Deepwater Formation in the North Pacific During the Last Glacial Termination

Science ◽  
2010 ◽  
Vol 329 (5988) ◽  
pp. 200-204 ◽  
Author(s):  
Y. Okazaki ◽  
A. Timmermann ◽  
L. Menviel ◽  
N. Harada ◽  
A. Abe-Ouchi ◽  
...  
Keyword(s):  
North Pacific ◽  
Last Glacial ◽  
The North ◽  
The North Pacific ◽  
The Last Glacial ◽  
Glacial Termination

scholarly journals Ocean circulation in the North Pacific during the last glacial termination

PAGES news ◽  
2012 ◽  
Vol 20 (2) ◽  
pp. 60-61
Author(s):  
Yusuke Okazaki ◽  
A Timmermann ◽  
L Menviel ◽  
MO Chikamoto ◽  
N Harada ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
North Pacific ◽  
Last Glacial ◽  
The North ◽  
The North Pacific ◽  
The Last Glacial ◽  
Glacial Termination

scholarly journals The LGM surface climate and atmospheric circulation over East Asia and the North Pacific in the PMIP2 coupled model simulations

2007 ◽  
Vol 3 (3) ◽  
pp. 439-451 ◽  
Author(s):  
W. Yanase ◽  
A. Abe-Ouchi
Keyword(s):  
East Asia ◽  
Last Glacial Maximum ◽  
North Pacific ◽  
General Circulation ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The North ◽  
The Last Glacial Maximum ◽  
The North Pacific ◽  
The Last Glacial

Abstract. The surface conditions and atmospheric circulation over East Asia and the North Pacific during the last glacial maximum have been investigated using outputs from several coupled atmosphere-ocean general circulation model in the PMIP2 database. During the boreal summer, the weakening of the high pressure system over the North Pacific and less precipitation over East Asia are found in most models. The latter can be attributed to reduced moisture transport. During the boreal winter, an intensification of the Aleutian low and southward shift of the westerly jet stream in the upper troposphere are found in most models. Some of the results in the present study seem to be consistent with the paleoclimatic reconstructions in the previous studies: pollen and lake-status records suggest dry climate over East Asia during the last glacial maximum, and part of the dust record has a signal that the East Asian winter monsoon was more strong and the westerly jet stream in the upper troposphere was further south during the last glacial maximum than at the present day. This result confirms that a coupled atmosphere-ocean general circulation model is a promising tool to understand not only the global climate but also the regional climate in the past.

scholarly journals North Pacific - North Atlantic linkages during the Last Glacial Termination

PAGES news ◽  
2012 ◽  
Vol 20 (2) ◽  
pp. 62-63
Author(s):  
Naomi Harada ◽  
A Timmermann ◽  
M Sato ◽  
O Seki ◽  
Y Nakamura ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Last Glacial ◽  
The Last Glacial ◽  
Glacial Termination

North Pacific Climate Response to Freshwater Forcing in the Subarctic North Atlantic: Oceanic and Atmospheric Pathways

2009 ◽  
Vol 22 (6) ◽  
pp. 1424-1445 ◽  
Author(s):  
Yuko M. Okumura ◽  
Clara Deser ◽  
Aixue Hu ◽  
Axel Timmermann ◽  
Shang-Ping Xie
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
The Arctic ◽  
Bering Strait ◽  
Aleutian Low ◽  
Freshwater Input ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific ◽  
The Last Glacial

Abstract Sudden changes of the Atlantic meridional overturning circulation (AMOC) are believed to have caused large, abrupt climate changes over many parts of the globe during the last glacial and deglacial period. This study investigates the mechanisms by which a large freshwater input to the subarctic North Atlantic and an attendant rapid weakening of the AMOC influence North Pacific climate by analyzing four different ocean–atmosphere coupled general circulation models (GCMs) under present-day or preindustrial boundary conditions. When the coupled GCMs are forced with a 1-Sv (Sv ≡ 106 m3 s−1) freshwater flux anomaly in the subarctic North Atlantic, the AMOC nearly shuts down and the North Atlantic cools significantly. The South Atlantic warms slightly, shifting the Atlantic intertropical convergence zone southward. In addition to this Atlantic ocean–atmosphere response, all of the models exhibit cooling of the North Pacific, especially along the oceanic frontal zone, consistent with paleoclimate reconstructions. The models also show deepening of the wintertime Aleutian low. Detailed analysis of one coupled GCM identifies both oceanic and atmospheric pathways from the Atlantic to the North Pacific. The oceanic teleconnection contributes a large part of the North Pacific cooling: the freshwater input to the North Atlantic raises sea level in the Arctic Ocean and reverses the Bering Strait throughflow, transporting colder, fresher water from the Arctic Ocean into the North Pacific. When the Bering Strait is closed, the cooling is greatly reduced, while the Aleutian low response is enhanced. Tropical SST anomalies in both the Atlantic and Pacific are found to be important for the equivalent barotropic response of the Aleutian low during boreal winter. The atmospheric bridge from the tropical North Atlantic is particularly important and quite sensitive to the mean state, which is poorly simulated in many coupled GCMs. The enhanced Aleutian low, in turn, cools the North Pacific by increasing surface heat fluxes and southward Ekman transport. The closure of the Bering Strait during the last glacial period suggests that the atmospheric bridge from the tropics and air–sea interaction in the North Pacific played a crucial role in the AMOC–North Pacific teleconnection.

scholarly journals Paleometeorology: visualizing mid-latitude dynamics at the synoptic level during the Last Glacial Maximum

2009 ◽  
Vol 5 (4) ◽  
pp. 1883-1899
Author(s):  
M. B. Unterman ◽  
T. J. Crowley ◽  
K. I. Hodges ◽  
S. J. Kim ◽  
D. J. Erickson
Keyword(s):  
High Resolution ◽  
Last Glacial Maximum ◽  
North Pacific ◽  
Glacial Maximum ◽  
Storm Activity ◽  
Last Glacial ◽  
The North ◽  
Depth Analysis ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. High resolution animations of the ice age surface have been developed as a tool for in-depth analysis of "paleometeorological" features. Synoptic-scale weather conditions of the Last Glacial Maximum (LGM) are simulated using the National Center for Atmospheric Research (NCAR) Community Climate Model version 3 (CCM3.6) on a globally resolved T170 (~75 km) grid domain. Model outputs have been saved at hourly intervals in order to better resolve diurnal features. The simulation has been run in tandem with a lower temporally resolved simulation of Kim et al. (2008) to enable a first-pass assessment of significance of features in the shorter run. Both simulations were forced with modified CLIMAP sea ice and sea surface temperatures (SSTs), reduced global CO2, ice sheet topography, lower sea level, and 21 000 BP orbital parameters. Results from the North Pacific show continued high storm activity during the LGM, whereas the North Atlantic tends to be more quiescent. Plots of storm tracks indicate that all North Pacific storms were steered northward into the Gulf of Alaska, bringing relatively warm air and precipitation into the region. This result is consistent with increased poleward heat transport into the region in the LGM climatological run as well as the absence of evidence for glaciation in middle Alaska. Storm-track trajectories should also have decreased upwelling along the northwest American coast – a response consistent with some geological data. The storms and other atmospheric features are illustrated in a high-resolution animation, which may also be useful as a teaching tool. Further investigation of these runs may provide additional insight into features such as wave-wave interactions, which have previously been unavailable to the research community for an alternate-Earth climate that has been at least as common as the present one over the last 500 000 years.

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