A dynamic giant: changes in North Pacific circulation, biogeochemistry, and CO2 over the last ice age

<p>The North Pacific has been thought of as a sleeping giant in Earth&#8217;s climate system.&#160; Despite being a major reservoir of heat, nutrients, and carbon, the lack of deep water formation in this region today limits the exchange of these properties.&#160; Here, using a variety of new and published sediment core data, alongside Earth system modeling, we provide evidence that the North Pacific giant is in fact a dynamic player in Earth&#8217;s climate system, with active PMOC during the LGM and deep water formation during HS1.&#160; We also demonstrate a persistent Atlantic-Pacific seesaw in deep water formation during rapid climate change events, and discuss the impact of these changes on regional climate and global CO<sub>2</sub>.</p>

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Deep‐Water Formation in the North Pacific During the Late Miocene Global Cooling

Paleoceanography and Paleoclimatology ◽

10.1029/2020pa003946 ◽

2021 ◽

Vol 36 (2) ◽

Author(s):

Lina Zhai ◽

Shiming Wan ◽

Christophe Colin ◽

Debo Zhao ◽

Yuntao Ye ◽

...

Keyword(s):

Deep Water ◽

Late Miocene ◽

North Pacific ◽

Deep Water Formation ◽

The North ◽

Global Cooling ◽

Water Formation ◽

The North Pacific

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The global ocean circulation on a retrograde rotating earth

Climate of the Past ◽

10.5194/cp-7-487-2011 ◽

2011 ◽

Vol 7 (2) ◽

pp. 487-499 ◽

Cited By ~ 3

Author(s):

V. Kamphuis ◽

S. E. Huisman ◽

H. A. Dijkstra

Keyword(s):

Ocean Circulation ◽

Deep Water ◽

North Pacific ◽

Global Ocean ◽

Freshwater Flux ◽

Deep Water Formation ◽

The North ◽

Water Formation ◽

Global Ocean Circulation ◽

The North Pacific

Abstract. To understand the three-dimensional ocean circulation patterns that have occurred in past continental geometries, it is crucial to study the role of the present-day continental geometry and surface (wind stress and buoyancy) forcing on the present-day global ocean circulation. This circulation, often referred to as the Conveyor state, is characterised by an Atlantic Meridional Overturning Circulation (MOC) with a deep water formation at northern latitudes and the absence of such a deep water formation in the North Pacific. This MOC asymmetry is often attributed to the difference in surface freshwater flux: the Atlantic as a whole is a basin with net evaporation, while the Pacific receives net precipitation. This issue is revisited in this paper by considering the global ocean circulation on a retrograde rotating earth, computing an equilibrium state of the coupled atmosphere-ocean-land surface-sea ice model CCSM3. The Atlantic-Pacific asymmetry in surface freshwater flux is indeed reversed, but the ocean circulation pattern is not an Inverse Conveyor state (with deep water formation in the North Pacific) as there is relatively weak but intermittently strong deep water formation in the North Atlantic. Using a fully-implicit, global ocean-only model the stability properties of the Atlantic MOC on a retrograde rotating earth are also investigated, showing a similar regime of multiple equilibria as in the present-day case. These results indicate that the present-day asymmetry in surface freshwater flux is not the most important factor setting the Atlantic-Pacific salinity difference and, thereby, the asymmetry in the global MOC.

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Deep water formation in the North Pacific and deglacial CO2rise

Paleoceanography ◽

10.1002/2013pa002570 ◽

2014 ◽

Vol 29 (6) ◽

pp. 645-667 ◽

Cited By ~ 72

Author(s):

James W. B. Rae ◽

Michael Sarnthein ◽

Gavin L. Foster ◽

Andy Ridgwell ◽

Pieter M. Grootes ◽

...

Keyword(s):

Deep Water ◽

North Pacific ◽

Deep Water Formation ◽

The North ◽

Water Formation ◽

The North Pacific

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The global ocean circulation on a retrograde rotating earth

Climate of the Past Discussions ◽

10.5194/cpd-6-2455-2010 ◽

2010 ◽

Vol 6 (6) ◽

pp. 2455-2482

Author(s):

V. Kamphuis ◽

S. E. Huisman ◽

H. A. Dijkstra

Keyword(s):

Ocean Circulation ◽

Deep Water ◽

North Pacific ◽

Global Ocean ◽

Freshwater Flux ◽

Deep Water Formation ◽

The North ◽

Water Formation ◽

Global Ocean Circulation ◽

The North Pacific

Abstract. To understand the three-dimensional ocean circulation patterns that have occurred in past continental geometries, it is crucial to study the role of the present-day continental geometry and surface (wind stress and buoyancy) forcing on the present-day global ocean circulation. This circulation, often referred to as the Conveyor state, is characterized by an Atlantic Meridional Overturning Circulation (MOC) with deep water formation at northern latitudes and the absence of such deep water formation in the North Pacific. This MOC asymmetry is often attributed to the difference in surface freshwater flux: the North Atlantic is a basin with net evaporation, while the North Pacific receives net precipitation. This issue is revisited in this paper by considering the global ocean circulation on a retrograde rotating earth, computing an equilibrium state of the coupled atmosphere-ocean-land surface-sea ice model CCSM3. The Atlantic-Pacific asymmetry in surface freshwater flux is indeed reversed but the ocean circulation pattern is not an Inverse Conveyor state (with deep water formation in the North Pacific) as there is strong and highly variable deep water formation in the North Atlantic. Using a fully-implicit, global ocean-only model also the stability properties of the Atlantic MOC on a retrograde rotating earth are investigated, showing a similar regime of multiple equilibria as in the present-day case. These results demonstrate that the present-day asymmetry in surface freshwater flux is not a crucial factor for the Atlantic-Pacific asymmetry in the global MOC.

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Deep water formation in the North Atlantic Ocean during the last ice age

Nature ◽

10.1038/286479a0 ◽

1980 ◽

Vol 286 (5772) ◽

pp. 479-482 ◽

Cited By ~ 156

Author(s):

Jean-Claude Duplessy ◽

J. Moyes ◽

C. Pujol

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

Deep Water ◽

North Atlantic Ocean ◽

Ice Age ◽

Deep Water Formation ◽

The North ◽

Water Formation ◽

Last Ice Age ◽

The North Atlantic

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Freshening of the Labrador Sea as a trigger for Little Ice Age development

Climate of the Past ◽

10.5194/cp-13-317-2017 ◽

2017 ◽

Vol 13 (4) ◽

pp. 317-331 ◽

Cited By ~ 10

Author(s):

Montserrat Alonso-Garcia ◽

Helga (Kikki) F. Kleiven ◽

Jerry F. McManus ◽

Paola Moffa-Sanchez ◽

Wallace S. Broecker ◽

...

Keyword(s):

Ocean Circulation ◽

North Atlantic ◽

Deep Water ◽

Little Ice Age ◽

Ice Age ◽

Labrador Sea ◽

Deep Water Formation ◽

The North ◽

Water Formation ◽

The North Atlantic

Abstract. Arctic freshwater discharges to the Labrador Sea from melting glaciers and sea ice can have a large impact on ocean circulation dynamics in the North Atlantic, modifying climate and deep water formation in this region. In this study, we present for the first time a high resolution record of ice rafting in the Labrador Sea over the last millennium to assess the effects of freshwater discharges in this region on ocean circulation and climate. The occurrence of ice-rafted debris (IRD) in the Labrador Sea was studied using sediments from Site GS06-144-03 (57.29° N, 48.37° W; 3432 m water depth). IRD from the fraction 63–150 µm shows particularly high concentrations during the intervals ∼  AD 1000–1100, ∼  1150–1250, ∼  1400–1450, ∼  1650–1700 and ∼  1750–1800. The first two intervals occurred during the Medieval Climate Anomaly (MCA), whereas the others took place within the Little Ice Age (LIA). Mineralogical identification indicates that the main IRD source during the MCA was SE Greenland. In contrast, the concentration and relative abundance of hematite-stained grains reflects an increase in the contribution of Arctic ice during the LIA. The comparison of our Labrador Sea IRD records with other climate proxies from the subpolar North Atlantic allowed us to propose a sequence of processes that led to the cooling that occurred during the LIA, particularly in the Northern Hemisphere. This study reveals that the warm climate of the MCA may have enhanced iceberg calving along the SE Greenland coast and, as a result, freshened the subpolar gyre (SPG). Consequently, SPG circulation switched to a weaker mode and reduced convection in the Labrador Sea, decreasing its contribution to the North Atlantic deep water formation and, thus, reducing the amount of heat transported to high latitudes. This situation of weak SPG circulation may have made the North Atlantic climate more unstable, inducing a state in which external forcings (e.g. reduced solar irradiance and volcanic eruptions) could easily drive periods of severe cold conditions in Europe and the North Atlantic like the LIA. This analysis indicates that a freshening of the SPG may play a crucial role in the development of cold events during the Holocene, which may be of key importance for predictions about future climate.

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Freshwater routing in eddy-permitting simulations of the last deglacial: the impact of realistic freshwater discharge

Climate of the Past ◽

10.5194/cp-17-2327-2021 ◽

2021 ◽

Vol 17 (6) ◽

pp. 2327-2341

Author(s):

Ryan Love ◽

Heather J. Andres ◽

Alan Condron ◽

Lev Tarasov

Keyword(s):

North Atlantic ◽

Deep Water ◽

Large Scale ◽

Bering Strait ◽

Deep Water Formation ◽

The North ◽

Water Formation ◽

Glacial Runoff ◽

The North Atlantic ◽

The Impact

Abstract. Freshwater, in the form of glacial runoff, is hypothesized to play a critical role in centennial- to millennial-scale climate variability, such as the Younger Dryas and Dansgaard–Oeschger events, but this relationship is not straightforward. Large-scale glacial runoff events, such as Meltwater Pulse 1a (MWP1a), are not always temporally proximal to subsequent large-scale cooling. Moreover, the typical design of hosing experiments that support this relationship tends to artificially amplify the climate response. This study explores the impact that limitations in the representation of runoff in conventional “hosing” simulations has on our understanding of this relationship by examining where coastally released freshwater is transported when it reaches the ocean. We particularly focus on the impact of (1) the injection of freshwater directly over sites of deep-water formation (DWF) rather than at runoff locations (i.e. hosing), (2) excessive freshwater injection volumes (often by a factor of 5), and (3) the use of present-day (rather than palaeo) ocean gateways. We track the routing of glaciologically constrained freshwater volumes from four different inferred injection locations in a suite of eddy-permitting glacial ocean simulations using the Massachusetts Institute of Technology General Circulation Model (MITgcm) under both open and closed Bering Strait conditions. Restricting freshwater forcing values to realistic ranges results in less spreading of freshwater across the North Atlantic and indicates that the freshwater anomalies over DWF sites depend strongly on the geographical location of meltwater input. In particular, freshwater released into the Gulf of Mexico generates a very weak freshwater signal over DWF regions as a result of entrainment by the turbulent Gulf Stream. In contrast, freshwater released into the Arctic with an open Bering Strait or from the Eurasian ice sheet is found to generate the largest salinity anomalies over DWF regions in the North Atlantic and GIN (Greenland–Iceland–Norwegian) seas region respectively. Experiments show that when the Bering Strait is open, the Mackenzie River source exhibits more than twice as much freshening of the North Atlantic deep-water formation regions as when the Bering Strait is closed. Our results illustrate that applying freshwater hosing directly into the North Atlantic with even “realistic” freshwater amounts still overestimates the amount of terrestrial runoff reaching DWF regions. Given the simulated salinity anomaly distributions and the lack of reconstructed impact on deep-water formation during the Bølling–Allerød, our results support that the majority of the North American contribution to MWP1a was not routed through the Mackenzie River.

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Seasonal Evolution of Aleutian Low Pressure Systems: Implications for the North Pacific Subpolar Circulation*

Journal of Physical Oceanography ◽

10.1175/2008jpo3891.1 ◽

2009 ◽

Vol 39 (6) ◽

pp. 1317-1339 ◽

Cited By ~ 44

Author(s):

Robert S. Pickart ◽

Alison M. Macdonald ◽

G. W. K. Moore ◽

Ian A. Renfrew ◽

John E. Walsh ◽

...

Keyword(s):

North Pacific ◽

Lower Troposphere ◽

Gulf Of Alaska ◽

Low Pressure ◽

Aleutian Low ◽

The North ◽

Early Fall ◽

The Impact ◽

The North Pacific ◽

Low Pressure Systems

Abstract The seasonal change in the development of Aleutian low pressure systems from early fall to early winter is analyzed using a combination of meteorological reanalysis fields, satellite sea surface temperature (SST) data, and satellite wind data. The time period of the study is September–December 2002, although results are shown to be representative of the long-term climatology. Characteristics of the storms were documented as they progressed across the North Pacific, including their path, central pressure, deepening rate, and speed of translation. Clear patterns emerged. Storms tended to deepen in two distinct geographical locations—the Gulf of Alaska in early fall and the western North Pacific in late fall. In the Gulf of Alaska, a quasi-permanent “notch” in the SST distribution is argued to be of significance. The signature of the notch is imprinted in the atmosphere, resulting in a region of enhanced cyclonic potential vorticity in the lower troposphere that is conducive for storm development. Later in the season, as winter approaches and the Sea of Okhotsk becomes partially ice covered and cold, the air emanating from the Asian continent leads to enhanced baroclinicity in the region south of Kamchatka. This corresponds to enhanced storm cyclogenesis in that region. Consequently, there is a seasonal westward migration of the dominant lobe of the Aleutian low. The impact of the wind stress curl pattern resulting from these two regions of storm development on the oceanic circulation is investigated using historical hydrography. It is argued that the seasonal bimodal input of cyclonic vorticity from the wind may be partly responsible for the two distinct North Pacific subarctic gyres.

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