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

Hemispheric shift of the zonal mean ITCZ during the last deglaciation

2021 ◽  
Author(s):  
Chetankumar Jalihal ◽  
Uwe Mikolajewicz ◽  
Marie-Luise Kapsch
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Large Scale ◽  
Vertical Motion ◽  
Moist Static Energy ◽  
Last Deglaciation ◽  
Max Planck ◽  
The Last Deglaciation ◽  
Moist Static Energy Budget ◽  
Static Energy

<div> <p>The zonal-annual mean inter-hemispheric convergence zone (ITCZ) is located in the northern hemisphere in the modern climate. A transient simulation of the last deglaciation using the Max Planck Institute Earth System Model (MPI-ESM), suggests that the ITCZ was located in the southern hemisphere 14 kyrs ago. This shift is due to a substantial cooling of the northern hemisphere relative the southern hemisphere, after the release of melt water pulse 1a. The ITCZ compensates for these changes in the surface temperature by shifting south, thereby leading to a northward atmospheric heat transport away from the southern hemisphere. Along with the southward shift, the intensity of the precipitation within the ITCZ decreases. These changes in the intensity of precipitation can be explained by using a framework based on the moist static energy budget. We find that these changes are primarily related to the changes in the large-scale vertical motion of the atmosphere in the tropics. This affects the vertical transport of the moist static energy, and hence total gross moist stability (TGMS). </p> </div>

scholarly journals Hydrographic shifts south of Australia over the last deglaciation and possible interhemispheric linkages

2021 ◽  
pp. 1-12
Author(s):  
Matthias Moros ◽  
Patrick De Deckker ◽  
Kerstin Perner ◽  
Ulysses S. Ninnemann ◽  
Lukas Wacker ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Southern Hemisphere ◽  
Critical Role ◽  
Temperature Response ◽  
South Australia ◽  
Last Deglaciation ◽  
Tight Coupling ◽  
Oceanic Fronts ◽  
The Last Deglaciation ◽  
Circumpolar Current

Abstract Northern and southern hemispheric influences—particularly changes in Southern Hemisphere westerly winds (SSW) and Southern Ocean ventilation—triggered the stepwise atmospheric CO2 increase that accompanied the last deglaciation. One approach for gaining potential insights into past changes in SWW/CO2 upwelling is to reconstruct the positions of the northern oceanic fronts associated with the Antarctic Circumpolar Current. Using two deep-sea cores located ~600 km apart off the southern coast of Australia, we detail oceanic changes from ~23 to 6 ka using foraminifer faunal and biomarker alkenone records. Our results indicate a tight coupling between hydrographic and related frontal displacements offshore South Australia (and by analogy, possibly the entire Southern Ocean) and Northern Hemisphere (NH) climate that may help confirm previous hypotheses that the westerlies play a critical role in modulating CO2 uptake and release from the Southern Ocean on millennial and potentially even centennial timescales. The intensity and extent of the northward displacements of the Subtropical Front following well-known NH cold events seem to decrease with progressing NH ice sheet deglaciation and parallel a weakening NH temperature response and amplitude of Intertropical Convergence Zone shifts. In addition, an exceptional poleward shift of Southern Hemisphere fronts occurs during the NH Heinrich Stadial 1. This event was likely facilitated by the NH ice maximum and acted as a coup-de-grâce for glacial ocean stratification and its high CO2 capacitance. Thus, through its influence on the global atmosphere and on ocean mixing, “excessive” NH glaciation could have triggered its own demise by facilitating the destratification of the glacial ocean CO2 state.

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.

Intensified Southern Hemisphere Westerlies regulated atmospheric CO2 during the last deglaciation

Geology ◽  
2013 ◽  
Vol 41 (8) ◽  
pp. 831-834 ◽  
Author(s):  
C. Mayr ◽  
A. Lücke ◽  
S. Wagner ◽  
H. Wissel ◽  
C. Ohlendorf ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Atmospheric Co2 ◽  
Last Deglaciation ◽  
The Last Deglaciation ◽  
Southern Hemisphere Westerlies

scholarly journals Northern and southern hemisphere controls on seasonal sea surface temperatures in the Indian Ocean during the last deglaciation

2013 ◽  
Vol 28 (4) ◽  
pp. 619-632 ◽  
Author(s):  
Yiming V. Wang ◽  
Guillaume Leduc ◽  
Marcus Regenberg ◽  
Nils Andersen ◽  
Thomas Larsen ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Last Deglaciation ◽  
Surface Temperatures ◽  
The Indian Ocean ◽  
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.

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.

scholarly journals Hydrologic Change in New Zealand During the Last Deglaciation Linked to Reorganization of the Southern Hemisphere Westerly Winds

2019 ◽  
Vol 34 (12) ◽  
pp. 2158-2170 ◽  
Author(s):  
Jessica L. Hinojosa ◽  
Christopher M. Moy ◽  
Marcus Vandergoes ◽  
Sarah J. Feakins ◽  
Alex L. Sessions
Keyword(s):  
New Zealand ◽  
Southern Hemisphere ◽  
Last Deglaciation ◽  
Westerly Winds ◽  
Hydrologic Change ◽  
The Last Deglaciation ◽  
Southern Hemisphere Westerly Winds

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>

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