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North Atlantic Ocean Cooling Rapidly

Kenneth Richard, NoTricksZone

While it has understandably not received much, if any, media attention, the North Atlantic Ocean has been rapidly cooling since the mid-2000s, or for more than 10 years now.

The longer the cooling trend continues — and scientists are projecting more cooling for the coming decades  —  the more difficult it will be to ignore.   The North Atlantic Ocean is, after all, a key trend-setter for hemispheric- and perhaps even global-scale climate changes.

In their new paper, for example, Reynolds and colleagues (2017) point out that natural fluctuations in heat transport initiated by the Atlantic Meridional Overturning Circulation (AMOC) are “directly linked” to precipitation and warming/cooling temperature trends in Africa, Brazil, North America, and Europe.   Not only that, but the authors explain that a centennial-scale reduction in surface heat transport (AMOC) can explain the dramatic reduction in surface temperatures from the warmth of the Medieval Warm Period to the frigid Little Ice Age, which, of course, could imply that centennial-scale increases in surface heat transport could explain warming periods.

Reynolds et al., 2017       Evidence derived from instrumental observations suggest that Atlantic variability, associated with changes in SSTs and fluctuations in the strength of the Atlantic Meridional Overturning Circulation (AMOC), is directly linked with broader scale climate variability, including Brazilian and Sahel precipitation (Folland et al., 1986 and Folland et al., 2001), Atlantic hurricanes and storm tracks (Goldenberg et al., 2001 and Emanuel, 2005), and North American and European temperatures (Sutton and Hodson, 2005, Knight et al., 2006 and Mann et al., 2009). Furthermore, evidence derived from palaeoceanographic records suggests that a reduction in the meridional heat transport through the surface components of the AMOC was in part responsible for the reductions in temperatures associated with the Medieval Climate Anomaly (MCA; 1000–1450) to Little Ice Age (LIA; 1450–1850) transition (Lund et al., 2006, Trouet et al., 2009, Trouet et al., 2012, Wanamaker et al., 2012 and Moffa-Sánchez et al., 2014).

Examining the Reynolds et al. (2017) graph of North Atlantic sea surface temperatures since the early 1800s, we notice that temperatures (shown to have declined by about -0.45 °C since 2005) are colder now than they were in the 1940s and 1950s, and that even the early 1800s had warmer temperatures than now.

Serykh (2016) points out that the warming enjoyed across Europe and Asia between the 1970s and late 1990s may have been associated with natural decadal-scale oscillations in heat transport.   Similar to Reynolds et al. (2017), Serykh’s graph of ocean heat content reveals no net warming in the last 60 years.

Serykh, 2016       A dipole structure of inter-decadal variations in the heat content of the ocean and heat fluxes from the ocean to the atmosphere has been detected in the North Atlantic. The following fact deserves special attention: the cyclonic and anti-cyclonic atmospheric circulation anomalies, as well as the decrease and increase in the ocean heat content, take place concurrently and quasi-synchronously in the Iceland minimum and Azores maximum regions. Owing to this, the western heat transport anomalies along the 50th parallel increase or decrease the transport of heat from the Atlantic Ocean to the Euro-Asian continent, and the climate in Europe and Siberia becomes more marine or more continental. The very fast climate warming of the Euro-Asian continent that began in the 1970s may be associated with the enhanced heat transport from the North Atlantic in this period. This is evident from the fields and time series obtained in the present paper. The hiatus of this warming after 1999 may be due to the decreased heat transfer from the North Atlantic Ocean to the Eurasian territory.

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