Effect of the potential melting of the Greenland Ice Sheet on the Meridional Overturning Circulation and global climate in the future

The Greenland Ice Sheet (GIS) and the Atlantic Meridional Overturning Circulation (AMOC) have been identified as possible tipping elements of the climate system, transitioning into a qualitatively different state with the crossing of a critical driver threshold. They interact via freshwater fluxes into the North Atlantic originating from a melting GIS on the one hand, and via a relative cooling around Greenland with a slowdown of the AMOC on the other. This positive-negative feedback loop raises the question how these effects will influence the overall stability of the coupled system. Here, we qualitatively explore the dynamics and in particular the emergence of cascading tipping behavior of the interacting GIS and AMOC by using process-based but still conceptual models of the individual tipping elements with a simple coupling under idealized forcing scenarios.We identify patterns of multiple tipping such as (i) overshoot cascades, developing with a temporary threshold overshoot, and (ii) rate-induced cascades, arising under very rapid changes of tipping element drivers. Their occurrence within distinct corridors of dangerous tipping pathways is affected by the melting patterns of the GIS and thus eventually by the imposed external forcing and its time scales.The conceptual nature of the proposed model does not allow for quantitative statements or projections on the emergence of tipping cascades in the climate system. Rather, our results stress that it is not only necessary to stay below a certain critical threshold to hinder tipping cascades but also to respect safe rates of environmental change to mitigate domino effects and in turn to maintain the resilience of the Earth system.

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Modeling the Influence of Greenland Ice Sheet Melting on the Atlantic Meridional Overturning Circulation During the Next Millennia

Collected Reprint Series - 2009, State of the Cryosphere: Glaciers and Ice Sheets ◽

10.1002/9781118782033.ch36 ◽

2014 ◽

pp. 1-5

Author(s):

E. Driesschaert ◽

T. Fichefet ◽

H. Goosse ◽

P. Huybrechts ◽

I. Janssens ◽

...

Keyword(s):

Ice Sheet ◽

Greenland Ice Sheet ◽

Atlantic Meridional Overturning Circulation ◽

Meridional Overturning Circulation ◽

Overturning Circulation ◽

Meridional Overturning

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Past, Present, and Future Changes in the Atlantic Meridional Overturning Circulation

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-11-00151.1 ◽

2012 ◽

Vol 93 (11) ◽

pp. 1663-1676 ◽

Cited By ~ 116

Author(s):

M. Srokosz ◽

M. Baringer ◽

H. Bryden ◽

S. Cunningham ◽

T. Delworth ◽

...

Keyword(s):

Climate Change ◽

Global Climate ◽

Surface Air Temperature ◽

Atlantic Meridional Overturning Circulation ◽

Meridional Overturning Circulation ◽

Human Populations ◽

Overturning Circulation ◽

Intergovernmental Panel ◽

The Future ◽

Meridional Overturning

Observations and numerical modeling experiments provide evidence for links between variability in the Atlantic meridional overturning circulation (AMOC) and global climate patterns. Reduction in the strength of the overturning circulation is thought to have played a key role in rapid climate change in the past and may have the potential to significantly influence climate change in the future, as noted in the last two Intergovernmental Panel on Climate Change (IPCC) assessment reports (Houghton et al.; Solomon et al.). Both IPCC reports also highlighted the significant uncertainties that exist regarding the future behavior of the AMOC under global warming. Model results suggest that changes in the AMOC can impact surface air temperature, precipitation patterns, and sea level, particularly in areas bordering the North Atlantic, thus affecting human populations. Here, the current understanding of past, present, and future changes in the AMOC and the effects of such changes on climate are reviewed. The focus is on observations of the AMOC, how the AMOC influences climate, and in what way the AMOC is likely to change over the next few decades and the twenty-first century. The potential for decadal prediction of the AMOC is also discussed. Finally, the outstanding challenges and possible future directions for AMOC research are outlined.

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Response of the North Atlantic Meridional Overturning Circulation to the Greenland Ice Sheet Freshwater input in the CESM 2.1 model

10.5194/egusphere-egu2020-9328 ◽

2020 ◽

Author(s):

Carolina Ernani da Silva ◽

Miren Vizcaino ◽

Caroline Katsman

Keyword(s):

North Atlantic ◽

Ice Sheet ◽

Stable State ◽

Greenland Ice Sheet ◽

Meridional Overturning Circulation ◽

Freshwater Input ◽

The North ◽

The Future ◽

Meridional Overturning ◽

The Impact

Coupled climate models predict a weakening of the Atlantic Meridional Overturning (AMOC) circulation in the future. However, it is not clear what is the cause of the AMOC weakening. Studies have suggested that the freshwater (FW) is an important factor in the AMOC reduction. There are different sources of FW that may play a role, such as, river discharge, sea ice melt, and precipitation. Currently, due to global warming, the Greenland Ice Sheet (GrIS) melt rate is rising, which increases the amount of freshwater (ice discharge) into the ocean. Thus, it is possible that this input of freshwater would affect the ocean circulation on a regional and global scale. Hence, the GrIS freshwater cannot be neglected. The goal of this study is to understand the impact of the freshwater from GrIS on the North AMOC (NAMOC) strength in the future. We used the Community Earth System Model (CESM) version 2.1, which contains a fully coupled and an active ice sheet, to simulate an idealized greenhouse gas scenario (1% CO2). The CO2 concentration is 1140 ppm at the end of the simulation. The results show that GrIS delivers, on average, about 0.062 Sv/yr of FW to the Subpolar North Atlantic Ocean. The bulk of the total freshwater input comes from the southeastern and southwestern parts of the ice sheet: &#160;the regions where some fast-flowing marine-terminating glaciers are located (e.g. Helheim and Kangerlussuaq). The NAMOC index (maximum barotropic stream function from above 28&#176;N and from 500 m to 5500 m depth) was calculated. It displays a fast weakening, approximately 16.7 Sv (0.11 Sv/yr), during the first 150 yrs. After that, the NAMOC reaches a stable state where the index is around 5.7 Sv (year 350). When the NAMOC index was compared to the FW from GrIS time series, we observed that change in AMOC occurs before the FW starts to increase (from year 200). Our results thus suggest that the FW input from GrIS does not cause significant changes in the AMOC strength. It is necessary to further investigate other possible causes for the strong NAMOC decline in this model.

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The influence of Greenland ice sheet melting on the Atlantic meridional overturning circulation during past and future warm periods: a model study

Climate Dynamics ◽

10.1007/s00382-014-2279-1 ◽

2014 ◽

Vol 44 (7-8) ◽

pp. 2137-2157 ◽

Cited By ~ 6

Author(s):

M. Blaschek ◽

P. Bakker ◽

H. Renssen

Keyword(s):

Ice Sheet ◽

Greenland Ice Sheet ◽

Atlantic Meridional Overturning Circulation ◽

Meridional Overturning Circulation ◽

Overturning Circulation ◽

Model Study ◽

Meridional Overturning

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High resolution evidence for linkages between NW European ice sheet instability and Atlantic Meridional Overturning Circulation

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2005.12.023 ◽

2006 ◽

Vol 243 (3-4) ◽

pp. 476-488 ◽

Cited By ~ 94

Author(s):

V.L. Peck ◽

I.R. Hall ◽

R. Zahn ◽

H. Elderfield ◽

F. Grousset ◽

...

Keyword(s):

High Resolution ◽

Ice Sheet ◽

Atlantic Meridional Overturning Circulation ◽

Meridional Overturning Circulation ◽

Overturning Circulation ◽

Meridional Overturning

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

10.5194/egusphere-egu21-1164 ◽

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

The Atlantic Meridional Overturning Circulations (AMOC) is crucial to our global climate, transporting heat and nutrients around the globe. Detecting&#160; potential climate change signals first requires a careful characterisation of inherent natural AMOC variability. Using a hierarchy of global coupled model&#160; 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.&#160;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.

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Hindcasting the continuum of Dansgaard–Oeschger variability: mechanisms, patterns and timing

Climate of the Past Discussions ◽

10.5194/cpd-9-4771-2013 ◽

2013 ◽

Vol 9 (4) ◽

pp. 4771-4806 ◽

Cited By ~ 1

Author(s):

L. Menviel ◽

A. Timmermann ◽

T. Friedrich ◽

M. H. England

Keyword(s):

North Atlantic ◽

Global Climate ◽

Ice Sheet ◽

Meridional Overturning Circulation ◽

External Boundary ◽

3 Dimensional ◽

Ice Volume ◽

Freshwater Fluxes ◽

Meridional Overturning ◽

The Continuum

Abstract. Millennial-scale variability associated with Dansgaard–Oeschger (DO) and Heinrich events (HE) is arguably one of the most puzzling climate phenomena ever discovered in paleoclimate archives. Here, we set out to elucidate the underlying dynamics by conducting a transient global hindcast simulation with a 3-dimensional intermediate complexity Earth system model covering the period 50 ka BP to 30 ka BP. The model is forced by time-varying external boundary conditions (greenhouse gases, orbital forcing, and ice sheet orography and albedo) and anomalous North Atlantic freshwater fluxes, which mimic the effects of changing Northern Hemisphere ice-volume on millennial timescales. Together these forcings generate a realistic global climate trajectory, as demonstrated by an extensive model/paleo data comparison. Our analysis is consistent with the idea that variations in ice sheet calving and related changes of the Atlantic Meridional Overturning Circulation were the main drivers for the continuum of DO and HE variability seen in paleorecords across the globe.

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The Atlantic Meridional Overturning Circulation (AMOC) simulated during interglacials and its impact on climate

10.5194/egusphere-egu21-3432 ◽

2021 ◽

Author(s):

Zhiyi Jiang ◽

Chris Brierley ◽

David Thornalley ◽

Sophie Sax

Keyword(s):

Spatial Structure ◽

Surface Temperature ◽

Global Climate ◽

Atlantic Meridional Overturning Circulation ◽

Meridional Overturning Circulation ◽

Last Interglacial ◽

Overturning Circulation ◽

Poleward Heat Transport ◽

Meridional Overturning ◽

Proxy Reconstructions

The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism of poleward heat transport and an important part of the global climate system. How it responded to past changes inforcing, such as experienced during Quaternary interglacials, is an intriguing and open question. Previous modelling studies suggest an enhanced AMOC in the mid-Holocene compared to the pre-industrial period. In previous simulations from the Palaeoclimate Modelling Intercomparison Project (PMIP), this arose from feedbacks between sea ice and AMOC changes, which also depended on resolution. Here I present aninitial analysis of the recently available PMIP4 simulations. This shows the overall strength of the AMOC does not markedly change between the mid-Holocene and piControl experiments (at least looking at the maximum of the mean meridional mass overturning streamfunction below 500m at 30oN and 50oN). This is not inconsistent with the proxy reconstructions using sortable silt and Pa/Th for the mid-Holocene. Here we analyse changes in the spatial structure of the meridional overturning circulation, along with their fingerprints on the surface temperature (computed through regression). We then estimate the percentage of the simulated surface temperature changes between the mid-Holocene and pre-industrial period that can be explained by AMOC. Furthermore, the analysis for the changes in the AMOC spatial structure has been extended to see if the same patterns of change hold for the last interglacial. The simulations will be compared to existing proxy reconstructions, as well as new palaeoceanographic reconstructions.

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