Frontiers in Decadal Climate Variability Proceedings of a Workshop (2016) / Chapter Skim
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Modes and Mechanisms of Internal Variability
Modes and Mechanisms of Internal Variability
Pages 13-30
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From page 13... ...
, excess heat was sequestered in the subsurface tropical Pacific waters, which is a "symptom" of decadal variability. In the early 2000s, Pacific surface temperatures were cooler, and unusually strong winds caused the heat to travel to the subsurface (100-300 m)
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From page 14... ...
, two ocean observational products. (Botto Global mea temperature trends as a fun A; ( p om)
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From page 15... ...
pattern describes variability in SSTs averaged over the entire North Atlantic Ocean. The AMO index is usually calculated as the average of north Atlantic SST temperature anomalies after removing any linear trend (Enfield et al., 2001)
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Stronger trade winds cause a La Niña–like pattern of increased upwelling of cooler waters in the eastern tropical Pacific Ocean and intensified subtropical cell circulation in the atmosphere, which promotes enhanced mixing of warmer water into the subsurface of the ocean. Such enhanced mixing could account for about 50 percent of energy represented in the slowdown in GMST rise (England et al., 2014; Delworth et al., 2015)
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From page 17... ...
Sev a veral mechanisms for this va ariability have been e 2 In this context, a "pacem maker experime ent" refers to specifying a certa variable (in this case tropic ain cal Pacific SST decadal variab T bility) and allow wing the free-ruunning coupled model to respo ond.
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From page 18... ...
pacemaker experiments sh r how that model runs with impposed Pacific SS variability (re line) match observations (b ST ed black line)
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used LIM to separate the N N . North Pacific SST variability y 7 Linear Inv verse Modeling (LIM)
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co ooled in the cen ntral North Pac ific Ocean and warmed off the d coast of we estern North Am merica, reflected in a shift toward the domina d ation of the possitive phase of the Pacific Decadal Oscillation (PDO) (see Figgure)
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From page 21... ...
cific combinatio of on ponents that describes the Pacific SST trend during the slowd these comp d down in GMST rise during thi period. SOUR T is RCE: Yochanan Kushnir presenttation, Septemb 3, 2015.
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From page 22... ...
Caroline Ummenhofer from the Woods Hole Oceanographic Institution presented complementary evidence that Indian Ocean variability plays an important role in global ocean heat content and has several important regional climate implications. The Indian Ocean has also been shown to have the strongest correlation between SSTs and GMST since 1900 as compared to other ocean basins (Figure 10, bottom)
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From page 23... ...
Observed correlation between annual global mean SST and the an n nnual SST at ea grid, during 1901-2012. N ach g NOTE: The warm ming trend of SST over the Indian Ocean has been largely in phase with the overall trend in the GMST o Ts n e over the past century.
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From page 24... ...
. Many participants presented on the importance of Pacific va p e ariability as a driver for global trends, but there is also work to suggest that At , a tlantic variability can drive Pacific patterrns (Rupric ch-Robert, 2016)
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From page 25... ...
; Arctic sea ice extent; tropical atmospheric circulation; and changes in the Southern Ocean. He concluded that NAO variability drives AMOC variability, particularly on multidecadal scales, although what generates NAO variability on these longer timescales remains unknown.
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. Ting's work examines the interco ween the tropical Pacific an tropical At onnection betw nd tlantic on deccadal timescal which she said is crucia in realistica representi the les, e al ally ing hydrocclimate impac of the AMV on North Am cts V merica.
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From page 27... ...
l. generated in CMIP510 models -- whet m ther the relationship is domminated by ENNSO condition ns pical Pacific or subpolar No Atlantic SST anomalies Ting said that removing t in the trop o orth S s.
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From page 28... ...
Moreover, the temperature and salinity distributions are not well observed, which highlights the importance of sustaining subsurface observations in the seasonal ice zone, such as the Southern Ocean under-ice Argo program, Marshall concluded. 11 Winds from the west toward the east in the mid-latitudes (between 30 and 60 degrees)
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From page 29... ...
Inter hall -model differeences in the SSouthern Ocean's reesponse to wi may be re ind rent backgrou nd stratificatio in the elated to differ on seasonal ice zone. The poles are also not well represented in ea o arlier datasets used for s calculating GMST, sugg gesting that, particularly for the Arctic, G p r GMST trend ca alculations maay be undereestimated.
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