Arctic closure as a trigger for Atlantic overturning at the Eocene-Oligocene Transition

2020 ◽  
Author(s):  
David Hutchinson ◽  
Helen Coxall ◽  
Matt O'Regan ◽  
Johan Nilsson ◽  
Rodrigo Caballero ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
North Atlantic Ocean ◽  
Late Eocene ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
Deep Circulation ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

<p><strong>The Eocene-Oligocene Transition (EOT), approximately 34 Ma ago, marks a period of major global cooling and inception of the Antarctic ice sheet. Proxies of deep circulation suggest a contemporaneous onset or strengthening of the Atlantic meridional overturning circulation (AMOC). Proxy evidence of gradual salinification of the North Atlantic and tectonically driven isolation of the Arctic suggest that closing the Arctic-Atlantic gateway could have triggered the AMOC at the EOT. We demonstrate this trigger of the AMOC using a new paleoclimate model with late Eocene boundary conditions. The control simulation reproduces Eocene observations of low Arctic salinities. Subsequent closure of the Arctic-Atlantic gateway triggers the AMOC by blocking freshwater inflow from the Arctic. Salt advection feedbacks then lead to cessation of overturning in the North Pacific. These circulation changes imply major warming of the North Atlantic Ocean, and simultaneous cooling of the North Pacific, but no interhemispheric change in temperatures.</strong></p>

scholarly journals Heat transport pathways into the Arctic and their connections to surface air temperatures

2019 ◽  
Vol 19 (6) ◽  
pp. 3927-3937 ◽  
Author(s):  
Daniel Mewes ◽  
Christoph Jacobi
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Large Scale ◽  
The Arctic ◽  
Positive Temperature ◽  
Transport Pathways ◽  
Temperature Anomalies ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract. Arctic amplification causes the meridional temperature gradient between middle and high latitudes to decrease. Through this decrease the large-scale circulation in the midlatitudes may change and therefore the meridional transport of heat and moisture increases. This in turn may increase Arctic warming even further. To investigate patterns of Arctic temperature, horizontal transports and their changes in time, we analysed ERA-Interim daily winter data of vertically integrated horizontal moist static energy transport using self-organizing maps (SOMs). Three general transport pathways have been identified: the North Atlantic pathway with transport mainly over the northern Atlantic, the North Pacific pathway with transport from the Pacific region, and the Siberian pathway with transport towards the Arctic over the eastern Siberian region. Transports that originate from the North Pacific are connected to negative temperature anomalies over the central Arctic. These North Pacific pathways have been becoming less frequent during the last decades. Patterns with origin of transport in Siberia are found to have no trend and show cold temperature anomalies north of Svalbard. It was found that transport patterns that favour transport through the North Atlantic into the central Arctic are connected to positive temperature anomalies over large regions of the Arctic. These temperature anomalies resemble the warm Arctic–cold continents pattern. Further, it could be shown that transport through the North Atlantic has been becoming more frequent during the last decades.

Bathyal benthic polychaetes from the N.E. Atlantic Ocean, S.W. of the British Isles

1983 ◽  
Vol 63 (3) ◽  
pp. 593-608 ◽  
Author(s):  
Jørgen B. Kirkegaard
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
New Genus ◽  
New Combination ◽  
The Arctic ◽  
British Isles ◽  
The North ◽  
Two New Species ◽  
The North Atlantic ◽  
The North Pacific

From bathyal depths in the Bay of Biscay, southwest of the British Isles, 89 species of polychaetes are described, among which are two new species, one new genus, and one new Combination, i.e. Pholoe fauveli sp. nov., Paracapitella southwardi n.gen., n. sp., and Galathowenia oculata, new combination. Of the species taken, 52 % are also known from abyssal depths. The bathyal polychaete fauna of the North Atlantic seems to be common with that of the Arctic and the North Pacific.

scholarly journals Genetic diversity and biogeography in Chaetomorpha melagonium (Ulvophyceae, Cladophorales) based on internal transcribed spacer (ITS rDNA) sequences

2017 ◽  
Vol 60 (3) ◽  
Author(s):  
Christian Boedeker ◽  
Frederik Leliaert ◽  
Giuseppe C. Zuccarello
Keyword(s):  
Genetic Diversity ◽  
North Atlantic ◽  
North Pacific ◽  
Internal Transcribed Spacer ◽  
Distinct Species ◽  
The Arctic ◽  
The North ◽  
Rdna Sequences ◽  
The North Atlantic ◽  
The North Pacific

Abstractis a morphologically distinct species of green algae that occurs throughout the North Atlantic, the North Pacific and the Arctic Ocean. In this study, we analyzed the intraspecific genetic diversity among 14 samples of

scholarly journals The North Pacific Diatom Species Neodenticula seminae in the Modern and Holocene Sediments of the North Atlantic and Arctic

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 173
Author(s):  
Alexander Matul ◽  
Galina Kh. Kazarina
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Diatom Species ◽  
Pacific Water ◽  
The North ◽  
Holocene Sediments ◽  
The North Atlantic ◽  
The North Pacific

The paper presents micropaleontological information and observations of the North Pacific diatom species Neodenticula (N.) seminae (Simonsen and Kanaya) Akiba and Yanagisawa in the surface and Holocene sediments from the North Atlantic, Nordic, and Arctic Seas. The compilation of previously published data and new findings of this study on N. seminae in the surface sediments shows its broad occurrence as a usual element of the modern diatom microflora in the Nordic, Labrador, and Irminger Seas. The recent migration of N. seminae from its native area, the Subarctic Pacific, reflects the oceanographic shift in the late 1990s as greater transport of the warmer surface Pacific water to the Arctic causes Arctic sea-ice reduction. Micropaleontological studies of the Holocene sediments document the multiple events of N. seminae appearance in the Arctic during the latest Pleistocene and Holocene warming intervals. These observations can suggest the events of the increased influence of the North Pacific water on the Arctic environments in the past, not just during the recent warm climate amplification.

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 The Nature of the Arctic Oscillation and Diversity of the Extreme Surface Weather Anomalies It Generates

2017 ◽  
Vol 30 (14) ◽  
pp. 5563-5584 ◽  
Author(s):  
Panxi Dai ◽  
Benkui Tan
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Arctic Oscillation ◽  
Weather Prediction ◽  
The Arctic ◽  
The North ◽  
Surface Weather ◽  
The North Atlantic ◽  
The Arctic Oscillation ◽  
The North Pacific

Through a cluster analysis of daily NCEP–NCAR reanalysis data, this study demonstrates that the Arctic Oscillation (AO), defined as the leading empirical orthogonal function (EOF) of 250-hPa geopotential height anomalies, is not a unique pattern but a continuum that can be well approximated by five discrete, representative AO-like patterns. These AO-like patterns grow simultaneously from disturbances in the North Pacific, the North Atlantic, and the Arctic, and both the feedback from the high-frequency eddies in the North Pacific and North Atlantic and propagation of the low-frequency wave trains from the North Pacific across North America into the North Atlantic play important roles in the pattern formation. Furthermore, it is shown that the structures and frequencies of occurrence of the five AO-like patterns are significantly modulated by El Niño–Southern Oscillation (ENSO). Warm (cold) ENSO enhances the negative (positive) AO phase, compared with ENSO neutral winters. Finally, the surface weather effects of these AO-like patterns and their implications for the AO-related weather prediction and the AO-North Atlantic Oscillation (NAO) relationship are discussed.

scholarly journals Heat Transport Pathways into the Arctic and their Connections to Surface Air Temperatures

2018 ◽  
Author(s):  
Daniel Mewes ◽  
Christoph Jacobi
Keyword(s):  
Heat Transport ◽  
North Atlantic ◽  
North Pacific ◽  
The Arctic ◽  
Positive Temperature ◽  
Transport Pathways ◽  
Temperature Anomalies ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract. Arctic Amplification causes the meridional temperature gradient between middle and high latitudes to decrease. It is assumed that through this decrease the large-scale circulation changes and therefore the meridional transport of heat and moisture increases. This in turn may increase Arctic warming even further. To investigate patterns of Arctic temperature, horizontal fluxes and their changes in time, we analyzed ERA-Interim daily winter data of vertically integrated horizontal heat transport using Self-Organizing Maps (SOM). Three general transport pathways have been identified: the North Atlantic Pathway with transport mainly over the northern Atlantic, the North Pacific Pathway with transport from the Pacific region, and the Siberian Pathway with transport towards the Arctic over the eastern Siberian region. Transports that originate from the North Pacific are connected with negative temperature anomalies over the central Arctic. These North Pacific Pathways are getting less frequent during the last decades. Patterns with origin of transport in Siberia are found to have no trend and show cold temperature anomalies north of Svalbard. It was found that transport patterns that favor transport through the North Atlantic into the central Arctic are connected with positive temperature anomalies over large regions of the Arctic. These temperature anomalies resemble the warm Arctic cold continent effect. Further, it could be shown that transports through the North Atlantic are getting significantly more frequent during the last decades.

scholarly journals Walleye Pollock Gadus chalcogrammus, a Species with Continuous Range from the Norwegian Sea to Korea, Japan, and California: New Records from the Siberian Arctic

2021 ◽  
Vol 9 (10) ◽  
pp. 1141
Author(s):  
Alexei Orlov ◽  
Maxim Rybakov ◽  
Elena Vedishcheva ◽  
Alexander Volkov ◽  
Svetlana Orlova
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Barents Sea ◽  
Walleye Pollock ◽  
The Arctic ◽  
Meristic Characters ◽  
The North ◽  
Siberian Arctic ◽  
The North Atlantic ◽  
The North Pacific

The first records of walleye pollock Gadus chalcogrammus Pallas, 1814 in the seas of the Siberian Arctic (the Laptev Sea, the Kara Sea, the southeastern Barents Sea), are documented. Information about the external morphology (morphometric and meristic characters), photos of sagittal otoliths and fish, and data on the sequences of the CO1 mtDNA gene are presented. The results of a comparative analysis indicate that walleye pollock caught in the Siberian Arctic do not differ in principle from North Pacific and North Atlantic individuals. Previous conclusions about the conspecificity of the walleye and Norwegian pollock Theragra finnmarchica are confirmed. New captures of walleye pollock in the Siberian Arctic allow us to formulate a hypothesis about its continuous species’ range from the coasts of Norway in the North Atlantic to the coasts of Korea, Japan, and California in the North Pacific. The few records of walleye pollock in the North Atlantic originate from the North Pacific due to the transport of early pelagic juveniles to the Arctic by currents through the Bering Strait and further active westward migrations of individuals which have switched to the bentho-pelagic mode of life.

scholarly journals Control of Bering Strait Transport by the Meridional Overturning Circulation

2020 ◽  
Vol 50 (7) ◽  
pp. 1853-1870
Author(s):  
Paola Cessi
Keyword(s):  
Sea Level ◽  
North Atlantic ◽  
North Pacific ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
Bering Strait ◽  
The North ◽  
Level Difference ◽  
Sea Level Difference ◽  
The North Pacific

AbstractIt is well established that the mean transport through Bering Strait is balanced by a sea level difference between the North Pacific and the Arctic Ocean, but no mechanism has been proposed to explain this sea level difference. It is argued that the sea level difference across Bering Strait, which geostrophically balances the northward throughflow, is associated with the sea level difference between the North Pacific and the North Atlantic/Arctic. In turn, the latter difference is caused by deeper middepth isopycnals in the Indo-Pacific than in the Atlantic, especially in the northern high latitudes because there is deep water formation in the Atlantic, but not in the Pacific. Because the depth of the middepth isopycnals is associated with the dynamics of the upper branch of the meridional overturning circulation (MOC), a model is formulated that quantitatively relates the sea level difference between the North Pacific and the Arctic/North Atlantic with the wind stress in the Antarctic Circumpolar region, since this forcing powers the MOC, and with the outcropping isopycnals shared between the Northern Hemisphere and the Antarctic circumpolar region, since this controls the location of deep water formation. This implies that if the sinking associated with the MOC were to occur in the North Pacific, rather than the North Atlantic, then the Bering Strait flow would reverse. These predictions, formalized in a theoretical box model, are confirmed by a series of numerical experiments in a simplified geometry of the World Ocean, forced by steady surface wind stress, temperature, and freshwater flux.

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