Changes in the seasonal cycle of the Atlantic meridional heat transport in a RCP 8.5 climate projection in MPI-ESM

Fischer, Matthias; Domeisen, Daniela I. V.; Müller, Wolfgang A.; Baehr, Johanna

doi:10.5194/esd-8-129-2017

Cited by 4 publications

(8 citation statements)

References 88 publications

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“…Similarly, the impact of climate change on marine primary production and upper-ocean nutrient concentrations has considerable spread among global Earth system models (Bopp et al, 2013;Fu et al, 2016). Nevertheless, in the subpolar North Atlantic, the majority of models show a negative response under emission scenario RCP8.5 due to a weakening of the vertical nutrient supply from intermediate depths to the upper ocean.…”

Section: Model Evaluationmentioning

confidence: 99%

“…The nutrient concentrations of the water masses flushing the shelf are primarily controlled by the maximum depth of the wintertime mixed layer (MLD) west of the shelf break (e.g., Holliday, 2003;Williams et al, 2011;Holt et al, 2012;Gröger et al, 2013;Mathis et al, 2018). The warming and freshening of the upper North Atlantic projected by global climate models induces a weakening of the buoyancy-driven convection and thus a reduction of the wintertime MLD and upper-ocean nutrient concentration (e.g., Yool et al, 2015;Fu et al, 2016;Alexander et al, 2018). Accordingly, previous downscaling simulations mainly based on the Special Report on Emissions Scenarios (SRES) emission scenario A1B indicated that a nutrient decline in the upper NE Atlantic would lead to a similar nutrient decline on the NWES, limiting net primary production and atmospheric CO 2 uptake in open shelf areas (e.g., Holt et al, 2012;Gröger et al, 2013;Wakelin et al, 2015;Schrum et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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The impact of meltwater discharge from the Greenland ice sheet on the Atlantic nutrient supply to the northwest European shelf

Mathis¹,

Mikolajewicz²

2020

Ocean Sci.

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Abstract. Projected future shoaling of the wintertime mixed layer in the northeast (NE) Atlantic has been shown to induce a regime shift in the main nutrient supply pathway from the Atlantic to the northwest European shelf (NWES) near the end of the 21st century. While reduced winter convection leads to a substantial decrease in the vertical nutrient supply and biological productivity in the open ocean, vertical mixing processes at the shelf break maintain a connection to the subpycnocline nutrient pool and thus productivity on the shelf. Here, we investigate how meltwater discharge from the Greenland ice sheet (GIS), not yet taken into account, impacts the mixed layer shoaling and the regime shift in terms of spatial distribution and temporal variability. To this end, we have downscaled sensitivity experiments by a global Earth system model for various GIS melting rates with a regionally coupled ocean–atmosphere climate system model. The model results indicate that increasing GIS meltwater discharge leads to a general intensification of the regime shift. Atlantic subpycnocline water masses mixed up at the shelf break become richer in nutrients and thus further limit the projected nutrient decline on the shelf. Moreover, the stronger vertical nutrient gradient through the pycnocline results in an enhanced interannual variability of on-shelf nutrient fluxes which, however, do not significantly increase variations in nutrient concentrations and primary production on the shelf. Due to the impact of the GIS meltwater discharge on the NE Atlantic mixed layer depth, the regime shift becomes initiated earlier in the century. The effect on the onset timing, though, is found to be strongly damped by the weakening of the Atlantic meridional overturning circulation. A GIS melting rate that is even 10 times higher than expected for emission scenario Representative Concentration Pathway (RCP) 8.5 would not lead to an onset of the regime shift until the 2070s.

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Section: Model Evaluationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The impact of meltwater discharge from the Greenland ice sheet on the Atlantic nutrient supply to the northwest European shelf

Mathis¹,

Mikolajewicz²

2020

Ocean Sci.

View full text Add to dashboard Cite

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“…A brief discussion is provided on the link to ocean circulation, for a more detailed discussion on the ocean changes refer to Fischer et al (2017). It is likely that large-scale changes in the ocean circulation drive the SST changes (Drijfhout et al 2012).…”

Section: Simulated Local Response Of the Coupled Model In The Cmip5 Cmentioning

confidence: 99%

“…These have consequences for the SST gradients. A detailed discussion of the changes in ocean circulation is given in Fischer et al (2017). For this reason, we will give only a very brief summary on this topic in Sect.…”

mentioning

confidence: 99%

“…3.1. Following on from Fischer et al (2017), our main objective of this paper is to better understand the processes controlling the atmospheric response to the changing ocean surface conditions in this scenario. For this purpose we perform sensitivity experiments with the atmospheric component of the model to partition the atmospheric response to global warming into a part that arises from local SST changes in the North Atlantic (including, in particular, SST gradient changes in the Gulf Stream region) and a part caused by local large-scale SST changes, remote SST changes, and the direct impact of radiative forcing changes on the atmosphere.…”

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confidence: 99%

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The role of local sea surface temperature pattern changes in shaping climate change in the North Atlantic sector

et al. 2018

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Beside its global effects, climate change is manifested in many regionally pronounced features mainly resulting from changes in the oceanic and atmospheric circulation. Here we investigate the influence of the North Atlantic SST on shaping the wintertime response to global warming. Our results are based on a long-term climate projection with the Max Planck Institute Earth System Model (MPI-ESM) to investigate the influence of North Atlantic sea surface temperature pattern changes on shaping the atmospheric climate change signal. In sensitivity experiments with the model's atmospheric component we decompose the response into components controlled by the local SST structure and components controlled by global/remote changes. MPI-ESM simulates a global warming response in SST similar to other climate models: there is a warming minimum-or "warming hole"-in the subpolar North Atlantic, and the sharp SST gradients associated with the Gulf Stream and the North Atlantic Current shift northward by a few a degrees. Over the warming hole, global warming causes a relatively weak increase in rainfall. Beyond this, our experiments show more localized effects, likely resulting from future SST gradient changes in the North Atlantic. This includes a significant precipitation decrease to the south of the Gulf Stream despite increased underlying SSTs. Since this region is characterised by a strong band of precipitation in the current climate, this is contrary to the usual case that wet regions become wetter and dry regions become drier in a warmer climate. A moisture budget analysis identifies a complex interplay of various processes in the region of modified SST gradients: reduced surface winds cause a decrease in evaporation; and thermodynamic, modified atmospheric eddy transports, and coastal processes cause a change in the moisture convergence. The changes in the the North Atlantic storm track are mainly controlled by the non-regional changes in the forcing. The impact of the local SST pattern changes on regions outside the North Atlantic is small in our setup.

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Orbital and millennial northern mid-latitude westerlies over the last glacial period

Song

Yin

et al. 2019

Clim Dyn

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Changes in the seasonal cycle of the Atlantic meridional heat transport in a RCP 8.5 climate projection in MPI-ESM

Cited by 4 publications

References 88 publications

The impact of meltwater discharge from the Greenland ice sheet on the Atlantic nutrient supply to the northwest European shelf

The impact of meltwater discharge from the Greenland ice sheet on the Atlantic nutrient supply to the northwest European shelf

The role of local sea surface temperature pattern changes in shaping climate change in the North Atlantic sector

Orbital and millennial northern mid-latitude westerlies over the last glacial period

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