Last Glacial Maximum Sea Surface Temperatures: A Model-Data Comparison

Wang, Tao; Liu, Yi; Wei, Huang

doi:10.1080/16742834.2013.11447087

Cited by 12 publications

(4 citation statements)

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“…Hargreaves et al [2011] found that simulated NSSTs in PMIP1 and PMIP2 did not give unreliable estimates of global MARGO data when the model results were treated as an ensemble; i.e., the spread in model results was comparable to observational uncertainty. However, Dail and Wunsch [2014] found that individual PMIP2 simulations did not fit MARGO data within their uncertainties in the North Atlantic, and ensemble averages reported by Braconnot et al [2007] and individual model results from Tao et al [2013] showed North Atlantic cooling patterns with an east-west gradient opposite that seen in the data. Ballarotta et al [2013] compared LGM simulations at 1°and 0.25°hor-izontal resolution in the NEMO (Nucleus for European Modeling of the Ocean) OGCM and found that increasing resolution to permit the presence of eddies did not have a significant LGM temperature reconstructions and the World Ocean Atlas [Conkright et al, 1998].…”

Section: Computation Of Regional Averages and Uncertaintiesmentioning

confidence: 99%

“…Understanding the spatiotemporal covariance of deglacial ML δ 18 O c will also improve abilities of δ 18 O c records to constrain deglacial circulation. , Braconnot et al, 2007, Tao et al, 2013, Dail and Wunsch, 2014. The inability of models to reproduce apparently robust large-scale temperature changes at the LGM represents a gap in our understanding of how the climate was different during that time; it is unknown whether missing physics or other model errors are driving the misfit, or whether it arises from biases in the observations.…”

Section: Introductionmentioning

confidence: 99%

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Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models

Amrhein¹

2016

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Since the Last Glacial Maximum (LGM, ∼ 20, 000 years ago) air temperatures warmed, sea level rose roughly 130 meters, and atmospheric concentrations of carbon dioxide increased. This thesis combines global models and paleoceanographic observations to constrain the ocean's role in storing and transporting heat, salt, and other tracers during this time, with implications for understanding how the modern ocean works and how it might change in the future.• By combining a kinematic ocean model with "upstream" and "downstream" deglacial oxygen isotope time series from benthic and planktonic foraminifera, I show that the data are in agreement with the modern circulation, quantify their power to infer circulation changes, and propose new data locations.• An ocean general circulation model (the MITgcm) constrained to fit LGM sea surface temperature proxy observations reveals colder ocean temperatures, greater sea ice extent, and changes in ocean mixed layer depth, and suggests that some features in the data are not robust.

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Section: Computation Of Regional Averages and Uncertaintiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models

Amrhein¹

2016

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“…In the tropical oceans, Otto-Bliesner et al (2009) found that PMIP2 models had a similar range of global-mean NSST decrease to that estimated by MARGO and larger cooling in the Atlantic than in the Pacific, also in agreement with the observations, but that zonal gradients of LGM cooling in tropical Pacific near-surface waters were less pronounced than in MARGO. Model ensemble averages reported by Braconnot et al (2007) and individual model results from Tao et al (2013) show North Atlantic cooling patterns with a zonal gradient opposite that seen in the data. Data errors contributing to these disagreements could arise from chronological errors, seasonal biases, and biological effects, to name a few.…”

Section: Introductionmentioning

confidence: 93%

“…Disagreements among general circulation model (GCM) representations of the Last Glacial Maximum [LGM; circa 23-19 thousand years ago (ka); Mix et al (2001)] and between models and LGM paleoceanographic data (Braconnot et al 2007;Otto-Bliesner et al 2009;Tao et al 2013;Dail and Wunsch 2014, hereafter DW14) illustrate a gap in our knowledge of Earth's climate during that time period. Here we present a global ocean state estimate at the LGM, a dynamically consistent fit of an ocean general circulation model (OGCM) to surface ocean temperature proxies achieved Denotes content that is immediately available upon publication as open access.…”

Section: Introductionmentioning

confidence: 99%

A Global Glacial Ocean State Estimate Constrained by Upper-Ocean Temperature Proxies

et al. 2018

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We use the method of least squares with Lagrange multipliers to fit an ocean general circulation model to the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) estimate of near sea surface temperature (NSST) at the Last Glacial Maximum (LGM; circa 23-19 thousand years ago). Compared to a modern simulation, the resulting global, last-glacial ocean state estimate, which fits the MARGO data within uncertainties in a free-running coupled ocean-sea ice simulation, has global-mean NSSTs that are 28C lower and greater sea ice extent in all seasons in both the Northern and Southern Hemispheres. Increased brine rejection by sea ice formation in the Southern Ocean contributes to a stronger abyssal stratification set principally by salinity, qualitatively consistent with pore fluid measurements. The upper cell of the glacial Atlantic overturning circulation is deeper and stronger. Dye release experiments show similar distributions of Southern Ocean source waters in the glacial and modern western Atlantic, suggesting that LGM NSST data do not require a major reorganization of abyssal water masses. Outstanding challenges in reconstructing LGM ocean conditions include reducing effects from model biases and finding computationally efficient ways to incorporate abyssal tracers in global circulation inversions. Progress will be aided by the development of coupled oceanatmosphere-ice inverse models, by improving high-latitude model processes that connect the upper and abyssal oceans, and by the collection of additional paleoclimate observations.

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A review of past changes in extratropical cyclones in the northern hemisphere and what can be learned for the future

Raible

Pinto

Ludwig

et al. 2020

WIREs Climate Change

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Extratropical cyclones, a major phenomenon of the mid‐latitude atmospheric dynamics, show strong variability over a range of time scales. Future projections hint at an increase of cyclonic intensity and the associated precipitation, an important fact to be considered when developing future risk assessments. This review presents a first overview of studies which (a) puts the current variability and projected future climate changes of extratropical cyclone characteristics in a long‐term perspective, (b) shows connections to natural external forcings, and (c) deepens our understanding of cyclone intensification processes for past climate periods. We summarize the current state of knowledge for two periods in the past—the last millennium and the Last Glacial Maximum (LGM, 21,000 years ago). For these two periods, the sparse information from paleo proxy archives are compared to climate modeling results on global and regional scales. For example, strong changes of the climate mean state, induced by orbital forcing and associated feedbacks, show strong effects on different cyclone characteristics, for example, a southward shift of the storm tracks over the North Atlantic during the LGM. Other findings indicate that dynamic processes could play at least an equally important role as thermodynamic processes for the variations of cyclone‐induced precipitation. This is in contrast to the projected future changes in cyclone‐related precipitation, which are driven primarily by thermodynamic processes. The review demonstrates how a paleoclimatic view can foster an extended process understanding and be instrumental to better understand future changes in extratropical cyclones and associated characteristics. This article is categorized under: Paleoclimates and Current Trends > Modern Climate Change

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Last Glacial Maximum Sea Surface Temperatures: A Model-Data Comparison

Cited by 12 publications

References 12 publications

Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models

Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models

A Global Glacial Ocean State Estimate Constrained by Upper-Ocean Temperature Proxies

A review of past changes in extratropical cyclones in the northern hemisphere and what can be learned for the future

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