deglaciation.

scholarly journals Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

2014 ◽  
Vol 10 (5) ◽  
pp. 3931-3964
Author(s):  
I. Bouimetarhan ◽  
L. Dupont ◽  
H. Kuhlmann ◽  
J. Pätzold ◽  
M. Prange ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Salt Marshes ◽  
Atmospheric Precipitation ◽  
Eastern Africa ◽  
Last Deglaciation ◽  
Climatic Fluctuations ◽  
Coastal Dynamics ◽  
Moisture Availability ◽  
Dry Spell ◽  
The Last Deglaciation

Abstract. In tropical Eastern Africa, vegetation distribution is largely controlled by regional hydrology which has varied over the past 20 000 years. Therefore, accurate reconstructions of past vegetation and hydrological changes are crucial to better understand climate variability in the tropical Eastern African region. Through high-resolution pollen records from a marine sediment core recovered offshore the Rufiji River, our data show significant shifts in pollen assemblages during the last deglaciation identifying, through respective changes in both upland and lowland vegetation, specific responses of plant communities to atmospheric (precipitation) and coastal (coastal dynamics/sea level changes) alterations. Specifically, an interval of maximum pollen representation of dry and open vegetation occurred during the Northern Hemisphere cold Heinrich event 1 (H1) suggesting the expansion of drier upland vegetation under arid conditions. This dry spell is followed by an interval in which forest and humid woodland expanded, indicating a hydrologic shift towards more humid conditions. Droughts during H1 and the return to humid conditions around ~14.8 kyr BP in the uplands are primarily attributed to latitudinal shifts of the Intertropical Convergence Zone (ITCZ) driven by high-latitude Northern Hemisphere climatic fluctuations. Additionally, our results show that the lowland vegetation, consisting of a well developed salt marshes and mangroves in a successional pattern typical for vegetation occurring in intertidal habitats, has responded mainly to local coastal dynamics related to marine inundation frequencies and soil salinity in the Rufiji Delta as well as the local moisture availability. Lowland vegetation shows a substantial expansion of mangrove trees after ~14.8 kyr BP suggesting also an increased moisture availability and river runoff in the coastal area. The results of this study highlight the de-coupled climatic and environmental processes to which the vegetation in the uplands and the Rufiji Delta has responded during the last deglaciation.

Impact of relative sea-level changes since the last deglaciation on the formation of a composite paraglacial barrier

2018 ◽  
Vol 400 ◽  
pp. 76-93 ◽  
Author(s):  
Julie Billy ◽  
Nicolas Robin ◽  
Christopher J. Hein ◽  
Duncan M. FitzGerald ◽  
Raphaël Certain
Keyword(s):  
Sea Level ◽  
Last Deglaciation ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
The Last Deglaciation

scholarly journals Ice core evidence for decoupling between mid-latitude atmospheric water cycle and Greenland temperature during the last deglaciation

2018 ◽  
Author(s):  
Amaëlle Landais ◽  
Emilie Capron ◽  
Valérie Masson-Delmotte ◽  
Samuel Toucanne ◽  
Rachael Rhodes ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Environmental Changes ◽  
Ice Core ◽  
Ice Cores ◽  
Last Deglaciation ◽  
Sequence Of Events ◽  
Decadal Scale ◽  
Abrupt Changes ◽  
The Last Deglaciation

Abstract. The last deglaciation represents the most recent example of natural global warming associated with large-scale climate changes. In addition to the long-term global temperature increase, the last deglaciation onset is punctuated by a sequence of abrupt changes in the Northern Hemisphere. Such interplay between orbital- and millennial-scale variability is widely documented in paleoclimatic records but the underlying mechanisms are not fully understood. Limitations arise from the difficulty in constraining the sequence of events between external forcing, high- and low- latitude climate and environmental changes. Greenland ice cores provide sub-decadal-scale records across the last deglaciation and contain fingerprints of climate variations occurring in different regions of the Northern Hemisphere. Here, we combine new ice d-excess and 17O-excess records, tracing changes in the mid-latitudes, with ice δ18O records of polar climate. Within Heinrich Stadial 1, we demonstrate a decoupling between climatic conditions in Greenland and those of the lower latitudes. While Greenland temperature remains mostly stable from 17.5 to 14.7 ka, significant change in the mid latitudes of northern Atlantic takes place at ~ 16.2 ka, associated with warmer and wetter conditions of Greenland moisture sources. We show that this climate modification is coincident with abrupt changes in atmospheric CO2 and CH4 concentrations recorded in an Antarctic ice core. Our coherent ice core chronological framework and comparison with other paleoclimate records suggests a mechanism involving two-step freshwater fluxes in the North Atlantic associated with a southward shift of the intertropical convergence zone.

Northern Hemisphere forcing of Southern Hemisphere climate during the last deglaciation

Nature ◽  
2013 ◽  
Vol 494 (7435) ◽  
pp. 81-85 ◽  
Author(s):  
Feng He ◽  
Jeremy D. Shakun ◽  
Peter U. Clark ◽  
Anders E. Carlson ◽  
Zhengyu Liu ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Last Deglaciation ◽  
The Last Deglaciation

scholarly journals Antarctic ice dynamics amplified by Northern Hemisphere sea level forcing

2021 ◽  
Author(s):  
Natalya Gomez ◽  
Michael Weber ◽  
Peter Clark ◽  
Jerry Mitrovica ◽  
Holly Han
Keyword(s):  
Mass Loss ◽  
Sea Level ◽  
Northern Hemisphere ◽  
Ice Sheet ◽  
Last Deglaciation ◽  
Grounding Line ◽  
The Last Deglaciation ◽  
Global Sea Level ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>A longstanding hypothesis for near-synchronous evolution of global ice sheets over ice-age cycles invokes an interhemispheric sea-level forcing whereby sea-level rise due to ice loss in the Northern Hemisphere in response to insolation and greenhouse gas forcing causes grounding-line retreat of marine-based sectors of the Antarctic Ice Sheet (AIS). Recent studies have shown that the AIS experienced substantial millennial-scale variability during and after the last deglaciation, with several times of recorded increased iceberg flux and grounding line retreat coinciding, within uncertainty, with well documented global sea-level rise events, providing further evidence of this sea-level forcing. However, the sea level changes associated with ice sheet mass loss are strongly nonuniform due to gravitational, deformational and Earth rotational effects, suggesting that the response of the AIS to Northern Hemisphere sea-level forcing is more complicated than previously modelled.</p><p>We adopt an ice-sheet model coupled to a global sea-level model to show that a large or rapid Northern Hemisphere sea-level forcing enhances grounding-line advance and associated mass gain of the AIS during glaciation, and grounding-line retreat and AIS mass loss during deglaciation. Relative to models without these interactions, including the Northern Hemisphere sea-level forcing leads to a larger AIS volume during the Last Glacial Maximum (about 26,000 to 20,000 years ago), subsequent earlier grounding-line retreat and millennial-scale AIS variability throughout the last deglaciation. These findings are consistent with geologic reconstructions of the extent of the AIS during the Last Glacial Maximum and subsequent ice-sheet retreat, and with relative sea-level change in Antarctica. </p>

A Speleothem Record of Younger Dryas Cooling, Klamath Mountains, Oregon, USA

2005 ◽  
Vol 64 (2) ◽  
pp. 249-256 ◽  
Author(s):  
David A. Vacco ◽  
Peter U. Clark ◽  
Alan C. Mix ◽  
Hai Cheng ◽  
R. Lawrence Edwards
Keyword(s):  
Climate Change ◽  
Northern Hemisphere ◽  
Younger Dryas ◽  
Sampling Interval ◽  
Temperature Variability ◽  
Early Holocene ◽  
Last Deglaciation ◽  
Klamath Mountains ◽  
Scale Temperature ◽  
The Last Deglaciation

AbstractA well-dated δ18O record in a stalagmite from a cave in the Klamath Mountains, Oregon, with a sampling interval of 50 yr, indicates that the climate of this region cooled essentially synchronously with Younger Dryas climate change elsewhere in the Northern Hemisphere. The δ18O record also indicates significant century-scale temperature variability during the early Holocene. The δ13C record suggests increasing biomass over the cave through the last deglaciation, with century-scale variability but with little detectable response of vegetation to Younger Dryas cooling.

Dynamics of meltwater discharge from Northern Hemisphere ice sheets during the last deglaciation

Nature ◽  
1984 ◽  
Vol 310 (5979) ◽  
pp. 674-677 ◽  
Author(s):  
Richard H. Fillon ◽  
Douglas F. Williams
Keyword(s):  
Northern Hemisphere ◽  
Ice Sheets ◽  
Last Deglaciation ◽  
The Last Deglaciation

scholarly journals Ice core evidence for decoupling between midlatitude atmospheric water cycle and Greenland temperature during the last deglaciation

2018 ◽  
Vol 14 (10) ◽  
pp. 1405-1415 ◽  
Author(s):  
Amaëlle Landais ◽  
Emilie Capron ◽  
Valérie Masson-Delmotte ◽  
Samuel Toucanne ◽  
Rachael Rhodes ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Environmental Changes ◽  
Ice Core ◽  
Ice Cores ◽  
Last Deglaciation ◽  
Sequence Of Events ◽  
Decadal Scale ◽  
Abrupt Changes ◽  
The Last Deglaciation

Abstract. The last deglaciation represents the most recent example of natural global warming associated with large-scale climate changes. In addition to the long-term global temperature increase, the last deglaciation onset is punctuated by a sequence of abrupt changes in the Northern Hemisphere. Such interplay between orbital- and millennial-scale variability is widely documented in paleoclimatic records but the underlying mechanisms are not fully understood. Limitations arise from the difficulty in constraining the sequence of events between external forcing, high- and low- latitude climate, and environmental changes. Greenland ice cores provide sub-decadal-scale records across the last deglaciation and contain fingerprints of climate variations occurring in different regions of the Northern Hemisphere. Here, we combine new ice d-excess and 17O-excess records, tracing changes in the midlatitudes, with ice δ18O records of polar climate. Within Heinrich Stadial 1, we demonstrate a decoupling between climatic conditions in Greenland and those of the lower latitudes. While Greenland temperature remains mostly stable from 17.5 to 14.7 ka, significant change in the midlatitudes of the northern Atlantic takes place at ∼16.2 ka, associated with warmer and wetter conditions of Greenland moisture sources. We show that this climate modification is coincident with abrupt changes in atmospheric CO2 and CH4 concentrations recorded in an Antarctic ice core. Our coherent ice core chronological framework and comparison with other paleoclimate records suggests a mechanism involving two-step freshwater fluxes in the North Atlantic associated with a southward shift of the Intertropical Convergence Zone.

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