Ocean temperatures and sea level

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Recent sea surface temperature 

Sea surface temperatures 27 June 2015 (degrees C). White areas represents land areas. Map source: NCEP. Technical notes on the production of the map are available here. Please use this link if you want to see the original figure or want to check for a more recent update than shown above.

Sea surface temperature anomalies 27 June 2015 (degrees C). This map shows the current anomaly (deviation from normal) of the surface temperature of Earth's oceans. White represents land areas. White shows the extent of sea ice. Map source: NCEP. Technical notes on the production of the map are available here. Please use this link if you want to see the original figure or want to check for a more recent update than shown above.

 

Arctic sea surface temperatures 27 June 2015 (degrees C). White areas represents land areas. Map source: NCEP. Technical notes on the production of the map are available here. Please use this link if you want to see the original figure or want to check for a more recent update than shown above.

Arctic sea surface temperature anomalies 27 June 2015 (degrees C). This map shows the current anomaly (deviation from normal) of the sea surface temperature within the region shown. White areas represents land areas. Map source: NCEP. Technical notes on the production of the map are available here. Please use this link if you want to see the original figure or want to check for a more recent update than shown above.

 

 

Sea surface temperature variations since January 1983 across the Indian and Pacific Ocean, between 3.5 degrees north and south of Equator. The west-east transect shown covers the area between the east coast of Africa and the west coast of South America. Diagram source: NOAA/ESRL. Please use this link if you want to see the original figure or want to check for a more recent update than shown above. Last day shown: 9 June 2015.

 

 

Arctic and North Atlantic sea surface temperature 28 June 2015 (degrees C), according to the Centre for Ocean and Ice at the Danish Meteorological Institute (DMI). This map shows the current sea surface temperature (SST) to the left, and the anomaly (deviation from the average of the reference period) to the right. White areas represents the current sea ice cover. Grey areas are land areas. Reference period: 1961-1990. Please use this link if you want to see the original figures or want to check for more recent updates than shown above.

 

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Sea surface temperatures

Global monthly average lower troposphere temperature above oceans since 1979, according to University of Alabama at Huntsville, USA. The thick line is the simple running 37 month average, nearly corresponding to a running 3 yr average. Reference period 1981-2010. Agenta line is the running 37-month average of Argo float measurements, shown for comparison. Last month shown: May 2015. Last diagram update: 23 June 2015.

  • Click here to download the entire series of UAH MSU global monthly lower troposphere temperatures since December 1978.

  • Click here to read about data smoothing.

  • Click here or here to see more Argo-measurements.

 

Global monthly average sea surface temperature (SST) since 1979 according to University of East Anglia's Climatic Research Unit (CRU), UK. The data series (HadSST2) are described by Ranier et al. (2006). Base period: 1961-1990. The thick line is the simple running 37 month average, nearly corresponding to a running 3 yr average. Agenta line is the running 37-month average of Argo float measurements, shifted +0.2 degrees for easy comparison. Last month shown: May 2015. Last diagram update: 23 June 2015.

  • Click here or here to download the entire HadSST3 temperature series since 1850.

  • Click here or here to download the entire HadSST2 temperature series since 1850.

  • Click here to read a description of the data file format.

  • Click here to read about data smoothing.

  • Click here or here to see more Argo-measurements.

 

Global monthly average sea surface temperature (SST) since 1979 according to the National Climatic Data Center (NCDC), USA. Base period: 1901-2000. The thick line is the simple running 37 month average, nearly corresponding to a running 3 yr average. Agenta line is the running 37-month average of Argo float measurements, shifted +0.2 degrees for easy comparison. Last month shown: May 2015. Last diagram update: 23 June 2015.

  • Click here to download the entire NCDC SST temperature series since 1880.

  • Click here to read a description of the data types used for producing the NCDC SST data series.

  • Click here to read about data smoothing.

  • Click here or here to see more Argo-measurements.

June 18, 2015: NCDC has introduced a number of rather large administrative changes to their sea surface temperature record. The overall result is to produce a record giving the impression of a continuous temperature increase, also in the 21st century. As the oceans cover about 71% of the entire surface of planet Earth, the effect of this administrative change is clearly seen in the NCDC record for global air temperature. The comparison with the Argo data (magenta line) show that the latest NCDC administrative change unfortunately resulted in an inferior record, compared to the previous (May 2015) version.

 

Coverage map for sea surface temperatures shown in the four diagrams below.

 

 

Global monthly sea surface temperature (SST) in the Tropics (10oN-10oS, 0-360o) since 1979 according to the National Oceanographic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC). The geographical sampling area is shown in map above as 'Tropics'. The thick line is the simple running 37 month average, nearly corresponding to a running 3 yr average. The warming period directly influenced by the 1998 El Niño is clearly visible. The data series goes back to January 1950. Here it is shown since 1979, to enable easy comparison with air the global temperature estimates shown above. Reference period: 1981-2010. Last month shown: May 2015. Last diagram update: 4 June 2015.

  • Click here to download the entire series of NOAA CPC monthly sea surface temperatures since January 1950.

  • Click here to read about data smoothing.

 

Global monthly sea surface temperature (SST) in the North Atlantic (5o-20oN, 30-60oW) since 1979 according to the National Oceanographic and Atmospheric Administration (NOAA) Climate Prediction Center. The geographical sampling area is shown in map above as 'N.Atl'. The thick line is the simple running 37 month average, nearly corresponding to a running 3 yr average. The data series goes back to January 1950. Here it is shown since 1979, to enable easy comparison with air the global temperature estimates shown above. Reference period: 1981-2010. Last month shown: May 2015. Last diagram update: 4 June 2015.

  • Click here to download the entire series of NOAA CPC monthly sea surface temperatures since January 1950.

  • Click here to read about data smoothing.

 

 

Global monthly sea surface temperature (SST) in the South Atlantic (0-20oS, 30oW-10oE) since 1979 according to the National Oceanographic and Atmospheric Administration (NOAA) Climate Prediction Center. The geographical sampling area is shown in map above as 'S.Atl'. The thick line is the simple running 37 month average, nearly corresponding to a running 3 yr average. The data series goes back to January 1950. Here it is shown since 1979, to enable easy comparison with air the global temperature estimates shown above. Reference period: 1981-2010. Last month shown: May 2015. Last diagram update: 4 June 2015.

  • Click here to download the entire series of NOAA CPC monthly sea surface temperatures since January 1950.

  • Click here to read about data smoothing.

 

 

Global monthly sea surface temperature (SST) in the Niño 3.4 region (5oN-5oS, 17oW-120oW) of the central Pacific Ocean since 1979 according to the National Oceanographic and Atmospheric Administration (NOAA) Climate Prediction Center. The geographical sampling area is shown in map above as 'Niño 3.4'. The thick line is the simple running 37 month average, nearly corresponding to a running 3 yr average. The data series goes back to January 1950. Here it is shown since 1979, to enable easy comparison with air the global temperature estimates shown above. Last month shown: May 2015. Last diagram update: 4 June 2015.

  • Click here to download the entire series of NOAA CPC monthly sea surface temperatures since January 1950.

  • Click here to read about data smoothing.

 

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Tropical sea surface temperature and global surface air temperature

Global monthly sea surface temperature (red) in the Tropics (10oN-10oS, 0-360o) since January 1950 according to the National Oceanographic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC). The geographical sampling area is shown in map above as 'Tropics'. Global monthly average surface air temperature (blue) since January 1950 according to Hadley CRUT, a cooperative effort between the Hadley Centre for Climate Prediction and Research and the University of East Anglia's Climatic Research Unit (CRU), UK. Base period for the NOAA series is 1971-2000, while the HadCRUT3 series uses 1961-1990 as base period. Last month shown: September 2014. Last diagram update: 28 October 2014.

 

The relation the global surface air temperature (HadCRUT3) and the tropical sea surface temperature (NOAA) shown in the diagram above is interesting. The offset between the two data series is due to the different base periods adopted, but in general the two data series tend to follow each other, without the general offset growing or decreasing since 1950.

Typically, 1-5 yr variations in the sea surface temperature have a larger amplitude than the corresponding variations in global surface air temperature. In addition, quite often a change in sea surface temperature appears to be initiated 1-3 months before the corresponding change in surface air temperature. In such cases, the temperature in the lower atmosphere appears to be controlled by change in sea surface temperatures, and not the other way around. Oceanographic processes such as, e.g., upwelling of warm or cold water masses might one obvious explanation. Another explanation might be variations in the amount of direct short wave solar radiation reaching the ocean surface. Whatever the control, the above diagram suggests that the tropical oceans are important for understanding global surface air temperature changes.

The apparent significance of the tropical oceans between 10oN and 10oS for the global surface air temperature is not entirely surprising. About 80% of the planet surface is covered by oceans between 10oN and 10oS, so the surface area covered by oceans is huge in this sector of the planet. Presumably the explanation for the significance of these tropical oceans is therefore relatively straight forward: The huge ocean surface in the Tropics is nearly perpendicular to the incoming direct solar radiation at daytime. Little of the direct short wave radiation reaching the ocean is therefore reflected, and the amount of absorbed solar radiation is essentially controlled by the tropical cloud cover. Variations in the tropical cloud cover may therefore be expected to represent an important control on the global surface air temperature, along with oceanographic phenomena (upwelling, etc.) within the tropical regions. 

 

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Ocean 0-2000m depth temperature summary

Diagram showing average 0-2000m depth ocean temperatures in selected latitudinal bands, using Argo-data. The thin line shows monthly values and the thick line shows the running 13-month average. Source: Global Marine Argo Atlas. Latest month shown: January 2015. Last diagram update: 23 June 2015.

  • Acknowledment and additional information: Roemmich, D. and J. Gilson, 2009. The 2004-2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Progress in Oceanography, 82, 81-100.

 

 

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Oceanic average temperature 0-100 m depth

World Oceans vertical average temperature 0-100 m depth since 1955. The thin line indicate 3-month values, and the thick line represents the simple running 39-month (c. 3 year) average. Data source: NOAA National Oceanographic Data Center (NODC). Base period 1955-2010. Last period shown: January-March 2015. Last diagram update 23 May 2015.

  • Click here to download the entire series of three-monthly oceanic temperature anomalies since January-March 1955.

  • Click here to read about data smoothing.

 

 

Pacific Ocean vertical average temperature 0-100 m depth since 1955. The thin line indicate 3-month values, and the thick line represents the simple running 39- month (c. 3 year) average. Data source: NOAA National Oceanographic Data Center (NODC). Base period 1955-2010.  Last period shown: January-March 2015. Last diagram update 23 May 2015.

  • Click here to download the entire series of three-monthly oceanic temperature anomalies since January-March 1955.

  • Click here to read about data smoothing.

 

 

Atlantic Ocean vertical average temperature 0-100 m depth since 1955. The thin line indicate 3-month values, and the thick line represents the simple running 39- month (c. 3 year) average. Data source: NOAA National Oceanographic Data Center (NODC). Base period 1955-2010.  Last period shown: January-March 2015. Last diagram update 23 May 2015.

  • Click here to download the entire series of three-monthly oceanic temperature anomalies since January-March 1955.

  • Click here to read about data smoothing.

 

 

 

Indian Ocean vertical average temperature 0-100 m depth since 1955. The thin line indicate 3-month values, and the thick line represents the simple running 39- month (c. 3 year) average. Data source: NOAA National Oceanographic Data Center (NODC). Base period 1955-2010.  Last period shown: January-March 2015. Last diagram update 23 May 2015.

  • Click here to download the entire series of three-monthly oceanic temperature anomalies since January-March 1955.

  • Click here to read about data smoothing.

 

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Global oceanic temperature anomaly 0-700 m depth

 

World Oceans vertical average temperature 0-700 m depth since 1979. The thin line indicate 3-month values, and the thick line represents the simple running 39-month (c. 3 year) average. Data source: NOAA National Oceanographic Data Center (NODC). Base period 1955-2010. Last period shown: January-March 2015. Last diagram update 23 May 2015.

  • Click here to download the entire series of three-monthly oceanic temperature anomalies since January-March 1955.

  • Click here to read about data smoothing.

 

World Oceans vertical average temperature 0-700 m depth since 1955. The thin line indicate 3-month values, and the thick line represents the simple running 39-month (c. 3 year) average. Data source: NOAA National Oceanographic Data Center (NODC). Base period 1955-2010. Last period shown: January-March 2015. Last diagram update 23 May 2015.

  • Click here to download the entire series of three- monthly oceanic temperature anomalies since January-March 1955.

  • Click here to read about data smoothing.

 

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Global ocean temperatures from surface to 2000 m depth

Diagram showing global ocean temperatures at selected depths, using Argo-data. The thin line shows monthly values and the thick line shows the running 13-month average. Source: Global Marine Argo Atlas. Latest month shown: January 2015. Last diagram update: 23 June 2015.

  • Acknowledment and additional information: Roemmich, D. and J. Gilson, 2009. The 2004-2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Progress in Oceanography, 82, 81-100.

 

 

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Circum-arctic ocean temperatures from surface to 2000 m depth

Diagram showing circum-arctic ocean temperatures at selected depths, using Argo-data. The thin line shows monthly values and the thick line shows the running 13-month average. Source: Global Marine Argo Atlas. Latest month shown: January 2015. Last diagram update: 23 June 2015.

  • Acknowledment and additional information: Roemmich, D. and J. Gilson, 2009. The 2004-2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Progress in Oceanography, 82, 81-100.

 

 

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Circum-equator ocean temperatures from surface to 2000 m depth

Diagram showing circum-equator ocean temperatures at selected depths, using Argo-data. The thin line shows monthly values and the thick line shows the running 13-month average. Source: Global Marine Argo Atlas. Latest month shown: January 2015. Last diagram update: 23 June 2015.

  • Acknowledment and additional information: Roemmich, D. and J. Gilson, 2009. The 2004-2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Progress in Oceanography, 82, 81-100.

 

 

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Circum-antarctic ocean temperatures from surface to 2000 m depth

Diagram showing circum-antarctic ocean temperatures at selected depths, using Argo-data. The thin line shows monthly values and the thick line shows the running 13-month average. Source: Global Marine Argo Atlas. Latest month shown: January 2015. Last diagram update: 23 June 2015.

  • Acknowledment and additional information: Roemmich, D. and J. Gilson, 2009. The 2004-2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Progress in Oceanography, 82, 81-100.

 

 

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North Atlantic (60-0W, 30-65N) heat content 0-700 m depth

Map showing the North Atlantic area within 60-0W and 30-65N, for which the heat content within the uppermost 700 m is shown in the two diagrams below.

 

 

Global monthly heat content anomaly (GJ/m2) in the uppermost 700 m of the North Atlantic (60-0W, 30-65N) ocean since January 1979. The thin line indicate monthly values, and the thick line represents the simple running 37 month (c. 3 year) average. The starting month (January 1979) is chosen to enable easy comparison with global air temperature estimates within the satellite period. Data source: National Oceanographic Data Center (NODC). Last period shown: January-March 2015. Last diagram update 4 June 2015.

 

 

Global monthly heat content anomaly (GJ/m2) in the uppermost 700 m of the North Atlantic (60-0W, 30-65N) ocean since January 1955. The thin line indicate monthly values, and the thick line represents the simple running 37 month (c. 3 year) average. Data source: National Oceanographic Data Center (NODC). Last period shown: January-March 2015. Last diagram update 4 June 2015.

 

 

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North Atlantic 59 N transect to 2000 m depth

Depth-temperature diagram along 59 N across the North Atlantic, extending from northern Labrador in the west to northern Scotland in the east, using Argo-data. The uppermost panel shows the temperature, and the lower diagram shows the temperature anomaly, using the monthly average temperature 2004-2013 as reference. Source: Global Marine Argo Atlas. Latest month shown: January 2015. Last diagram update: 23 June 2015.

  • Acknowledment and additional information: Roemmich, D. and J. Gilson, 2009. The 2004-2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Progress in Oceanography, 82, 81-100.

  • Upper panel in the above diagrams shows the main North Atlantic Current in this transect to be located between 30W and 0W, at 0-800 m depth. See diagram below to se a time series since January 2004 for this part of the transect.

 

 

Average temperature along 59 N, 30-0W, 0-800m depth, corresponding to the main part of the North Atlantic Current, using Argo-data. Source: Global Marine Argo Atlas. Latest month shown: January 2015. Last diagram update: 23 June 2015.

  • Acknowledment and additional information: Roemmich, D. and J. Gilson, 2009. The 2004-2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Progress in Oceanography, 82, 81-100

 

 

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Arctic gateway seas (20W-40E. 70-80N) heat content 0-700 m depth

Map showing the Arctic Gateway Seas within 20W-40E and 70-80N, for which the heat content within the uppermost 700 m is shown in the three diagrams below.

 

 

Global monthly heat content anomaly (GJ/m2) in the uppermost 700 m of the East Greenland Sea (20-0W, 70-80N) since January 1955. The thin line indicate monthly values, and the thick line represents the simple running 37 month (c. 3 year) average. These data may be compared with Arctic sea ice variations. Data source: National Oceanographic Data Center (NODC). Last period shown: January-March 2015. Last diagram update 4 June 2015.

  • Click here to download the entire series of monthly oceanic heat content anomalies since January 1955 (select heat content 1955-now).

  • Click here to read about data smoothing.

 

 

Global monthly heat content anomaly (GJ/m2) in the uppermost 700 m of the West Svalbard Sea (0-20E, 70-80N) since January 1955. The thin line indicate monthly values, and the thick line represents the simple running 37 month (c. 3 year) average. These data may be compared with Arctic sea ice variations and Svalbard surface air temperatures. Data source: National Oceanographic Data Center (NODC). Last period shown: January-March 2015. Last diagram update 4 June 2015.

  • Click here to download the entire series of monthly oceanic heat content anomalies since January 1955 (select heat content 1955-now).

  • Click here to read about data smoothing.

 

 

Global monthly heat content anomaly (GJ/m2) in the uppermost 700 m of the western Barents Sea (20-40E, 70-80N) since January 1955. The thin line indicate monthly values, and the thick line represents the simple running 37 month (c. 3 year) average. These data may be compared with Arctic sea ice variations and Svalbard surface air temperatures. Data source: National Oceanographic Data Center (NODC). Last period shown: January-March 2015. Last diagram update 4 June 2015.

  • Click here to download the entire series of monthly oceanic heat content anomalies since January 1955 (select heat content 1955-now).

  • Click here to read about data smoothing.

 

 

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Average sea temperatures in the upper 300 m at Equator in the Pacific

Location map showing the central Pacific Ocean with location of measurement areas shown in the three diagrams below.

 

Monthly average temperatures in the uppermost 300 m of the Pacific Ocean between 130oE and 80oW according to the NOAA Climate Prediction Center.  For geographical location of transect please see map above. The thin line indicate monthly values, and the thick line is the simple running 7 year average. Reference period: 1981-2010. Last month shown: May 2015. Last diagram update: 4 June 2015.

  • Click here to download the entire series of monthly average temperatures since February 1979.

  • Click here for additional information.

  • Click here to read about data smoothing.

 

Monthly average temperatures in the uppermost 300 m of the Pacific Ocean between 160oE and 80oW according to the NOAA Climate Prediction Center.  For geographical location of transect please see map above. The thin line indicate monthly values, and the thick line is the simple running 7 year average. Reference period: 1981-2010. Last month shown: May 2015. Last diagram update: 4 June 2015.

  • Click here to download the entire series of monthly average temperatures since February 1979.

  • Click here for additional information.

  • Click here to read about data smoothing.

 

Monthly average temperatures in the uppermost 300 m of the Pacific Ocean between 160oW and 80oW according to the NOAA Climate Prediction Center.  For geographical location of transect please see map above. The thin line indicate monthly values, and the thick line is the simple running 7 year average. Reference period: 1981-2010. Last month shown: May 2015. Last diagram update: 4 June 2015.

  • Click here to download the entire series of monthly average temperatures since February 1979.

  • Click here for additional information.

  • Click here to read about data smoothing.

 

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PDO - Pacific Decadal Oscillation

Typical wintertime Sea Surface Temperature (colors),Sea Level Pressure (black lines) and surface windstress (arrows) anomaly patterns during warm and cool phases of PDO. Figure source: Joint Institute for the Study of the Atmosphere and Ocean (JISAO), a Cooperative Institute between the National Oceanic and Atmospheric Administration and the University of Washington.

 

Annual values of the Pacific Decadal Oscillation (PDO) according to the Joint Institute for the Study of the Atmosphere and Ocean (JISAO), a Cooperative Institute between the National Oceanic and Atmospheric Administration and the University of Washington. The PDO is a long-lived El Niño-like pattern of Pacific climate variability, and the data series goes back to January 1900. Causes for PDO are not currently known, but even in the absence of a theoretical understanding, PDO climate information improves season-to-season and year-to-year climate forecasts for North America because of its strong tendency for multi-season and multi-year persistence. The PDO also appears to be roughly in phase with global temperature changes. Thus, from a societal impacts perspective, recognition of PDO is important because it shows that "normal" climate conditions can vary over time periods comparable to the length of a human's lifetime. Base period: 1982-2002. The thin line indicate annual PDO values, and the thick line is the simple running 7 year average. Last year shown: 2014. Last diagram update 20 January 2015.

  • Click here to download the entire series of monthly PDO index values since January 1900.

  • Click here to read about data smoothing.

 

 

Monthly values of the Pacific Decadal Oscillation (PDO) according to the Joint Institute for the Study of the Atmosphere and Ocean (JISAO), a Cooperative Institute between the National Oceanic and Atmospheric Administration and the University of Washington. The PDO is a long-lived El Niño-like pattern of Pacific climate variability, and the data series goes back to January 1900. Base period: 1982-2002. The thin line indicate monthly PDO values, and the thick line is the simple running 37 month average. Here the PDO data are shown since 1979, to enable easy comparison with air the global temperature estimates shown elsewhere. Last month shown: April 2015. Last diagram update: 4 June 2015.

  • Click here to download the entire series of monthly PDO index values since January 1900.

  • Click here to read about data smoothing.

 

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La Niña and El Niño episodes

 

Warm (>+0.5oC; red stippled line) and cold (<0.5oC; blue stippled line) episodes for the Oceanic Niño Index (ONI), defined as 3 month running mean of ERSST.v3b SST anomalies in the Niño 3.4 region (5oN-5oS, 120o-170oW)]. Base period: 1971-2000. For historical purposes cold and warm episodes are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons. The thin line indicates 3 month average values, and the thick line is the simple running 7 year average of these. Last 3 month running mean shown: February-April 2015. Last diagram update 5 May 2015.

  • Click here to download the entire series of the Oceanic Niño Index (ONI) since December 1949 - February 1950.

  • Click here to read about data smoothing.

 

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AMO (Atlantic Multidecadal Oscillation) Index

 

The Atlantic Multidecadal Oscillation (AMO) is a mode of variability occurring in the North Atlantic Ocean sea surface temperature field, identified by Schlesinger and Ramankutty in 1994. The AMO is basically an index of North Atlantic sea surface temperatures (SST).

The AMO index appears to be correlated to air temperatures and rainfall over much of the Northern Hemisphere. The association appears to be high for  North Eastern Brazil, African Sahel rainfall and North American and European summer climate. The AMO index also appears to be associated with changes in the frequency of North American droughts and is reflected in the frequency of severe Atlantic hurricanes.

As one example, the AMO index may be related to the past occurrence of major droughts in the US Midwest and the Southwest. When the AMO is high, these droughts tend to be more frequent or prolonged, and vice-versa for low values of AMO. Two of the most severe droughts of the 20th century in US occurred during the peak AMO values between 1925 and 1965: The Dust Bowl of the 1930s and the 1950s drought. On the other hand Florida and the Pacific Northwest tend to be the opposite; high AMO is associated with relatively high precipitation.

In the diagrams below only originally (raw) AMO values is shown. As is seen from the annual diagram, the AMO index has been increasing since the beginning of the record in 1856, although with a clear about 60 yr long variation superimposed. Often AMO values are shown linearly detrended to remove the overall increase since 1856, to emphasise the apparent rhythmic 60 yr variation.  This detrending is usually intended to remove the alleged influence of greenhouse gas-induced global warming from the analysis, believed to cause the overall increase. However, as is seen in the diagram below, the overall increase has taken place since at least 1856, long before the alleged strong influence of increasing atmospheric CO2 began around 1975 (IPCC 2007). Therefore the overall increase is likely to have another explanation; it may simply represent a natural recovery since the end of the previous cold period (the Little Ice Age). If so, the general AMO increase since 1856 may well represent part of a longer natural variation, to long to be fully represented by the AMO data series since 1856. 

For the above reasons, only the original (not detrended) AMO values are shown in the two diagrams below:

 

Annual Atlantic Multidecadal Oscillation (AMO) index values since 1856. The thin line indicates 3 month average values, and the thick line is the simple running 11 year average. Further explanation in text above. Data source: Earth System Research Laboratory at NOAA. Last year shown: 2014. Last diagram update 20 January 2015.

  • Click here to download the entire series of the Atlantic Multidecadal Oscillation (AMO) index values since 1856 (choose unaltered data).

  • Click here to read about data smoothing.

 

 

Monthly Atlantic Multidecadal Oscillation (AMO) index values since January 1979. The thin line indicates 3 month average values, and the thick line is the simple running 11 year average. By choosing January 1979 as starting point, the diagram is easy to compare with other types of temperature diagrams covering the satellite period since 1979. Further explanation in text above. Data source: Earth System Research Laboratory at NOAA. Last month shown: April 2015. Last diagram update: 4 June 2015.

  • Click here to download the entire series of the Atlantic Multidecadal Oscillation (AMO) index values since 1856 (choose unaltered data).

  • Click here to read about data smoothing.

 

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Sea-level in general

Global (or eustatic) sea-level change is measured relative to an idealised reference level, the geoid, which is a mathematical model of planet Earth’s surface (Carter et al. 2014). Global sea-level is a function of the volume of the ocean basins and the volume of water they contain. Changes in global sea-level are caused by – but not limited to - four main mechanisms:

  1. Changes in local and regional air pressure and wind, and tidal changes introduced by the Moon. 

  2. Changes in ocean basin volume by tectonic (geological) forces. 

  3. Changes in ocean water density caused by variations in currents, water temperature and salinity. 

  4. Changes in the volume of water caused by changes in the mass balance of terrestrial glaciers.

1.   In addition to these there are other mechanisms influencing sea-level; such as storage of ground water, storage in lakes and rivers, evaporation, etc.

Mechanism 1 is controlling sea-level at many sites on a time scale from months to several years. As an example, many coastal stations show a pronounced annual variation reflecting seasonal changes in air pressures and wind speed. Longer-term climatic changes playing out over decades or centuries will also affect measurements of sea-level changes. Hansen et al. (2011, 2015) provide excellent analyses of sea-level changes caused by recurrent changes of the orbit of the Moon and other phenomena.

Mechanism 2 – with the important exception of earthquakes and tsunamis - typically operates over long (geological) time scales, and is not significant on human time scales. It may relate to variations in the sea-floor spreading rate, causing volume changes in mid-ocean mountain ridges, and to the slowly changing configuration of land and oceans. Another effect may be the slow rise of basins due to isostatic offloading by deglaciation after an ice age. The floor of the Baltic Sea and the Hudson Bay are presently rising, causing a slow net transfer of water from these basins into the adjoining oceans. Slow changes of very big glaciers (ice sheets) and movements in the mantle will affect the gravity field and thereby the vertical position of the ocean surface. Any increase of the total water mass as well as sediment deposition into oceans increase the load on their bottom, generating sinking by viscoelastic flow in the mantle below. The mantle flow is directed towards the sourrounding land areas, which will rise, thereby partly compensating for the initial sea level increase induced by the increased water mass in the ocean. 

Mechanism 3 (temperature-driven expansion) only affects the uppermost part of the oceans on human time scales. Usually, temperature-driven changes in density are more important than salinity-driven changes. Seawater is characterised by a relatively small coefficient of expansion, but the effect should however not be overlooked, especially when interpreting satellite altimetry data. Temperature-driven expansion of a column of seawater will not affect the total mass of water within the column considered, and will therefore not affect the potential at the top of the water column. Temperature-driven ocean water expansion will therefore not in itself lead to lateral displacement of water, but only lift the ocean surface locally. Near the coast, where people are living, the depth of water approaches zero, so no temperature-driven expansion will take place here (Mörner 2015). Mechanism 3 is for that reason not important for coastal regions.

Mechanism 4 (changes in glacier mass balance) is an important driver for global sea-level changes along coasts, for human time scales. Volume changes of floating glaciers – ice shelves – has no influence on the global sea-level, just like volume changes of floating sea ice has no influence. Only the mass-balance of grounded or land-based glaciers is important for the global sea-level along coasts.

Summing up: Mechanism 1 and 4 are the most important for understanding sea-level changes along coasts.

 

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Sea-level from tide-gauges

Tide-gauges are located directly at coastal sites, and record the net movement of the local ocean surface in relation to land. Local relative sea-level change is what counts for purposes of coastal planning, so tide-gauge data are directly applicable for planning purposes for coastal installations (Carter et al. 2014). In a more scientific context, the measured net movement of the local sea-level is composed of two local components: 1) The vertical change of the ocean surface, and 2) the vertical change of the land surface. If one of these is known, the other component can be calculated.

The tide-gauge data displayed below are all downloaded from the public access PSMSL Data Explorer. In order to construct time series of sea level measurements at each station, the monthly and annual means have to be reduced to a common datum. This reduction is performed by the PSMSL making use of the tide gauge datum history provided by the supplying authority. The Revised Local Reference (RLR) datum at each station is defined to be approximately 7000 mm below mean sea level, with this arbitrary choice made many years ago in order to avoid negative numbers in the resulting RLR monthly and annual mean values.

A selection of PSMSL-stations are displayed below, organised from north to south.

 

 

Ny-Ålesund (Svalbard) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

Note to the Ny-Ålesund sea-level record: At Ny-Ålesund the relative sea-level change since September 1976 is about -6.9 mm/yr, meaning that sea-level is falling almost 7 mm each year in relation to the land. At Ny-ålesund the real vertical land movement is recorded by the Geodetic Observatory since 1991. The present ground uplift rate is 5.6 ± 1.57 mm/yr (Mémin et al. 2011). Based on the sea-level observations since January 1992 (see diagram above) the present relative sea-level change is about -6.9 mm/yr.  From this the real modern eustatic sea-level change at western Spitsbergen can be calculated to be 5.6 - 6.9 = -1.3 mm/yr ± 1.57 mm/yr (at least).

 

 

 

Barentsburg (Svalbard) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Investia Tsik (Russia) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 24, 2015.

 

 

Tromsø (Norway) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 26, 2015.

 

 

Bergen (Norway) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 24, 2015.

 

 

 

Oslo (Norway) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Stockholm (Sweden) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Copenhagen (Denmark) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2012. Last diagram update: May 23, 2015.

 

 

Korsør (Denmark) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2012. Last diagram update: June 6, 2015.

 

 

 

Wismar (Germany) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Den Helder (Netherlands) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Vlissingen (Netherlands) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Newlyn (UK) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Brest (France) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

New York (USA) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Trieste (Italy) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Cascais (Portugal) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 1993. Last diagram update: May 23, 2015.

 

 

San Diego (USA) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Key West (USA) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

 

Honolulu (USA) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Balboa (Panama) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Maldives (Indian Ocean) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: March 2012. Last diagram update: May 23, 2015.

 

 

Montevideo (Uruguay) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: November 2013. Last diagram update: May 24, 2015.

 

 

 

 

Freemantle (Australia) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 23, 2015.

 

 

Sydney (Australia) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 1993. Last diagram update: May 24, 2015.

 

 

 

Aukland (New Zealand) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: May 2000. Last diagram update: May 23, 2015.

 

 

Argentine Islands (Antarctica) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 24, 2015.

 

 

Cape Roberts (Antarctica) monthly tide gauge data from PSMSL Data Explorer. The blue dots are the individual monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: July 2009. Last diagram update: May 24, 2015.

 

 

Holgate-9 monthly tide gauge data from PSMSL Data Explorer. Holgate (2007) suggested the nine stations listed in the diagram to capture the variability found in a larger number of stations over the last half century studied previously. For that reason average values of the Holgate-9 group of tide gauge stations are interesting to follow. The blue dots are the individual average monthly observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Last month shown: December 2013. Last diagram update: May 24, 2015.

 

 

 

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Sea-level from satellite altimetry  

Satellite altimetry is a new and valuable type of measurement, providing unique insight into the detailed surface topography of the oceans, and changes of this. However, it is not a precise tool for estimating changes in global sea level due to a number of assumptions made when interpreting the original satellite data. 

One of the assumptions made during the interpretation of satellite altimetry data is the amount of correction made locally and regionally for Glacial Isostatic Adjustment (GIA). GIA relate to large-scale, long-term mass transfer from the oceans to the land, in the form of rytmic waxing and waning of the large Quaternary ice sheets in North America and North Europe. This enormous mass transfer causes rytmic changes in surface load, resulting in viscoelastic mantle flow and elastic effects in the upper crust. No single technique or observational network are able to give enough information on all aspects and consequences of GIA, wherefore the assumptions adopted for the interpretation of satellite altiometry data are difficult to verify. The GIA correction introduced in the interpretation of data from satellite altimetry depends upon the type of deglaciation model (for the last glaciation) and upon the type of crust-mantle model that is asumed. As a consequence of this (and additional factors), interpretations on modern global sea level change based on satellite altimetry vary from about 1.7 mm/yr to about 3.2 mm/yr.  

 

 

 

Global sea level since December 1992 according to the Colorado Center for Astrodynamics Research at University of Colorado at Boulder. The blue dots are the individual observations, and the purple line represents the running 121-month (ca. 10 yr) average. The two lower panels show the annual sea level change, calculated for 1 and 10 yr time windows, respectively. These values are plotted at the end of the interval considered. Data from the TOPEX/Poseidon mission have been used before 2002, and data from the Jason-1 mission (satellite launched December 2001) after 2002. Last month shown: February 2015. Last diagram update: May 24, 2015.

 

Data from tide-gauges suggest an average global sea-level rise of 1-1.5 mm/yr, while the satellite-derived record suggest a rise of more than 3 mm/yr. The rather marked difference between the two data sets has still no broadly accepted explanation, but some of the difference is likely due to administrative changes introduced into the raw data obtained by satellites. Se the paragraph below on temporal stability of the satellite-derived data.

Another factor that may explain some of the difference between tide-gauge and satellite data is probably that while any temperature-driven volumen expansion is recorded by the satellites, this change is not affecting tide-gauges at coastal locations, as the water depth here decreases towards zero. 

 

 

TEMPORAL STABILITY OF SATELLITE-DERIVED SEA-LEVEL DATA

Figure 2 from Mörner 2004, showing raw satellite altimetry data of global sea level until April 2000. Compare with the diagram below (1992-2000).

 

 

Global sea level since late 1992 according to the Colorado Center for Astrodynamics Research at University of Colorado at Boulder. The two data series show data available on July 20, 2009 (red), and the newest data available (blue). The thick lines indicate the running one year averages. The difference between the two dataseries is mainly due to a change of the zero reference level. In addition, the overall sea level increase rate until April 2009 is somewhat larger in the newest data, but not much. Compare with the diagram above (1992-2000). Last diagram update: 24 May 2015.

 

 

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