Climatic Drivers of Deglacial SST Variability in the Eastern Pacific

Kumar, Dervla Meegan; Tierney, Jessica E.; Bhattacharya, Tripti; Zhu, Jiang; McCarty, Logan; Murray, James

doi:10.1029/2021pa004264

Cited by 3 publications

(2 citation statements)

References 140 publications

(359 reference statements)

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“…However, these studies also suggest that the annual SST cycle in the tropical Eastern Pacific decreased during the Younger Dryas and Heinrich Stadial 1 as a result of a further south‐ward located ITCZ contrasting our results from Tahiti in the tropical Central Pacific. The elevated annual SST cycle reconstructed from Tahiti corals from the Younger Dryas, therefore, supports results from other studies that found that the southward migration of the ITCZ in the Pacific during the Younger Dryas has been only limited (Kumar et al., 2021; Xie et al., 2008). Overall, these results suggest that during most of the last deglaciation, the reduced insolation seasonality affected the SST seasonality at Tahiti only by a small amount that is below the detection limits of coral Sr/Ca‐thermometry.…”

Section: Discussionsupporting

confidence: 88%

Last Deglacial Environmental Change in the Tropical South Pacific From Tahiti Corals

Knebel,

Felis,

Asami

et al. 2024

Paleoceanog and Paleoclimatol

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On glacial‐interglacial time scales, changes in the Earth's orbital configuration control climate seasonality and mean conditions. Tropical coral skeletons can be sampled at a sufficient resolution to reconstruct past seasonality. Here, last deglacial Porites skeletons from Integrated Ocean Drilling Program Expedition 310 to Tahiti are investigated and, supported by a modern calibration, monthly resolved time series in geochemical proxies (Sr/Ca, δ18O, δ13C) are constructed. For most of the deglaciation, Sr/Ca seasonality was similar to modern (0.139 ± 0.010 mmol mol−1; 2.8 ± 0.2°C) reflecting the small change in insolation seasonality. However, during the Younger Dryas, high values in Sr/Ca seasonality (0.171 ± 0.017 mmol mol−1; 3.4 ± 0.3°C) suggest a reduced mixed layer depth and enhanced influence of the South Pacific Subtropical Gyre due to South Pacific Convergence Zone (SPCZ) inactivity. Furthermore, high amplitudes in Younger Dryas skeletal δ18O (0.40 ± 0.22 ‰) and δ13C (0.86 ± 0.22 ‰) seasonality compared to modern (δ18O = 0.29 ± 0.08 ‰; δ13C = 0.27 ± 0.08 ‰) point to elevated winter‐summer discrepancies in rainfall and runoff. Mean coral Sr/Ca variability suggests an influence of Northern Hemisphere climate events, such as the Younger Dryas cooling (+0.134 ± 0.012 mmol mol−1;−2.6 ± 0.2°C), or the Bølling–Allerød warming (+0.032 ± 0.040 mmol mol−1; −0.6 ± 0.4°C). Deglacial mean coral Δδ18O (δ18Oseawater contribution to skeletal δ18O), corrected for the ice volume effect, was elevated pointing to more saline, thus dryer conditions, likely due to a northward migration of the SPCZ. Seasonal cycles in coral δ13C were likely caused by variations in linear extension rates that were reduced during the last deglaciation (1.00 ± 0.6 cm year−1) compared to today (1.6 ± 0.3 cm year−1).

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Section: Discussionsupporting

confidence: 88%

Last Deglacial Environmental Change in the Tropical South Pacific From Tahiti Corals

Knebel,

Felis,

Asami

et al. 2024

Paleoceanog and Paleoclimatol

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“…(2007), who use a simplified model to demonstrate that the meridional SST gradient in the ETP is paced by precession. Furthermore, these processes provide a plausible mechanism to explain the lack of local glacial cooling in the EPWP despite strong cooling off the coasts of Costa Rica and Panama (Figures 4d and 4f; Meegan Kumar et al., 2021).…”

Section: Resultsmentioning

confidence: 98%

Glacial Warming in the Eastern Pacific Warm Pool

Kumar

Tierney

Bhattacharya

et al. 2022

Geophysical Research Letters

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The tight coupling between sea surface temperature (SST) in the Eastern Pacific Warm Pool (EPWP) and convection (Wang & Enfield, 2003) strongly influences Mexican and Central American hydroclimate. Air-sea interactions in the EPWP modulate the seasonal migration of the Intertropical Convergence Zone (ITCZ) (Karnauskas & Busalacchi, 2009b;Misra & Jayasankar, 2022), the intensity of the Central American Midsummer Drought (Fiedler & Lavín, 2016), and tropical cyclone activity (Crosbie & Serra, 2014). The tropical climate and complex Central American topography interact to create a heterogeneity of ecological zones that host some of the greatest diversity of endemic species on Earth. As these habitats are highly vulnerable to the impacts of modern climate change (Karmalkar et al., 2011), understanding rainfall variability driven by EPWP dynamics has profound societal, economic, and ecological implications for the region. The local air-sea interactions that drive eastern tropical Pacific (ETP) climate variability additionally have an outsized impact on global climate due to teleconnections related to the El Niño Southern Oscillation (Karnauskas & Busalacchi, 2009a;Wang & Fiedler, 2006) and heat export via the tropical overturning circulations (Atwood et al., 2020;Raymond, 2017).The relationship between the EPWP and surrounding ETP is thus key for understanding this region's climate. The gradient between the warm EPWP SSTs and cooler eastern equatorial Pacific (EEP) SSTs (i.e., the cold tongue) creates an interhemispheric sea level pressure gradient that drives cross-equatorial southerly flow (Back & Bretherton, 2009;McGauley et al., 2004;Xie et al., 2007). North (south) of the equator, the Coriolis force redirects this flow eastward (westward), which creates a positive feedback on the SST gradient and establishes the basin's distinct climatic asymmetry (Xie, 2004). Specifically, sustained convergence north of the equator

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Evaluation of global teleconnections in CMIP6 climate projections using complex networks

Dalelane

Winderlich²

2023

Earth Syst. Dynam.

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Abstract. In climatological research, the evaluation of climate models is one of the central research subjects. As an expression of large-scale dynamical processes, global teleconnections play a major role in interannual to decadal climate variability. Their realistic representation is an indispensable requirement for the simulation of climate change, both natural and anthropogenic. Therefore, the evaluation of global teleconnections is of utmost importance when assessing the physical plausibility of climate projections. We present an application of the graph-theoretical analysis tool δ-MAPS, which constructs complex networks on the basis of spatio-temporal gridded data sets, here sea surface temperature and geopotential height at 500 hPa. Complex networks complement more traditional methods in the analysis of climate variability, like the classification of circulation regimes or empirical orthogonal functions, assuming a new non-linear perspective. While doing so, a number of technical tools and metrics, borrowed from different fields of data science, are implemented into the δ-MAPS framework in order to overcome specific challenges posed by our target problem. Those are trend empirical orthogonal functions (EOFs), distance correlation and distance multicorrelation, and the structural similarity index. δ-MAPS is a two-stage algorithm. In the first place, it assembles grid cells with highly coherent temporal evolution into so-called domains. In a second step, the teleconnections between the domains are inferred by means of the non-linear distance correlation. We construct 2 unipartite and 1 bipartite network for 22 historical CMIP6 climate projections and 2 century-long coupled reanalyses (CERA-20C and 20CRv3). Potential non-stationarity is taken into account by the use of moving time windows. The networks derived from projection data are compared to those from reanalyses. Our results indicate that no single climate projection outperforms all others in every aspect of the evaluation. But there are indeed models which tend to perform better/worse in many aspects. Differences in model performance are generally low within the geopotential height unipartite networks but higher in sea surface temperature and most pronounced in the bipartite network representing the interaction between ocean and atmosphere.

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Climatic Drivers of Deglacial SST Variability in the Eastern Pacific

Cited by 3 publications

References 140 publications

Last Deglacial Environmental Change in the Tropical South Pacific From Tahiti Corals

Last Deglacial Environmental Change in the Tropical South Pacific From Tahiti Corals

Glacial Warming in the Eastern Pacific Warm Pool

Evaluation of global teleconnections in CMIP6 climate projections using complex networks

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