scholarly journals Intense ocean freshening from melting glacier around the Antarctica during early twenty-first century

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Xianliang L. Pan ◽  
Bofeng F. Li ◽  
Yutaka W. Watanabe
Keyword(s):  
Southern Ocean ◽  
Negative Impact ◽  
Global Climate ◽  
Dominant Role ◽  
Extreme Environment ◽  
Meridional Overturning Circulation ◽  
First Century ◽  
Early Twenty ◽  
Significant Negative Impact ◽  
Twenty First Century

AbstractWith the accelerating mass loss of Antarctic ice sheets, the freshening of the Southern Ocean coastal oceans (SOc, seas around Antarctica) is gradually intensifying, which will reduce the formation of bottom water and weaken the meridional overturning circulation, thus having a significant negative impact on the ocean’s role in regulating global climate. Due to the extreme environment of the Southern Ocean and the limitations of observational techniques, our understanding of the glacier-derived freshening of SOc is still vague. We developed a method that first provided us with an expansive understanding of glacier-derived freshening progress over the SOc. Applying this method to the observational data in the SOc from 1926 to 2016, revealed that the rate of glacier-derived freshwater input reached a maximum of 268 ± 134 Gt year−1 during the early twenty-first century. Our results indicate that during the same period, glacier melting accounted for 63%, 28%, and 92% of the total freshening occurred in the Atlantic, Indian, and Pacific sectors of the SOc, respectively. This suggests that the ice shelf basal melt in West Antarctica and the Antarctic Peninsula plays a dominant role in the freshening of the surrounding seas.

Continuing Visions

2018 ◽  
Author(s):  
Linda Freedman
Keyword(s):  
Social Activism ◽  
William Blake ◽  
First Century ◽  
Ridley Scott ◽  
American Novel ◽  
Early Twenty ◽  
Protest Group ◽  
Late Twentieth ◽  
Twenty First Century ◽  
Dead Man

The questions that drove Blake’s American reception, from its earliest moments in the nineteenth century through to the explosion of Blakeanism in the mid-twentieth century, did not disappear. Visions of America continued to be part of Blake’s late twentieth- and early twenty-first century American legacy. This chapter begins with the 1982 film Blade Runner, which was directed by the British Ridley Scott but had an American-authored screenplay and was based on a 1968 American novel, Do Androids Dream of Electric Sheep? It moves to Jim Jarmusch’s 1995 film, Dead Man and Paul Chan’s twenty-first century social activism as part of a protest group called The Friends of William Blake, exploring common themes of democracy, freedom, limit, nationhood, and poetic shape.

Contrasting patterns of early twenty-first-century glacier mass change in the Himalayas

Nature ◽  
2012 ◽  
Vol 488 (7412) ◽  
pp. 495-498 ◽  
Author(s):  
Andreas Kääb ◽  
Etienne Berthier ◽  
Christopher Nuth ◽  
Julie Gardelle ◽  
Yves Arnaud
Keyword(s):  
First Century ◽  
Mass Change ◽  
Early Twenty ◽  
Twenty First Century

Decomposing the time-mean Atlantic Meridional Overturning Circulation and its variability with latitude.

2021 ◽  
Author(s):  
Tomas Jonathan ◽  
Mike Bell ◽  
Helen Johnson ◽  
David Marshall
Keyword(s):  
Global Climate ◽  
Dominant Role ◽  
Meridional Overturning Circulation ◽  
Western Boundary ◽  
Relative Role ◽  
Overturning Circulation ◽  
Near Surface ◽  
Boundary Density ◽  
Meridional Overturning

<p>The Atlantic Meridional Overturning Circulations (AMOC) is crucial to our global climate, transporting heat and nutrients around the globe. Detecting  potential climate change signals first requires a careful characterisation of inherent natural AMOC variability. Using a hierarchy of global coupled model  control runs (HadGEM-GC3.1, HighResMIP) we decompose the overturning circulation as the sum of (near surface) Ekman, (depth-dependent) bottom velocity, eastern and western boundary density components, as a function of latitude. This decomposition proves a useful low-dimensional characterisation of the full 3-D overturning circulation. In particular, the decomposition provides a means to investigate and quantify the constraints which boundary information imposes on the overturning, and the relative role of eastern versus western contributions on different timescales. </p><p>The basin-wide time-mean contribution of each boundary component to the expected streamfunction is investigated as a function of depth, latitude and spatial resolution. Regression modelling supplemented by Correlation Adjusted coRrelation (CAR) score diagnostics provide a natural ranking of the contributions of the various components in explaining the variability of the total streamfunction. Results reveal the dominant role of the bottom component, western boundary and Ekman components at short time-scales, and of boundary density components at decadal and longer timescales.</p>

scholarly journals Atlantic Meridional Overturning Circulation (AMOC) in CMIP5 Models: RCP and Historical Simulations

2013 ◽  
Vol 26 (18) ◽  
pp. 7187-7197 ◽  
Author(s):  
Wei Cheng ◽  
John C. H. Chiang ◽  
Dongxiao Zhang
Keyword(s):  
North Atlantic ◽  
Coupled Model ◽  
Meridional Overturning Circulation ◽  
First Century ◽  
Model Intercomparison ◽  
The North ◽  
Intercomparison Project ◽  
Meridional Overturning ◽  
The North Atlantic ◽  
Twenty First Century

Abstract The Atlantic meridional overturning circulation (AMOC) simulated by 10 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) for the historical (1850–2005) and future climate is examined. The historical simulations of the AMOC mean state are more closely matched to observations than those of phase 3 of the Coupled Model Intercomparison Project (CMIP3). Similarly to CMIP3, all models predict a weakening of the AMOC in the twenty-first century, though the degree of weakening varies considerably among the models. Under the representative concentration pathway 4.5 (RCP4.5) scenario, the weakening by year 2100 is 5%–40% of the individual model's historical mean state; under RCP8.5, the weakening increases to 15%–60% over the same period. RCP4.5 leads to the stabilization of the AMOC in the second half of the twenty-first century and a slower (then weakening rate) but steady recovery thereafter, while RCP8.5 gives rise to a continuous weakening of the AMOC throughout the twenty-first century. In the CMIP5 historical simulations, all but one model exhibit a weak downward trend [ranging from −0.1 to −1.8 Sverdrup (Sv) century−1; 1 Sv ≡ 106 m3 s−1] over the twentieth century. Additionally, the multimodel ensemble–mean AMOC exhibits multidecadal variability with a ~60-yr periodicity and a peak-to-peak amplitude of ~1 Sv; all individual models project consistently onto this multidecadal mode. This multidecadal variability is significantly correlated with similar variations in the net surface shortwave radiative flux in the North Atlantic and with surface freshwater flux variations in the subpolar latitudes. Potential drivers for the twentieth-century multimodel AMOC variability, including external climate forcing and the North Atlantic Oscillation (NAO), and the implication of these results on the North Atlantic SST variability are discussed.

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