Response of Thermohaline Circulation to Freshwater Forcing under Present-Day and LGM Conditions

Abstract Responses of the thermohaline circulation (THC) to freshwater forcing (hosing) in the subpolar North Atlantic Ocean under present-day and the last glacial maximum (LGM) conditions are investigated using the National Center for Atmospheric Research Community Climate System Model versions 2 and 3. Three sets of simulations are analyzed, with each set including a control run and a freshwater hosing run. The first two sets are under present-day conditions with an open and closed Bering Strait. The third one is under LGM conditions, which has a closed Bering Strait. Results show that the THC nearly collapses in all three hosing runs when the freshwater forcing is turned on. The full recovery of the THC, however, is at least a century earlier in the open Bering Strait run than the closed Bering Strait and LGM runs. This is because the excessive freshwater is diverged almost equally toward north and south from the subpolar North Atlantic when the Bering Strait is open. A significant portion of the freshwater flowing northward into the Arctic exits into the North Pacific via a reversed Bering Strait Throughflow, which accelerates the THC recovery. When the Bering Strait is closed, this Arctic to Pacific transport is absent and freshwater can only be removed through the southern end of the North Atlantic. Together with the surface freshwater excess due to precipitation, evaporation, river runoff, and melting ice in the closed Bering Strait experiments after the hosing, the removal of the excessive freshwater takes longer, and this slows the recovery of the THC. Although the background conditions are quite different between the present-day closed Bering Strait run and the LGM run, the THC responds to the freshwater forcing added in the North Atlantic in a very similar manner.

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Polycyclic Aromatic Hydrocarbons in the North Atlantic Ocean and the Arctic Ocean: Spatial Distribution and Water Mass Transport

SSRN Electronic Journal ◽

10.2139/ssrn.3940194 ◽

2021 ◽

Author(s):

Mengyang Liu ◽

Minggang Cai ◽

Mengshan Duan ◽

Meng Chen ◽

Rainer Lohmann ◽

...

Keyword(s):

Spatial Distribution ◽

North Atlantic ◽

Aromatic Hydrocarbons ◽

Water Mass ◽

North Atlantic Ocean ◽

The Arctic ◽

The North ◽

The Arctic Ocean ◽

Polycyclic Aromatic ◽

The North Atlantic

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Effect of the North Atlantic Thermohaline Circulation on Changes in Climatic Conditions and River Flow in Poland

Water ◽

10.3390/w11081622 ◽

2019 ◽

Vol 11 (8) ◽

pp. 1622 ◽

Cited By ~ 1

Author(s):

Dariusz Wrzesiński ◽

Andrzej A. Marsz ◽

Anna Styszyńska ◽

Leszek Sobkowiak

Keyword(s):

North Atlantic ◽

Cloud Cover ◽

River Flow ◽

Thermohaline Circulation ◽

Sunshine Duration ◽

The Arctic ◽

Strong Increase ◽

The North ◽

The North Atlantic ◽

Atlantic Thermohaline Circulation

The purpose of this study is to find connections between the North Atlantic Thermohaline Circulation (NA THC), climate elements, such as cloud cover, precipitation, air temperature, sunshine duration, and relative humidity, and flow of rivers in Poland. The intensity of NA THC was characterized by the DG3L index, which was established to assess changes in the amount of heat transported by NA THC along with the transport of water to the Arctic. The paper explains and discusses the mechanism of impact of the NA THC changeability on the elements of the catchment water balance variability. The positive and negative phases of the DG3L index are strongly correlated with the heat anomalies in the upper layer of the North Atlantic waters. The obtained results show that changes of NA THC have significant impact on weather conditions and selected climate elements in Poland. Statistically significant positive correlations were found between the DG3L index and average annual air temperatures, particularly in April, July, and August, while negative between the DG3L index and the total cloud cover. Consequently, in the years with the positive values of the DG3L index, there are favorable conditions for the strong increase in evaporation and evapotranspiration from the ground surface. This has impact on flow of rivers in Poland, which shows considerable regional differences.

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The behaviour of 236U in the North Atlantic Ocean assessed from numerical modelling: A new evaluation of the input function into the Arctic

The Science of The Total Environment ◽

10.1016/j.scitotenv.2018.01.058 ◽

2018 ◽

Vol 626 ◽

pp. 255-263 ◽

Cited By ~ 4

Author(s):

R. Periáñez ◽

Kyung-Suk Suh ◽

Byung-Il Min ◽

M. Villa-Alfageme

Keyword(s):

Numerical Modelling ◽

Atlantic Ocean ◽

North Atlantic ◽

North Atlantic Ocean ◽

Input Function ◽

The Arctic ◽

The North ◽

The North Atlantic

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On the peopling of the Americas: molecular evidence for the Paleoamerican and the Solutrean models

10.1101/130989 ◽

2017 ◽

Cited By ~ 3

Author(s):

Dejian Yuan ◽

Shi Huang

Keyword(s):

North Atlantic ◽

North Atlantic Ocean ◽

Molecular Evidence ◽

Bering Strait ◽

East Asians ◽

The North ◽

Pack Ice ◽

Peopling Of The Americas ◽

Close Relationship ◽

The North Atlantic

AbstractMorphological and archaeological studies suggest that the Americas were first occupied by non-Mongoloids with Australo-Melanesian traits (the Paleoamerican model), which was subsequently followed by Southwest Europeans coming in along the pack ice of the North Atlantic Ocean (the Solutrean model) and by East Asians and Siberians arriving by way of the Bering Strait. Past DNA studies, however, have produced different accounts. With a better understanding of genetic diversity, we have now reinterpreted public DNA data. Consistent with our recent finding of a close relationship between South Pacific populations and Denisovans or Neanderthals who were archaic Africans with Eurasian admixtures, the ∼9500 year old Kennewick Man skeleton with Australo-Melanesian affinity from North America was about equally related to Europeans and Africans, least related to East Asians among present-day people, and most related to the ∼42000 year old Neanderthal Mezmaiskaya-2 from Adygea Russia among ancient Eurasian DNAs. The ∼12700 year old Anzick-1 of the Clovis culture was most related to the ∼18720 year old El Miron of the Magdalenian culture in Spain among ancient DNAs. Amerindian mtDNA haplotypes, unlike their Eurasian sister haplotypes, share informative SNPs with Australo-Melanesians, Africans, or Neanderthals. These results suggest a unifying account of informative findings on the settlement of the Americas.

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Enhancement of the North Atlantic CO<sub>2</sub> sink by Arctic Waters

Biogeosciences ◽

10.5194/bg-18-1689-2021 ◽

2021 ◽

Vol 18 (5) ◽

pp. 1689-1701

Author(s):

Jon Olafsson ◽

Solveig R. Olafsdottir ◽

Taro Takahashi ◽

Magnus Danielsen ◽

Thorarinn S. Arnarson

Keyword(s):

North Atlantic ◽

Thermohaline Circulation ◽

Atlantic Water ◽

Water Masses ◽

The Arctic ◽

Arctic Water ◽

The North ◽

The North Atlantic ◽

Co2 Sink ◽

The One

Abstract. The North Atlantic north of 50∘ N is one of the most intense ocean sink areas for atmospheric CO2 considering the flux per unit area, 0.27 Pg-C yr−1, equivalent to −2.5 mol C m−2 yr−1. The northwest Atlantic Ocean is a region with high anthropogenic carbon inventories. This is on account of processes which sustain CO2 air–sea fluxes, in particular strong seasonal winds, ocean heat loss, deep convective mixing, and CO2 drawdown by primary production. The region is in the northern limb of the global thermohaline circulation, a path for the long-term deep-sea sequestration of carbon dioxide. The surface water masses in the North Atlantic are of contrasting origins and character, with the northward-flowing North Atlantic Drift, a Gulf Stream offspring, on the one hand and on the other hand the cold southward-moving low-salinity Polar and Arctic waters with signatures from Arctic freshwater sources. We have studied by observation the CO2 air–sea flux of the relevant water masses in the vicinity of Iceland in all seasons and in different years. Here we show that the highest ocean CO2 influx is to the Arctic and Polar waters, respectively, -3.8±0.4 and -4.4±0.3 mol C m−2 yr−1. These waters are CO2 undersaturated in all seasons. The Atlantic Water is a weak or neutral sink, near CO2 saturation, after poleward drift from subtropical latitudes. These characteristics of the three water masses are confirmed by data from observations covering 30 years. We relate the Polar Water and Arctic Water persistent undersaturation and CO2 influx to the excess alkalinity derived from Arctic sources. Carbonate chemistry equilibrium calculations clearly indicate that the excess alkalinity may support at least 0.058 Pg-C yr−1, a significant portion of the North Atlantic CO2 sink. The Arctic contribution to the North Atlantic CO2 sink which we reveal was previously unrecognized. However, we point out that there are gaps and conflicts in the knowledge about the Arctic alkalinity and carbonate budgets and that future trends in the North Atlantic CO2 sink are connected to developments in the rapidly warming and changing Arctic. The results we present need to be taken into consideration for the following question: will the North Atlantic continue to absorb CO2 in the future as it has in the past?

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Climate feedbacks induced by the North Atlantic freshwater forcing in a coupled model of intermediate complexity

Revista Brasileira de Meteorologia ◽

10.1590/s0102-77862010000100009 ◽

2010 ◽

Vol 25 (1) ◽

pp. 103-113 ◽

Cited By ~ 2

Author(s):

Flávio Barbosa Justino ◽

Jeferson Prietsch Machado

Keyword(s):

Heat Transport ◽

North Atlantic ◽

Thermohaline Circulation ◽

Coupled Model ◽

The North ◽

Poleward Heat Transport ◽

Freshwater Forcing ◽

Oceanic Response ◽

The North Atlantic ◽

The Tropics

Based on coupled model simulations (ECBilt-Clio), we investigate the atmospheric and oceanic response to sustained freshwater input into the North Atlantic under the glacial maximum background state. The results demonstrate that a weakening of the thermohaline circulation triggered by weaker density flux leads to rapid changes in global sea-ice volume and reduced poleward heat transport in the Northern Hemisphere (NH). In the Southern Hemisphere (SH), however, the oceanic heat transport increases substantially. This in turn leads to strong cooling over the North Atlantic whereas the SH extratropical region warms up. The suppression of the NADW also drastically changes the atmospheric circulation. The associated northward wind anomalies over the North Atlantic increase the warm air advection from the tropics and induce the transport of tropical saltier water to mid-latitudes. This negative atmospheric-oceanic feedback should play an important role to resume the NADW, after the freshwater forcing ends up.

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