scholarly journals Strong deep-water formation in Baffin Bay ensured the heavy snowfall that initiated the Last Ice Age in the Northern Hemisphere

2021 ◽  
Vol 8 ◽  
pp. 39-45
Author(s):  
Robert Glenn Johnson
Keyword(s):  
Deep Water ◽  
Heavy Precipitation ◽  
Atlantic Water ◽  
Ice Age ◽  
Deep Water Formation ◽  
Heavy Snowfall ◽  
Baffin Bay ◽  
Nares Strait ◽  
Water Formation ◽  
Last Ice Age

The extremely heavy precipitation that initiated the Last Ice Age (the Wisconsin Glaciation in Canada) was caused by a strong and persistent atmospheric low-pressure system centered over the northern Labrador Sea and southern Baffin Bay. This system, called the Labrador Low, was dependent on strong deep-water formation in the northern end of Baffin Bay. The replacement for the sinking deep water consisted of warmer and more saline Irminger Current water that mixed into the northward-flowing West Greenland Current near the center of the Labrador Low. The heavy precipitation in northeastern Canada began after the stratification in Baffin Bay was eliminated by the southward flow of denser Atlantic water through the Nares Strait. This temporary flow began when the oscillating Atlantic Meridional Oceanic Circulation (AMOC) flow reached a maximum greater than today. This sent Atlantic water westward, north of Greenland and through the Nares Strait. Although the extremely heavy snowfall began the Wisconsin Glaciation in Canada, the initiation of the Last Ice Age in Eurasia was a more complex process and was delayed by about 4,000 years by formation of the Hudson Strait ice dam.

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

Nature ◽  
1980 ◽  
Vol 286 (5772) ◽  
pp. 479-482 ◽  
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

Influence of Nordic Seas dynamics on the Atlantic Water propagation and its impacts on sea ice concentration.

2021 ◽  
Author(s):  
Sourav Chatterjee ◽  
Roshin P Raj ◽  
Laurent Bertino ◽  
Nuncio Murukesh
Keyword(s):  
Sea Ice ◽  
Deep Water ◽  
Atlantic Water ◽  
The Arctic ◽  
Deep Water Formation ◽  
Sea Ice Concentration ◽  
Nordic Seas ◽  
Ice Concentration ◽  
Water Formation

<p>Enhanced intrusion of warm and saline Atlantic Water (AW) to the Arctic Ocean (AO) in recent years has drawn wide interest of the scientific community owing to its potential role in ‘Arctic Amplification’. Not only the AW has warmed over the last few decades , but its transfer efficiency have also undergone significant modifications due to changes in atmosphere and ocean dynamics at regional to large scales. The Nordic Seas (NS), in this regard, play a vital role as the major exchange of polar and sub-polar waters takes place in this region. Further, the AW and its significant modification on its way to AO via the Nordic Seas has large scale implications on e.g., deep water formation, air-sea heat fluxes. Previous studies have suggested that a change in the sub-polar gyre dynamics in the North Atlantic controls the AW anomalies that enter the NS and eventually end up in the AO. However, the role of NS dynamics in resulting in the modifications of these AW anomalies are not well studied. Here in this study, we show that the Nordic Seas are not only a passive conduit of AW anomalies but the ocean circulations in the Nordic Seas, particularly the Greenland Sea Gyre (GSG) circulation can significantly change the AW characteristics between the entry and exit point of AW in the NS. Further, it is shown that the change in GSG circulation can modify the AW heat distribution in the Nordic Seas and can potentially influence the sea ice concentration therein. Projected enhanced atmospheric forcing in the NS in a warming Arctic scenario and the warming trend of the AW can amplify the role of NS circulation in AW propagation and its impact on sea ice, freshwater budget and deep water formation.</p>

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

2017 ◽  
Vol 13 (4) ◽  
pp. 317-331 ◽  
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.

scholarly journals Multi-model based estimation of sea ice volume variations in the Baffin Bay

2020 ◽  
Author(s):  
Chao Min ◽  
Qinghua Yang ◽  
Longjiang Mu ◽  
Frank Kauker ◽  
Robert Ricker
Keyword(s):  
Sea Ice ◽  
Deep Water ◽  
Meridional Overturning Circulation ◽  
Deep Water Formation ◽  
Sea Ice Thickness ◽  
Baffin Bay ◽  
Ice Volume ◽  
Water Formation ◽  
Ensemble Mean ◽  
Meridional Overturning

Abstract. Sea ice in Baffin Bay plays an important role in the deep water formation in the Labrador Sea and contributes to the variation of the Atlantic meridional overturning circulation (AMOC) on larger scales. To quantify the sea ice volume variations in Baffin Bay, a major driver of the deep water formation, three state-of-the-art sea ice models (CMST, NAOSIM, and PIOMAS) are investigated in the melt and freezing season from 2011 to 2016. An ensemble of three estimates of the sea ice volume fluxes in Baffin Bay is generated from the three modeled sea ice thickness and NSIDC satellite derived ice drift data. Results show that the net increase of the ensemble mean sea ice volume (SIV) in Baffin Bay occurs from October to April with the largest SIV increase in December (116 ± 16 km3 month−1) and the reduction occurs from May to September with the largest SIV decline in July (−160 ± 32 km3 month−1). The maximum SIV inflow occurs in winter in all the model data consistently. The ensemble mean SIV inflow (322 ± 4 km3) reaches its maximum in winter 2013 caused by high ice velocities while the largest SIV outflow (244 ± 61 km3) occurs in spring of 2014. The long-term annual mean ice volume inflow and outflow are 437(± 53) km3 and 339(± 68) km3, respectively. Our analysis also reveals that on average, sea ice in Baffin Bay melts from May to October with a net reduction of 335 km3 in volume while it freezes from November to April with a net increase of 251 km3.

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

2020 ◽  
Author(s):  
James Rae ◽  
William Gray ◽  
Louisa Bradtmiller ◽  
Andrea Burke ◽  
Holger Gebhardt ◽  
...  
Keyword(s):  
Deep Water ◽  
North Pacific ◽  
System Modeling ◽  
Climate System ◽  
Ice Age ◽  
Deep Water Formation ◽  
The North ◽  
Water Formation ◽  
The Impact ◽  
The North Pacific

<p>The North Pacific has been thought of as a sleeping giant in Earth’s climate system.  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.  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’s climate system, with active PMOC during the LGM and deep water formation during HS1.  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>

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

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

scholarly journals Arctic–North Atlantic Interactions and Multidecadal Variability of the Meridional Overturning Circulation

2005 ◽  
Vol 18 (19) ◽  
pp. 4013-4031 ◽  
Author(s):  
Johann H. Jungclaus ◽  
Helmuth Haak ◽  
Mojib Latif ◽  
Uwe Mikolajewicz
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
Deep Water Formation ◽  
Overturning Circulation ◽  
Multidecadal Variability ◽  
Water Formation ◽  
Meridional Overturning

Abstract Analyses of a 500-yr control integration with the non-flux-adjusted coupled atmosphere–sea ice–ocean model ECHAM5/Max-Planck-Institute Ocean Model (MPI-OM) show pronounced multidecadal fluctuations of the Atlantic overturning circulation and the associated meridional heat transport. The period of the oscillations is about 70–80 yr. The low-frequency variability of the meridional overturning circulation (MOC) contributes substantially to sea surface temperature and sea ice fluctuations in the North Atlantic. The strength of the overturning circulation is related to the convective activity in the deep-water formation regions, most notably the Labrador Sea, and the time-varying control on the freshwater export from the Arctic to the convection sites modulates the overturning circulation. The variability is sustained by an interplay between the storage and release of freshwater from the central Arctic and circulation changes in the Nordic Seas that are caused by variations in the Atlantic heat and salt transport. The relatively high resolution in the deep-water formation region and the Arctic Ocean suggests that a better representation of convective and frontal processes not only leads to an improvement in the mean state but also introduces new mechanisms determining multidecadal variability in large-scale ocean circulation.

scholarly journals North Atlantic deep water formation and AMOC in CMIP5 models

Ocean Science ◽  
2017 ◽  
Vol 13 (4) ◽  
pp. 609-622 ◽  
Author(s):  
Céline Heuzé
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Deep Water ◽  
Deep Convection ◽  
The Arctic ◽  
Subpolar Gyre ◽  
Deep Water Formation ◽  
Nordic Seas ◽  
Water Formation

Abstract. Deep water formation in climate models is indicative of their ability to simulate future ocean circulation, carbon and heat uptake, and sea level rise. Present-day temperature, salinity, sea ice concentration and ocean transport in the North Atlantic subpolar gyre and Nordic Seas from 23 CMIP5 (Climate Model Intercomparison Project, phase 5) models are compared with observations to assess the biases, causes and consequences of North Atlantic deep convection in models. The majority of models convect too deep, over too large an area, too often and too far south. Deep convection occurs at the sea ice edge and is most realistic in models with accurate sea ice extent, mostly those using the CICE model. Half of the models convect in response to local cooling or salinification of the surface waters; only a third have a dynamic relationship between freshwater coming from the Arctic and deep convection. The models with the most intense deep convection have the warmest deep waters, due to a redistribution of heat through the water column. For the majority of models, the variability of the Atlantic Meridional Overturning Circulation (AMOC) is explained by the volumes of deep water produced in the subpolar gyre and Nordic Seas up to 2 years before. In turn, models with the strongest AMOC have the largest heat export to the Arctic. Understanding the dynamical drivers of deep convection and AMOC in models is hence key to realistically forecasting Arctic oceanic warming and its consequences for the global ocean circulation, cryosphere and marine life.

Assessing the stability of the AMOC during past warm climates

2021 ◽  
Author(s):  
Megan Murphy O' Connor ◽  
Christophe Colin ◽  
Audrey Morley
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Deep Water Formation ◽  
Nordic Seas ◽  
Water Formation ◽  
Rockall Trough ◽  
Eastern North Atlantic ◽  
Warm Climates

<p>There is emergent evidence that abrupt shifts of the Atlantic Meridional Overturning Circulation (AMOC) have occurred during interglacial periods, with recent observations and model simulations showing that we may have over-estimated its stability during warm climates. In this study, we present a multi-proxy reconstruction of deep-water characteristics from the Rockall Trough in the Eastern North Atlantic to assess the variability of Nordic seas and Labrador Sea deep-water formation during past interglacial periods MIS 1, 5, 11, and 19. To test the warm climate stability hypothesis and to constrain the variability of deep-water formation for past warm climates, we performed geochemical analysis on planktic (Nd isotopes) and benthic foraminifera (δ<sup>18</sup>O and δ<sup>13</sup>C) along with sedimentological analysis. This approach allows us to reconstruct paleocurrent flow strength, as well as the origin and contribution of different water masses to one of the deep-water components of the AMOC in the Rockall Trough. We found that deep-water properties varied considerably during each of our chosen periods. For example during the Holocene εNd variability is smaller (1.8 per mil) when compared to variability during MIS 19 (3.3 per mil), an interglacial that experienced very similar orbital boundary conditions. Our results confirm that deep-water variability in the eastern North Atlantic basin was more variable in previous interglacial periods when compared to our current Holocene and provide new insight into the relative contribution of Nordic Seas Deep Water and Labrador Sea Water in the Rockall trough.</p>

Sign in / Sign up

Export Citation Format

Share Document