scholarly journals On the Interpretation of the North Atlantic Averaged Sea Surface Temperature

2020 ◽  
Vol 33 (14) ◽  
pp. 6025-6045
Author(s):  
Jing Sun ◽  
Mojib Latif ◽  
Wonsun Park ◽  
Taewook Park
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North Atlantic ◽  
Climate Models ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
The North ◽  
Sst Variability ◽  
The North Atlantic ◽  
Different Time Scales

AbstractThe North Atlantic (NA) basin-averaged sea surface temperature (NASST) is often used as an index to study climate variability in the NA sector. However, there is still some debate on what drives it. Based on observations and climate models, an analysis of the different influences on the NASST index and its low-pass filtered version, the Atlantic multidecadal oscillation (AMO) index, is provided. In particular, the relationships of the two indices with some of its mechanistic drivers including the Atlantic meridional overturning circulation (AMOC) are investigated. In observations, the NASST index accounts for significant SST variability over the tropical and subpolar NA. The NASST index is shown to lump together SST variability originating from different mechanisms operating on different time scales. The AMO index emphasizes the subpolar SST variability. In the climate models, the SST-anomaly pattern associated with the NASST index is similar. The AMO index, however, only represents pronounced SST variability over the extratropical NA, and this variability is significantly linked to the AMOC. There is a sensitivity of this linkage to the cold NA SST bias observed in many climate models. Models suffering from a large cold bias exhibit a relatively weak linkage between the AMOC and AMO and vice versa. Finally, the basin-averaged SST in its unfiltered form, which has been used to question a strong influence of ocean dynamics on NA SST variability, mixes together multiple types of variability occurring on different time scales and therefore underemphasizes the role of ocean dynamics in the multidecadal variability of NA SSTs.

Global Monsoon Responses to Decadal Sea Surface Temperature Variations during the Twentieth Century: Evidence from AGCM Simulations

2019 ◽  
Vol 32 (22) ◽  
pp. 7675-7695 ◽  
Author(s):  
Jie Jiang ◽  
Tianjun Zhou
Keyword(s):  
Twentieth Century ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Sea Surface ◽  
Monsoon Precipitation ◽  
The North ◽  
The North Atlantic ◽  
Sst Anomalies

Abstract Multidecadal variations in the global land monsoon were observed during the twentieth century, with an overall increasing trend from 1901 to 1955 that was followed by a decreasing trend up to 1990, but the mechanisms governing the above changes remain inconclusive. Based on the outputs of two atmospheric general circulation models (AGCMs) forced by historical sea surface temperature (SST) covering the twentieth century, supplemented with AGCM simulations forced by idealized SST anomalies representing different conditions of the North Atlantic and tropical Pacific, evidence shows that the observed changes can be partly reproduced, particularly over the Northern Hemisphere summer monsoon (NHSM) domain, demonstrating the modulation of decadal SST changes on the long-term variations in monsoon precipitation. Moisture budget analysis is performed to understand the interdecadal changes in monsoon precipitation, and the dynamic term associated with atmospheric circulation changes is found to be prominent, while the contribution of the thermodynamic term associated with humidity changes can lead to coincident wetting over the NHSM domain. The increase (decrease) in NHSM land precipitation during 1901–55 (1956–90) is associated with the strengthening (weakening) of NHSM circulation and Walker circulation. The multidecadal scale changes in atmospheric circulation are driven by SST anomalies over the North Atlantic and the Pacific. A warmer North Atlantic together with a colder eastern tropical Pacific and a warmer western subtropical Pacific can lead to a strengthened meridional gradient in mid-to-upper-tropospheric thickness and strengthened trade winds, which transport more water vapor into monsoon regions, leading to an increase in monsoon precipitation.

scholarly journals Comparison of in situ time-series of temperature with gridded sea surface temperature datasets in the North Atlantic

2009 ◽  
Vol 66 (7) ◽  
pp. 1467-1479 ◽  
Author(s):  
Sarah L. Hughes ◽  
N. Penny Holliday ◽  
Eugene Colbourne ◽  
Vladimir Ozhigin ◽  
Hedinn Valdimarsson ◽  
...  
Keyword(s):  
Time Series ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North Atlantic ◽  
Sea Surface ◽  
The North ◽  
Spatial Coverage ◽  
The North Atlantic

Abstract Hughes, S. L., Holliday, N. P., Colbourne, E., Ozhigin, V., Valdimarsson, H., Østerhus, S., and Wiltshire, K. 2009. Comparison of in situ time-series of temperature with gridded sea surface temperature datasets in the North Atlantic. – ICES Journal of Marine Science, 66: 1467–1479. Analysis of the effects of climate variability and climate change on the marine ecosystem is difficult in regions where long-term observations of ocean temperature are sparse or unavailable. Gridded sea surface temperature (SST) products, based on a combination of satellite and in situ observations, can be used to examine variability and long-term trends because they provide better spatial coverage than the limited sets of long in situ time-series. SST data from three gridded products (Reynolds/NCEP OISST.v2., Reynolds ERSST.v3, and the Hadley Centre HadISST1) are compared with long time-series of in situ measurements from ICES standard sections in the North Atlantic and Nordic Seas. The variability and trends derived from the two data sources are examined, and the usefulness of the products as a proxy for subsurface conditions is discussed.

scholarly journals North Atlantic Storm-Track Sensitivity to Projected Sea Surface Temperature: Local versus Remote Influences

2016 ◽  
Vol 29 (19) ◽  
pp. 6973-6991 ◽  
Author(s):  
Laura M. Ciasto ◽  
Camille Li ◽  
Justin J. Wettstein ◽  
Nils Gunnar Kvamstø
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North Atlantic ◽  
Storm Track ◽  
Sea Surface ◽  
System Model ◽  
Earth System ◽  
Model Version ◽  
The North ◽  
The North Atlantic

Abstract This study investigates the sensitivity of the North Atlantic storm track to future changes in local and global sea surface temperature (SST) and highlights the role of SST changes remote to the North Atlantic. Results are based on three related coupled climate models: the Community Climate System Model, version 4 (CCSM4), the Community Earth System Model, version 1 (Community Atmosphere Model, version 5) [CESM1(CAM5)], and the Norwegian Earth System Model, version 1 (intermediate resolution) (NorESM1-M). Analysis reveals noticeable intermodel differences in projected storm-track changes from the coupled simulations [i.e., the difference in 200-hPa eddy activity between the representative concentration pathway 8.5 (RCP8.5) and historical scenarios]. In the CCSM4 coupled simulations, the North Atlantic storm track undergoes a poleward shift and eastward extension. In CESM1(CAM5), the storm-track change is dominated by an intensification and eastward extension. In NorESM1-M, the storm-track change is characterized by a weaker intensification and slight eastward extension. Atmospheric experiments driven only by projected local (North Atlantic) SST changes from the coupled models fail to reproduce the magnitude and structure of the projected changes in eddy activity aloft and zonal wind from the coupled simulations. Atmospheric experiments driven by global SST and sea ice changes do, however, reproduce the eastward extension. Additional experiments suggest that increasing greenhouse gas (GHG) concentrations do not directly influence storm-track changes in the coupled simulations, although they do through GHG-induced changes in SST. The eastward extension of the North Atlantic storm track is hypothesized to be linked to western Pacific SST changes that influence tropically forced Rossby wave trains, but further studies are needed to isolate this mechanism from other dynamical adjustments to global warming.

Analysing and projecting spatial drought conditions of the Seine catchment based on ocean-atmosphere oscillations over interannual and decadal scales

2020 ◽  
Author(s):  
Kwok Pan Chun ◽  
Qing He ◽  
Bastien Dieppois ◽  
Nicolas Massei ◽  
Matthieu Fournier
Keyword(s):  
Atlantic Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Sea Surface ◽  
Positive Phase ◽  
The North ◽  
Drought Conditions ◽  
The North Atlantic

<p>Midlatitude droughts are affected by the tropical disturbances, which are linked to sea-surface temperature patterns in the Pacific and Atlantic Oceans. The combined effects of these two ocean basins manifest themselves in the variation of streamflows, from land surface filtering. In this study, we have developed a framework to explore the effects of global sea surface temperature variations along with atmospheric teleconnection patterns, on local hydroclimatic conditions related to droughts over the Seine catchment, a main waterway in northern France. Using the Standardized Runoff-discharge Index (SRI) to quantify hydrological drought conditions over the Seine, the North Atlantic Oscillation (NAO) index was found to be a significant driver for the upstream dryness between 2001 and 2015. The El Nino Southern Oscillation (ENSO) index was also found to be a significant forcing variable, but for the Seine downstream. The Atlantic Multidecadal Oscillation (AMO) and the West Mediterranean Sea (WMED) indices were significant over almost the whole Seine River basin. Results show that the drought spatial patterns of the Seine River vary differently with the atmospheric and oceanic oscillations from interannual to decadal scales. Over a small catchment with a drainage area around 78,700 square kilometres, the spatial drought variations in the Seine catchment appear to be usual, and they are likely to be related to regional conditions which drive local land surface mechanisms linked with microclimates or geological processes. In general, during the negative phase of AMO and the positive phase of ENSO, the sea surface temperature of the North Atlantic Ocean is low. The positive phase of NAO also lowers sea surface temperatures of the North Atlantic Ocean and the West Mediterranean Sea. Droughts are likely to occur at the Seine during the negative phase of AMO and the positive phase of NAO, because the cold North Atlantic Ocean has less evaporation and provides less moisture to France. Based on these results, a statistical downscaling model is developed to relate SRI to atmospheric and oceanic oscillation indices, which are derived from the Institut Pierre Simon Laplace climate model (IPSL-CM5) outputs. Using this statistical downscaling model and scenarios of Representative Concentration Pathways (RCP4.5 and RCP8.5), the drought conditions of the Seine are projected for the mid- and long-term future (2050s and 2080s). Diverse drought results are obtained. Based on relative importance of oscillation indices, the implications of diverse projections for general drought managements in midlatitude regions related to tropical sea surface temperature disturbances and atmospheric teleconnections are discussed.</p>

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