Glacial deposits and ice-sheet dynamics in the north-central Baltic Sea during the last deglaciation

Boreas ◽  
2002 ◽  
Vol 31 (4) ◽  
pp. 362-377 ◽  
Author(s):  
Riko Noormets ◽  
Tom Flodén
Keyword(s):  
Baltic Sea ◽  
Ice Sheet ◽  
Last Deglaciation ◽  
Glacial Deposits ◽  
North Central ◽  
The North ◽  
The Last Deglaciation ◽  
Ice Sheet Dynamics

scholarly journals Towards understanding potential atmospheric contributions to abrupt climate changes: characterizing changes to the North Atlantic eddy-driven jet over the last deglaciation

2019 ◽  
Vol 15 (4) ◽  
pp. 1621-1646
Author(s):  
Heather J. Andres ◽  
Lev Tarasov
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Climate Changes ◽  
Ice Sheet ◽  
Wind Forcing ◽  
Last Deglaciation ◽  
Sea Ice Extent ◽  
The North ◽  
The Last Deglaciation ◽  
Background Climate

Abstract. Abrupt climate shifts of large amplitudes were common features of the Earth's climate as it transitioned into and out of the last full glacial state approximately 20 000 years ago, but their causes are not yet established. Midlatitude atmospheric dynamics may have played an important role in these climate variations through their effects on heat and precipitation distributions, sea ice extent, and wind-driven ocean circulation patterns. This study characterizes deglacial winter wind changes over the North Atlantic (NAtl) in a suite of transient deglacial simulations using the PlaSim Earth system model (run at T42 resolution) and the TraCE-21ka (T31) simulation. Though driven with yearly updates in surface elevation, we detect multiple instances of NAtl jet transitions in the PlaSim simulations that occur within 10 simulation years and a sensitivity of the jet to background climate conditions. Thus, we suggest that changes to the NAtl jet may play an important role in abrupt glacial climate changes. We identify two types of simulated wind changes over the last deglaciation. Firstly, the latitude of the NAtl eddy-driven jet shifts northward over the deglaciation in a sequence of distinct steps. Secondly, the variability in the NAtl jet gradually shifts from a Last Glacial Maximum (LGM) state with a strongly preferred jet latitude and a restricted latitudinal range to one with no single preferred latitude and a range that is at least 11∘ broader. These changes can significantly affect ocean circulation. Changes to the position of the NAtl jet alter the location of the wind forcing driving oceanic surface gyres and the limits of sea ice extent, whereas a shift to a more variable jet reduces the effectiveness of the wind forcing at driving surface ocean transports. The processes controlling these two types of changes differ on the upstream and downstream ends of the NAtl eddy-driven jet. On the upstream side over eastern North America, the elevated ice sheet margin acts as a barrier to the winds in both the PlaSim simulations and the TraCE-21ka experiment. This constrains both the position and the latitudinal variability in the jet at LGM, so the jet shifts in sync with ice sheet margin changes. In contrast, the downstream side over the eastern NAtl is more sensitive to the thermal state of the background climate. Our results suggest that the presence of an elevated ice sheet margin in the south-eastern sector of the North American ice complex strongly constrains the deglacial position of the jet over eastern North America and the western North Atlantic as well as its variability.

scholarly journals An updated radiocarbon-based ice margin chronology for the last deglaciation of the North American Ice Sheet Complex

2020 ◽  
Vol 234 ◽  
pp. 106223 ◽  
Author(s):  
April S. Dalton ◽  
Martin Margold ◽  
Chris R. Stokes ◽  
Lev Tarasov ◽  
Arthur S. Dyke ◽  
...  
Keyword(s):  
North American ◽  
Ice Sheet ◽  
Last Deglaciation ◽  
The North ◽  
The Last Deglaciation

The Glueckstadt Graben, a sedimentary record between the North and Baltic Sea in north Central Europe

2005 ◽  
Vol 397 (1-2) ◽  
pp. 113-126 ◽  
Author(s):  
Yuriy Maystrenko ◽  
Ulf Bayer ◽  
Magdalena Scheck-Wenderoth
Keyword(s):  
Baltic Sea ◽  
Central Europe ◽  
Sedimentary Record ◽  
North Central ◽  
The North ◽  
North Central Europe

III.—On Drift

1874 ◽  
Vol 1 (11) ◽  
pp. 496-510 ◽  
Author(s):  
J. G. Goodchild
Keyword(s):  
Ice Sheet ◽  
Irish Sea ◽  
Glacial Deposits ◽  
The North ◽  
The Irish Sea

In a letter to Nature for 14th May, 1874, Mr. Belt has expressed his belief that the presence of shells in glacial deposits, at whatever elevation they may be found, does not necessarily constitute a proof that the land has been depressed to that extent relatively to the level of the sea; but that in such cases as those of the drifts of the basin of the Irish Sea the shells occur in their present positions because they were thrust thither out of the bed of the sea by the ice-sheet which was advancing from the North.

scholarly journals Transient climate simulations of the deglaciation 21–9 thousand years before present; PMIP4 Core experiment design and boundary conditions

2015 ◽  
Vol 8 (10) ◽  
pp. 9045-9102 ◽  
Author(s):  
R. F. Ivanovic ◽  
L. J. Gregoire ◽  
M. Kageyama ◽  
D. M. Roche ◽  
P. J. Valdes ◽  
...  
Keyword(s):  
Working Group ◽  
Ad Hoc ◽  
Climate Models ◽  
Ice Sheet ◽  
Before Present ◽  
Last Deglaciation ◽  
Transient Simulations ◽  
The Last Deglaciation ◽  
Set Up ◽  
Core Simulation

Abstract. The last deglaciation, which marked the transition between the last glacial and present interglacial periods, was punctuated by a series of rapid (centennial and decadal) climate changes. Numerical climate models are useful for investigating mechanisms that underpin the events, especially now that some of the complex models can be run for multiple millennia. We have set up a Paleoclimate Modelling Intercomparison Project (PMIP) working group to coordinate efforts to run transient simulations of the last deglaciation, and to facilitate the dissemination of expertise between modellers and those engaged with reconstructing the climate of the last 21 thousand years. Here, we present the design of a coordinated Core simulation over the period 21–9 thousand years before present (ka) with time varying orbital forcing, greenhouse gases, ice sheets, and other geographical changes. A choice of two ice sheet reconstructions is given, but no ice sheet or iceberg meltwater should be prescribed in the Core simulation. Additional focussed simulations will also be coordinated on an ad-hoc basis by the working group, for example to investigate the effect of ice sheet and iceberg meltwater, and the uncertainty in other forcings. Some of these focussed simulations will focus on shorter durations around specific events to allow the more computationally expensive models to take part.

scholarly journals The Meridional Shift of the Midlatitude Westerlies over Arid Central Asia during the Past 21 000 Years Based on the TraCE-21ka Simulations

2020 ◽  
Vol 33 (17) ◽  
pp. 7455-7478
Author(s):  
Nanxuan Jiang ◽  
Qing Yan ◽  
Zhiqing Xu ◽  
Jian Shi ◽  
Ran Zhang
Keyword(s):  
Indian Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Last Deglaciation ◽  
The Past ◽  
The North ◽  
External Forcings ◽  
The Indian Ocean ◽  
The Last Deglaciation ◽  
The North Atlantic

AbstractTo advance our knowledge of the response of midlatitude westerlies to various external forcings, we investigate the meridional shift of midlatitude westerlies over arid central Asia (ACA) during the past 21 000 years, which experienced more varied forcings than the present day based on a set of transient simulations. Our results suggest that the evolution of midlatitude westerlies over ACA and driving factors vary with time and across seasons. In spring, the location of midlatitude westerlies over ACA oscillates largely during the last deglaciation, driven by meltwater fluxes and continental ice sheets, and then shows a long-term equatorward shift during the Holocene controlled by orbital insolation. In summer, orbital insolation dominates the meridional shift of midlatitude westerlies, with poleward and equatorward migration during the last deglaciation and the Holocene, respectively. From a thermodynamic perspective, variations in zonal winds are linked with the meridional temperature gradient based on the thermal wind relationship. From a dynamic perspective, variations in midlatitude westerlies are mainly induced by anomalous sea surface temperatures over the Indian Ocean through the Matsuno–Gill response and over the North Atlantic Ocean by the propagation of Rossby waves, or both, but their relative importance varies across forcings. Additionally, the modeled meridional shift of midlatitude westerlies is broadly consistent with geological evidence, although model–data discrepancies still exist. Overall, our study provides a possible scenario for a meridional shift of midlatitude westerlies over ACA in response to various external forcings during the past 21 000 years and highlights important roles of both the Indian Ocean and the North Atlantic Ocean in regulating Asian westerlies, which may shed light on the behavior of westerlies in the future.

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