Decadal climate sensitivity of contouritic sedimentation in a dynamically coupled ice-ocean-sediment model of the North Atlantic

Abstract The twentieth-century Northern Hemisphere surface climate exhibits a long-term warming trend largely caused by anthropogenic forcing, with natural decadal climate variability superimposed on it. This study addresses the possible origin and strength of internal decadal climate variability in the Northern Hemisphere during the recent decades. The authors present results from a set of climate model simulations that suggest natural internal multidecadal climate variability in the North Atlantic–Arctic sector could have considerably contributed to the Northern Hemisphere surface warming since 1980. Although covering only a few percent of the earth’s surface, the Arctic may have provided the largest share in this. It is hypothesized that a stronger meridional overturning circulation in the Atlantic and the associated increase in northward heat transport enhanced the heat loss from the ocean to the atmosphere in the North Atlantic region and especially in the North Atlantic portion of the Arctic because of anomalously strong sea ice melt. The model results stress the potential importance of natural internal multidecadal variability originating in the North Atlantic–Arctic sector in generating interdecadal climate changes, not only on a regional scale, but also possibly on a hemispheric and even a global scale.

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The decadal climate prediction skill with focus on the North Atlantic region

10.5194/egusphere-egu2020-11243 ◽

2020 ◽

Author(s):

Shuting Yang ◽

Bo Christiansen

Keyword(s):

North Atlantic ◽

Large Degree ◽

Climate Prediction ◽

Prediction Skill ◽

Lead Times ◽

The North ◽

Ensemble Mean ◽

The North Atlantic ◽

Decadal Climate ◽

Decadal Climate Prediction

The skill of the decadal climate prediction is analyzed based on recent ensemble experiments from the CMIP5 and CMIP6 decadal climate prediction projects (DCPP) and the Community Earth System Model (CESM) Large Ensemble (LENS) Project. The experiments are initialized every year at November 1 for the period of 1960-2005 in the CMIP5 DCPP experiments and 1960-2016 for the CMIP6 DCPP models as well as the CESM LENS decadal prediction. The CMIP5/6 ensemble has 10 members for each model and the CESM ensemble has 40 members. For the considered models un-initialized (historical) ensembles with the same forcings exist. The advantage of initialization is analyzed by comparing these two sets of experiments. We find that the models agree that for lead-times between 4-10 years little effect of initialization is found except in the North Atlantic sub-polar gyre region (NASPG). This well-known result is found for all the models and is robust to temporal and spatial smoothing. In the sub-polar gyre region the ensemble mean of the forecast explains 30-40 % more of the observed variance than the ensemble mean of the historical non-initialized experiments even for lead-times of 10 years. However, the skill in the NASPG seems to a large degree to be related to the shift towards warmer temperatures around 1996. Weak or no skill is found when the sub-periods before and after 1996 are considered. We further analyze the characteristics of other climate indicators than surface temperature as well as the NAO to understand the cause and implication of the prediction skill.

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Mismatch between the depth habitat of planktonic foraminifera and the calibration depth of SST transfer functions may bias reconstructions

Climate of the Past ◽

10.5194/cp-9-859-2013 ◽

2013 ◽

Vol 9 (2) ◽

pp. 859-870 ◽

Cited By ~ 41

Author(s):

R. J. Telford ◽

C. Li ◽

M. Kucera

Keyword(s):

Climate Sensitivity ◽

North Atlantic ◽

Transfer Functions ◽

Thermal Structure ◽

Planktonic Foraminifera ◽

Near Surface ◽

The North ◽

Temperature Reconstructions ◽

The North Atlantic ◽

The Last Glacial

Abstract. We demonstrate that the temperature signal in the planktonic foraminifera assemblage data from the North Atlantic typically does not originate from near-surface waters and argue that this has the potential to bias sea surface temperature reconstructions using transfer functions calibrated against near-surface temperatures if the thermal structure of the upper few hundred metres of ocean changes over time. CMIP5 climate models indicate that ocean thermal structure in the North Atlantic changed between the Last Glacial Maximum (LGM) and the pre-industrial (PI), with some regions, mainly in the tropics, of the LGM ocean lacking good thermal analogues in the PI. Transfer functions calibrated against different depths reconstruct a marked subsurface cooling in parts of the tropical North Atlantic during the last glacial, in contrast to previous studies that reconstruct only a modest cooling. These possible biases in temperature reconstructions may affect estimates of climate sensitivity based on the difference between LGM and pre-industrial climate. Quantifying these biases has the potential to alter our understanding of LGM climate and improve estimates of climate sensitivity.

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Oscillatory Climate Modes in the Eastern Mediterranean and Their Synchronization with the North Atlantic Oscillation

Journal of Climate ◽

10.1175/2010jcli3181.1 ◽

2010 ◽

Vol 23 (15) ◽

pp. 4060-4079 ◽

Cited By ~ 43

Author(s):

Yizhak Feliks ◽

Michael Ghil ◽

Andrew W. Robertson

Keyword(s):

North Atlantic Oscillation ◽

North Atlantic ◽

Eastern Mediterranean ◽

Singular Spectrum Analysis ◽

Proxy Records ◽

The North ◽

Ethiopian Plateau ◽

The North Atlantic ◽

Decadal Climate ◽

The North Atlantic Oscillation

Abstract Oscillatory climatic modes over the North Atlantic, Ethiopian Plateau, and eastern Mediterranean were examined in instrumental and proxy records from these regions. Aside from the well-known North Atlantic Oscillation (NAO) index and the Nile River water-level records, the authors study for the first time an instrumental rainfall record from Jerusalem and a tree-ring record from the Golan Heights. The teleconnections between the regions were studied in terms of synchronization of chaotic oscillators. Standard methods for studying synchronization among such oscillators are modified by combining them with advanced spectral methods, including singular spectrum analysis. The resulting cross-spectral analysis quantifies the strength of the coupling together with the degree of synchronization. A prominent oscillatory mode with a 7–8-yr period is present in all the climatic indices studied here and is completely synchronized with the North Atlantic Oscillation. An energy analysis of the synchronization raises the possibility that this mode originates in the North Atlantic. Evidence is discussed for this mode being induced by the 7–8-yr oscillation in the position of the Gulf Stream front. A mechanism for the teleconnections between the North Atlantic, Ethiopian Plateau, and eastern Mediterranean is proposed, and implications for interannual-to-decadal climate prediction are discussed.

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The Sun's Role for Decadal Climate Predictability in the North Atlantic

10.5194/acp-2021-241 ◽

2021 ◽

Author(s):

Annika Drews ◽

Wenjuan Huo ◽

Katja Matthes ◽

Kunihiko Kodera ◽

Tim Kruschke

Keyword(s):

Solar Cycle ◽

North Atlantic ◽

Climate Modelling ◽

Climate Predictability ◽

The North ◽

Decadal Scale ◽

Decadal Climate Predictability ◽

The North Atlantic ◽

Decadal Climate ◽

Solar Influence

Abstract. Despite several studies on decadal-scale solar influence on climate, a systematic detection of solar-induced signals at the surface and the Sun's contribution to decadal climate predictability is still missing. Here, we disentangle the solar-cycle-induced climate response from internal variability and from other external forcings such as greenhouse gases. We utilize two 10-member ensemble simulations with a state-of-the-art chemistry climate model, to date a unique data set in chemistry climate modelling. We quantify the potential predictability related to the solar cycle and demonstrate that the detectability of the solar influence on surface climate depends on the magnitude of the solar cycle. Further, we show that a strong solar cycle forcing organizes and synchronizes the decadal-scale component of the North Atlantic Oscillation, the dominant mode of climate variability in the North Atlantic region.

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Improved decadal climate prediction in the North Atlantic using EnOI-assimilated initial condition

Science Bulletin ◽

10.1016/j.scib.2017.08.012 ◽

2017 ◽

Vol 62 (16) ◽

pp. 1142-1147 ◽

Cited By ~ 5

Author(s):

Min Wei ◽

Qingquan Li ◽

Xiaoge Xin ◽

Wei Zhou ◽

Zhenyu Han ◽

...

Keyword(s):

North Atlantic ◽

Climate Prediction ◽

Initial Condition ◽

The North ◽

The North Atlantic ◽

Decadal Climate ◽

Decadal Climate Prediction

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Multiple Equilibria as a Possible Mechanism for Decadal Variability in the North Atlantic Ocean

Journal of Climate ◽

10.1175/jcli-d-14-00813.1 ◽

2015 ◽

Vol 28 (22) ◽

pp. 8907-8922 ◽

Cited By ~ 9

Author(s):

Andreas Born ◽

Juliette Mignot ◽

Thomas F. Stocker

Keyword(s):

Climate Variability ◽

Conceptual Model ◽

North Atlantic ◽

Multiple Equilibria ◽

Decadal Variability ◽

Heat Content ◽

Decadal Climate Variability ◽

The North ◽

The North Atlantic ◽

Decadal Climate

Abstract Decadal climate variability in the North Atlantic has received increased attention in recent years, because modeling results suggest predictability of heat content and circulation indices several years ahead. However, determining the applicability of these results in the real world is challenging because of an incomplete understanding of the underlying mechanisms. Here, the authors show that recent attempts to reconstruct the decadal variations in one of the dominant circulation systems of the region, the subpolar gyre (SPG), are not always consistent. A coherent picture is partly recovered by a simple conceptual model solely forced by reanalyzed surface air temperatures. This confirms that surface heat flux indeed plays a leading role for this type of variability, as has been suggested in previous studies. The results further suggest that large variations in the SPG correspond to the crossing of a bifurcation point that is predicted from idealized experiments and an analytical solution of the model used herein. Performance of this conceptual model is tested against a statistical stochastic model. Hysteresis and the existence of two stable modes of the SPG circulation shape its response to forcing by atmospheric temperatures. The identification of the essential dynamics and the reduction to a minimal model of SPG variability provide a quantifiable basis and a framework for future studies on decadal climate variability and predictability.

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