scholarly journals Estimation of Subsurface Temperature Anomaly in the North Atlantic Using a Self-Organizing Map Neural Network

2012 ◽  
Vol 29 (11) ◽  
pp. 1675-1688 ◽  
Author(s):  
Xiangbai Wu ◽  
Xiao-Hai Yan ◽  
Young-Heon Jo ◽  
W. Timothy Liu
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
Temperature Anomaly ◽  
Sea Surface ◽  
Self Organizing Map ◽  
Subsurface Temperature ◽  
The North ◽  
Subsurface Temperature Anomaly ◽  
Som Algorithm ◽  
The North Atlantic

Abstract A self-organizing map (SOM) neural network was developed from Argo gridded datasets in order to estimate a subsurface temperature anomaly (STA) from remote sensing data. The SOM maps were trained using anomalies of sea surface temperature (SST), height (SSH), and salinity (SSS) data from Argo gridded monthly anomaly datasets, labeled with Argo STA data from 2005 through 2010, which were then used to estimate the STAs at different depths in the North Atlantic from the sea surface data. The estimated STA maps and time series were compared with Argo STAs including independent datasets for validation. In the Gulf Stream path areas, the STA estimations from the SOM algorithm show good agreement with in situ measurements taken from the surface down to 700-m depth, with a correlation coefficient larger than 0.8. Sensitivity of the SOM, when including salinity, shows that with SSS anomaly data in the SOM training process reveal the importance of SSS information, which can improve the estimation of STA in the subtropical ocean by up to 30%. In subpolar basins, the monthly climatology SST and SSH can also help to improve the estimation by as much as 40%. The STA time series for 1993–2004 in the midlatitude North Atlantic were estimated from remote sensing SST and altimetry time series using the SOM algorithm. Limitations for the SOM algorithm and possible error sources in the estimation are briefly discussed.

scholarly journals Predictability of the Barents Sea Ice in Early Winter: Remote Effects of Oceanic and Atmospheric Thermal Conditions from the North Atlantic

2014 ◽  
Vol 27 (23) ◽  
pp. 8884-8901 ◽  
Author(s):  
Takuya Nakanowatari ◽  
Kazutoshi Sato ◽  
Jun Inoue
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Barents Sea ◽  
Temperature Anomaly ◽  
Early Winter ◽  
Subsurface Temperature ◽  
The North ◽  
The Barents Sea ◽  
Subsurface Temperature Anomaly ◽  
The North Atlantic

Abstract Predictability of sea ice concentrations (SICs) in the Barents Sea in early winter (November–December) is studied using canonical correlation analysis with atmospheric and ocean anomalies from the NCEP Climate Forecast System Reanalysis (CFSR) data. It is found that the highest prediction skill for a single-predictor model is obtained from the 13-month lead subsurface temperature at 200-m depth (T200) and the in-phase meridional surface wind (Vsfc). T200 skillfully predicts SIC variability in 35% of the Barents Sea, mainly in the eastern side. The T200 for negative sea ice anomalies exhibits warm anomalies in the subsurface ocean temperature downstream of the Norwegian Atlantic Slope Current (NwASC) on a decadal time scale. The diagnostic analysis of NCEP CFSR data suggests that the subsurface temperature anomaly stored below the thermocline during summer reemerges in late autumn by atmospheric cooling and affects the sea ice. The subsurface temperature anomaly of the NwASC is advected from the North Atlantic subpolar gyre over ~3 years. Also, Vsfc skillfully predicts SIC variability in 32% of the Barents Sea, mainly in the western side. The Vsfc for the negative sea ice anomalies exhibits southerly wind anomalies; Vsfc is related to the large-scale atmospheric circulation patterns from the subtropical North Atlantic to the Eurasian continent. This study suggests that both atmospheric and oceanic remote effects have a potential impact on the forecasting accuracy of SIC.

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.

Impact of Great Salinity Anomalies on the Low-Frequency Variability of the North Atlantic Climate

2006 ◽  
Vol 19 (3) ◽  
pp. 470-482 ◽  
Author(s):  
Rong Zhang ◽  
Geoffrey K. Vallis
Keyword(s):  
Surface Temperature ◽  
North Atlantic ◽  
Temperature Anomaly ◽  
Low Frequency ◽  
Sea Surface ◽  
The North ◽  
Sea Surface Temperature Anomaly ◽  
Salinity Anomaly ◽  
Great Salinity Anomaly ◽  
The North Atlantic

Abstract In this paper, it is shown that coherent large-scale low-frequency variabilities in the North Atlantic Ocean—that is, the variations of thermohaline circulation, deep western boundary current, northern recirculation gyre, and Gulf Stream path—are associated with high-latitude oceanic Great Salinity Anomaly events. In particular, a dipolar sea surface temperature anomaly (warming off the U.S. east coast and cooling south of Greenland) can be triggered by the Great Salinity Anomaly events several years in advance, thus providing a degree of long-term predictability to the system. Diagnosed phase relationships among an observed proxy for Great Salinity Anomaly events, the Labrador Sea sea surface temperature anomaly, and the North Atlantic Oscillation are also discussed.

scholarly journals Daily scale wintertime sea surface temperature and IPC-Navidad variability in the southern Bay of Biscay from 1981 to 2010

Ocean Science ◽  
2013 ◽  
Vol 9 (4) ◽  
pp. 655-679 ◽  
Author(s):  
G. Esnaola ◽  
J. Sáenz ◽  
E. Zorita ◽  
A. Fontán ◽  
V. Valencia ◽  
...  
Keyword(s):  
Time Series ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North Atlantic ◽  
Sea Surface ◽  
Bay Of Biscay ◽  
Surface Level ◽  
The North ◽  
Daily Scale ◽  
The North Atlantic

Abstract. The combination of remotely sensed gappy Sea surface temperature (SST) images with the missing data filling DINEOF (data interpolating empirical orthogonal functions) technique, followed by a principal component analysis of the reconstructed data, has been used to identify the time evolution and the daily scale variability of the wintertime surface signal of the Iberian Poleward Current (IPC), or Navidad, during the 1981–2010 period. An exhaustive comparison with the existing bibliography, and the vertical temperature and salinity profiles related to its extremes over the Bay of Biscay area, show that the obtained time series accurately reflect the IPC-Navidad variability. Once a time series for the evolution of the SST signal of the current over the last decades is well established, this time series is used to propose a physical mechanism in relation to the variability of the IPC-Navidad, involving both atmospheric and oceanic variables. According to the proposed mechanism, an atmospheric circulation anomaly observed in both the 500 hPa and the surface levels generates atmospheric surface level pressure, wind-stress and heat-flux anomalies. In turn, those surface level atmospheric anomalies induce mutually coherent SST and sea level anomalies over the North Atlantic area, and locally, in the Bay of Biscay area. These anomalies, both locally over the Bay of Biscay area and over the North Atlantic, are in agreement with several mechanisms that have separately been related to the variability of the IPC-Navidad, i.e. the south-westerly winds, the joint effect of baroclinicity and relief (JEBAR) effect, the topographic β effect and a weakened North Atlantic gyre.

scholarly journals Space-Time Sea Surface pCO2 Estimation in the North Atlantic Based on CatBoost

2021 ◽  
Vol 13 (14) ◽  
pp. 2805
Author(s):  
Hongwei Sun ◽  
Junyu He ◽  
Yihui Chen ◽  
Boyu Zhao
Keyword(s):  
North Atlantic ◽  
Function Analysis ◽  
Biological Activities ◽  
Mixed Layer Depth ◽  
Sea Surface ◽  
Coefficient Of Determination ◽  
Mean Bias Error ◽  
Bias Error ◽  
The North ◽  
The North Atlantic

Sea surface partial pressure of CO2 (pCO2) is a critical parameter in the quantification of air–sea CO2 flux, which plays an important role in calculating the global carbon budget and ocean acidification. In this study, we used chlorophyll-a concentration (Chla), sea surface temperature (SST), dissolved and particulate detrital matter absorption coefficient (Adg), the diffuse attenuation coefficient of downwelling irradiance at 490 nm (Kd) and mixed layer depth (MLD) as input data for retrieving the sea surface pCO2 in the North Atlantic based on a remote sensing empirical approach with the Categorical Boosting (CatBoost) algorithm. The results showed that the root mean square error (RMSE) is 8.25 μatm, the mean bias error (MAE) is 4.92 μatm and the coefficient of determination (R2) can reach 0.946 in the validation set. Subsequently, the proposed algorithm was applied to the sea surface pCO2 in the North Atlantic Ocean during 2003–2020. It can be found that the North Atlantic sea surface pCO2 has a clear trend with latitude variations and have strong seasonal changes. Furthermore, through variance analysis and EOF (empirical orthogonal function) analysis, the sea surface pCO2 in this area is mainly affected by sea temperature and salinity, while it can also be influenced by biological activities in some sub-regions.

The North Atlantic atmosphere-sea surface 14C gradient during the Younger Dryas climatic event

1994 ◽  
Vol 126 (4) ◽  
pp. 275-287 ◽  
Author(s):  
Edouard Bard ◽  
Maurice Arnold ◽  
Jan Mangerud ◽  
Martine Paterne ◽  
Laurent Labeyrie ◽  
...  
Keyword(s):  
North Atlantic ◽  
Younger Dryas ◽  
Sea Surface ◽  
The North ◽  
Climatic Event ◽  
The North Atlantic

Meridional Tripole Mode of Winter Precipitation over the Arctic and Continental North Africa–Eurasia

2021 ◽  
pp. 1
Author(s):  
Xiaolin Liu ◽  
Jianhua Lu ◽  
Yimin Liu ◽  
Guoxiong Wu
Keyword(s):  
Time Series ◽  
North Africa ◽  
North Atlantic ◽  
Hadley Cell ◽  
The Arctic ◽  
Positive Phase ◽  
The North ◽  
Ferrel Cell ◽  
The North Atlantic ◽  
Westerly Jets

AbstractWintertime precipitation is vital to the growth of glaciers in the northern hemisphere. We find a tripole mode of precipitation (PTM), with each pole of the mode extending zonally over the eastern hemisphere roughly between 30°W and 120°E, and the positive/negative/positive structure for its positive phase extending meridionally from the Arctic to the continental North Africa–Eurasia. The large-scale dynamics associated with the PTM is explored. The positive phase of the PTM is associated with the negative while eastward-shifted phase of the North Atlantic Oscillation (NAO) and a zonal band of positive SST anomaly in the tropics, together with a narrowed Hadley cell and weakened Ferrel cell. While being north-eastward tilted and separated from their North Africa-Eurasia counterpart in the climatological mean, the upper-tropospheric westerly jets over the east Pacific and north Atlantic become extending zonally and shifting southward and hence form a circumpolar subtropical jet as a whole by connecting with the westerly jets over the North Africa-Eurasia. The enhanced zonal winds over the north Atlantic promote more synoptic-scale transient eddies which are waveguided by the jet streams. The polar vortex weakens and cold air dips southward from the North Pole. Further diagnosis of the E-vectors suggests that transient eddies have a positive feedback on the weakening of Ferrel cell. Opposite features are associated with the negative phase of the PTM. The reconstructed time series using multiple linear regression on the NAO index and the tropical SST averaged over 20°S– 20°N, can explain 62.4% of the variance of the original the original precipitation time series.

Climate Response to External Sources of Freshwater: North Atlantic versus the Southern Ocean

2007 ◽  
Vol 20 (3) ◽  
pp. 436-448 ◽  
Author(s):  
Ronald J. Stouffer ◽  
Dan Seidov ◽  
Bernd J. Haupt
Keyword(s):  
Southern Ocean ◽  
Southern Hemisphere ◽  
North Atlantic ◽  
Surface Waters ◽  
Real World ◽  
The Other ◽  
Sea Surface ◽  
The North ◽  
The North Atlantic ◽  
The Antarctic

Abstract The response of an atmosphere–ocean general circulation model (AOGCM) to perturbations of freshwater fluxes across the sea surface in the North Atlantic and Southern Ocean is investigated. The purpose of this study is to investigate aspects of the so-called bipolar seesaw where one hemisphere warms and the other cools and vice versa due to changes in the ocean meridional overturning. The experimental design is idealized where 1 Sv (1 Sv ≡ 106 m3 s−1) of freshwater is added to the ocean surface for 100 model years and then removed. In one case, the freshwater perturbation is located in the Atlantic Ocean from 50° to 70°N. In the second case, it is located south of 60°S in the Southern Ocean. In the case where the North Atlantic surface waters are freshened, the Atlantic thermohaline circulation (THC) and associated northward oceanic heat transport weaken. In the Antarctic surface freshening case, the Atlantic THC is mainly unchanged with a slight weakening toward the end of the integration. This weakening is associated with the spreading of the fresh sea surface anomaly from the Southern Ocean into the rest of the World Ocean. There are two mechanisms that may be responsible for such weakening of the Atlantic THC. First is that the sea surface salinity (SSS) contrast between the North Atlantic and North Pacific is reduced. And, second, when freshwater from the Southern Ocean reaches the high latitudes of the North Atlantic Ocean, it hinders the sinking of the surface waters, leading to the weakening of the THC. The spreading of the fresh SSS anomaly from the Southern Ocean into the surface waters worldwide was not seen in earlier experiments. Given the geography and climatology of the Southern Hemisphere where the climatological surface winds push the surface waters northward away from the Antarctic continent, it seems likely that the spreading of the fresh surface water anomaly could occur in the real world. A remarkable symmetry between the two freshwater perturbation experiments in the surface air temperature (SAT) response can be seen. In both cases, the hemisphere with the freshwater perturbation cools, while the opposite hemisphere warms slightly. In the zonally averaged SAT figures, both the magnitude and the pattern of the anomalies look similar between the two cases. The oceanic response, on the other hand, is very different for the two freshwater cases, as noted above for the spreading of the SSS anomaly and the associated THC response. If the differences between the atmospheric and oceanic responses apply to the real world, then the interpretation of paleodata may need to be revisited. To arrive at a correct interpretation, it matters whether or not the evidence is mainly of atmospheric or oceanic origin. Also, given the sensitivity of the results to the exact details of the freshwater perturbation locations, especially in the Southern Hemisphere, a more realistic scenario must be constructed to explore these questions.

Sign in / Sign up

Export Citation Format

Share Document