Tsonis Explains Oceans Making Climate

 

THE LITTLE BOY El Niño and natural climate change by Anastasios Tsonis is a newly published GWPF report discussing how the ocean drives climate fluctuations.  This adds to a continuing theme of this blog, Oceans Make Climate, coined by Dr. Arnd Bernaerts, also expressed as Oceans Govern Climate.  The whole PDF is worth reading.

My own effort to describe these ocean oscillations is Dynamic Duo: The Ocean-Air Partnership which discusses how several of these oscillations operate, including the ENSO (El Nino) cycle:
Other posts provide background on climate effects from oceans.

Climate Report from the Water World discusses the linkage of global temperatures to ocean temperatures (SST).

Empirical Evidence: Oceans Make Climate presents in situ measurements of the ocean-air heat exchange flux.

All essays on this theme are found in the Category: Oceans Make Climate

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Tropics Lead Ocean Warming in August

August Sea Surface Temperatures (SSTs) are now available, and we see an upward spike in ocean temps everywhere, led by sharp increases in the Tropics and SH, reversing for now the downward trajectory from the previous 12 months.  It seems likely the Tropical warming in particular factored into the active hurricane season peaking this month and next.

HadSST is generally regarded as the best of the global SST data sets, and so the temperature story here comes from that source, the latest version being HadSST3.

The chart below shows SST monthly anomalies as reported in HadSST3 starting in 2015 through August 2017.

In May despite a slight rise in the Tropics, declines in both hemispheres and globally caused SST cooling to resume after an upward bump in April.  Then in July a large drop showed in both in the Tropics and in SH, declining over 4 months.  The sharp upturn in August in the Tropics is the unusual feature this month, along with SH rising, resulting in a global average matching the previous two Augusts. Meanwhile the NH is peaking in August as in the past two years, but somewhat lower.  Despite the August warming, ENSO has gone below neutral toward La Nina, and no one expects a rise like 2015 in the coming months.

Note that higher temps in 2015 and 2016 were first of all due to a sharp rise in Tropical SST, beginning in March 2015, peaking in January 2016, and steadily declining back to its beginning level. Secondly, the Northern Hemisphere added two bumps on the shoulders of Tropical warming, with peaks in August of each year. Also, note that the global release of heat was not dramatic, due to the Southern Hemisphere offsetting the Northern one.

Note:  Last month someone asked about HadSST calculations, especially as the Global appeared to be a simple average of NH and SH, which would be misleading.  My query to Met Office received this clarifying response:

My colleague in the Climate Monitoring and Research team has advised the following:

For HadSST3, we take an area-weighted average of all the grid boxes with data in to calculate the global average. We don’t calculate the two hemispheric series and then average them. In the case of SST, this wouldn’t work because the southern hemisphere ocean area is larger than the northern hemisphere.

Kind regards,  Misha,  Weather Desk Climate Advisor

Summary

We have seen lots of claims about the temperature records for 2016 and 2015 proving dangerous man made warming.  At least one senator stated that in a confirmation hearing.  Yet HadSST3 data for the last two years show how obvious is the ocean’s governing of global average temperatures.

USS Pearl Harbor deploys Global Drifter Buoys in Pacific Ocean

The best context for understanding these two years comes from the world’s sea surface temperatures (SST), for several reasons:

  • The ocean covers 71% of the globe and drives average temperatures;
  • SSTs have a constant water content, (unlike air temperatures), so give a better reading of heat content variations;
  • A major El Nino was the dominant climate feature these years.

Solar energy accumulates massively in the ocean and is variably released during circulation events.

 

Tropics Lead Ocean Cooling

July Sea Surface Temperatures (SSTs) are now available, and we can see further ocean cooling led by plummeting temps in the  Tropics and SH, continuing the downward trajectory from the previous 12 months.

HadSST is generally regarded as the best of the global SST data sets, and so the temperature story here comes from that source, the latest version being HadSST3.

The chart below shows the last two years of SST monthly anomalies as reported in HadSST3 including July 2017.

In May despite a slight rise in the Tropics, declines in both hemispheres and globally caused SST cooling to resume after an upward bump in April.  Now in July a large drop is showing both in the Tropics and in SH, declining the last 4 months.  Meanwhile the NH is peaking in July as usual, but well down from the previous July.  The net of all this is a slightly lower Global anomaly but with likely additional future cooling led by the Tropics and also SH hitting new lows for this period.

Note that higher temps in 2015 and 2016 were first of all due to a sharp rise in Tropical SST, beginning in March 2015, peaking in January 2016, and steadily declining back to its beginning level. Secondly, the Northern Hemisphere added two bumps on the shoulders of Tropical warming, with peaks in August of each year. Also, note that the global release of heat was not dramatic, due to the Southern Hemisphere offsetting the Northern one. Note that Global anomaly for July 2017 matches closely to April 2015.  However,  SH and the Tropics are lower now and trending down compared to an upward trend in 2015.

We have seen lots of claims about the temperature records for 2016 and 2015 proving dangerous man made warming.  At least one senator stated that in a confirmation hearing.  Yet HadSST3 data for the last two years show how obvious is the ocean’s governing of global average temperatures.

USS Pearl Harbor deploys Global Drifter Buoys in Pacific Ocean

The best context for understanding these two years comes from the world’s sea surface temperatures (SST), for several reasons:

  • The ocean covers 71% of the globe and drives average temperatures;
  • SSTs have a constant water content, (unlike air temperatures), so give a better reading of heat content variations;
  • A major El Nino was the dominant climate feature these years.

Solar energy accumulates massively in the ocean and is variably released during circulation events.

 

How Trustworthy are SSTs?

Roger Andrews as promised has published his analysis of SST (Sea Surface Temperatures) datasets, based on some years of research. The essay is Making the Measurements Match the Models – Part 2: Sea Surface Temperatures and well worth a look.

Some years ago while reading to get up to speed on climate science, I was struck by a Roger Pielke Sr. comment. He said that surface temperatures are serving as a proxy for changes in heat content of the earth climate system, which is the real concern.  And air temperatures are contaminated by fluctuations in water content, such that a degree difference in the humid tropics involves much more additional heat than does the same change in extremely dry polar air.

For those who want to see the math, here it is from the Engineering Toolbox.

The enthalpy of humid air at 25C with specific moisture content x = 0.0203 kg/kg (saturation), can be calculated as 76.9 (kJ/kg). . .The same calculation for moist air at 20C gives a heat capacity of 58.2, so the 5C increase requires 18.7 kj/kg for moist air vs. 5.0 kj/kg for dry air, or a ratio of 1:3.7. Similar ratios apply at all air temperatures above 0C. Subzero air, like that in the Arctic most of the year, shows little difference in heat content between dry or saturated, since cold air doesn’t hold much water vapor. See Arctic Amplication?

One implication is that polar air temperatures lacking moisture are 2-3 times more volatile, leading to the “Arctic Amplication” effect. Even so, a thorough look into weather station records around the Arctic circle undermines fears on that account. See Arctic Warming Unalarming.

The larger point made by Pielke Sr. was that a much better proxy for global warming or cooling is provided by SSTs. Measuring temperature changes in the water itself is a much better idea, giving a more exact indication of changes in heat content. There is also the point that SSTs cover 71% of the planet surface.

Andrews knows well the difficulties in assembling SST datasets, including the bucket era and the engine intake era. He addresses directly the problematic WWII measurements, suggesting they can simply be excluded as bad data without affecting the pattern. He also compares the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) raw global SST series used to generate the global HadSST3 series, which is the most widely cited of the currently-published SST series.

There he finds that prior to 1940, there was systematic warming adjustments making HadSST temps higher than ICOADS. He attributes this to the long-standing belief that Night Marine Air Temperatures (NMATs) should synchronize with SSTs. That assumes that air moisture over the water should be fairly consistent from one location to another, and that marine air would be in thermal equilibrium with the water.

But apparently no studies have proven that assumption. I know of one empirical study of the ocean-air interface which shows considerable fluctuation in both the heat exchange and evaporation rates. See Empirical Evidence: Oceans Make Climate

The graph displays measures of heat flux in the sub-tropics during a 21-day period in November. Shortwave solar energy shown above in green labeled radiative is stored in the upper 200 meters of the ocean. The upper panel shows the rise in SST (Sea Surface Temperature) due to net incoming energy. The yellow shows latent heat cooling the ocean, (lowering SST) and transferring heat upward, driving convection. From An Investigation of Turbulent Heat Exchange in the Subtropics James B. Edson

Thanks to Roger’s work on this, we can conclude that SSTs prior to 1950 have issues, but can be encouraged that HadSST3 since then is reasonably consistent with the raw data. And in the future the ARGO record will become long enough for us to follow the trends.

USS Pearl Harbor deploys Global Drifter Buoys in Pacific Ocean

Summary

The best context for understanding global temperature effects in recent years comes from the world’s sea surface temperatures (SST), for several reasons:

  • The ocean covers 71% of the globe and drives average temperatures;
  • SSTs have a constant water content, (unlike air temperatures), so give a better reading of heat content variations;
  • Major El Ninos have been the dominant climate features these decades.

Solar energy accumulates massively in the ocean and is variably released during circulation events.

 

Ocean Cools and Air Temps Follow

June Sea Surface Temperatures (SSTs) are now available, and we can see ocean temps dropping further after a short pause and resuming the downward trajectory from the previous 12 months.

HadSST is generally regarded as the best of the global SST data sets, and so the temperature story here comes from that source, the latest version being HadSST3.

The chart below shows the last two years of SST monthly anomalies as reported in HadSST3 including June 2017.

In May despite a slight rise in the Tropics, declines in both hemispheres and globally caused SST cooling to resume after an upward bump in April.  Now in June a large spike upward in NH was overcome by an even larger drop in SH, now three months into a cooling phase. The Tropics also cooled off so the Global anomaly continued to decline.  Presently NH and SH are both changing strongly but in opposite directions.

Note that higher temps in 2015 and 2016 were first of all due to a sharp rise in Tropical SST, beginning in March 2015, peaking in January 2016, and steadily declining back to its beginning level. Secondly, the Northern Hemisphere added two bumps on the shoulders of Tropical warming, with peaks in August of each year. Also, note that the global release of heat was not dramatic, due to the Southern Hemisphere offsetting the Northern one. Note that June 2017 matches closely to June 2015, with almost the same anomalies for NH, SH and Global.  The Tropics are lower now and trending down compared to an upward trend in 2015.

June satellite measures of air over the land and oceans also shows a sharp drop.  The graph below provides UAH vs.6 TLT (lower troposphere temps) confirming the general impression from SSTs.

In contrast with SST measurements, air temps in the TLT upticked in May with all areas participating in the rise of almost 0.2C.  Then in June SH dropped 0.4C, NH down 0.2C while the Tropics declined slightly. The end result has all areas back to March values except for the Tropics.  June 2017 compares closely with July 2015 but with no signs of an impending El Nino.

We have seen lots of claims about the temperature records for 2016 and 2015 proving dangerous man made warming.  At least one senator stated that in a confirmation hearing.  Yet HadSST3 data for the last two years show how obvious is the ocean’s governing of global average temperatures.

USS Pearl Harbor deploys Global Drifter Buoys in Pacific Ocean

The best context for understanding these two years comes from the world’s sea surface temperatures (SST), for several reasons:

  • The ocean covers 71% of the globe and drives average temperatures;
  • SSTs have a constant water content, (unlike air temperatures), so give a better reading of heat content variations;
  • A major El Nino was the dominant climate feature these years.

Solar energy accumulates massively in the ocean and is variably released during circulation events.

 

Ocean Cooling Resumes

May Sea Surface Temperatures (SSTs) are now available, and we can see ocean cooling resuming after a short pause from the downward trajectory during the previous 12 months.

HadSST is generally regarded as the best of the global SST data sets, and so the temperature story here comes from that source, the latest version being HadSST3.

The chart below shows the last two years of SST monthly anomalies as reported in HadSST3 including May 2017.

 

After an upward bump in April 2017 due to the Tropics and NH, the May SSTs show the average declining slightly.  Note the Tropics recorded a rise, but not enough to offset declines in both hemispheres and globally.  SH is now two months into a cooling phase. The present readings compare closely with April 2015, but currently with no indication of an El Nino event any time soon.

Note that higher temps in 2015 and 2016 were first of all due to a sharp rise in Tropical SST, beginning in March 2015, peaking in January 2016, and steadily declining back to its beginning level. Secondly, the Northern Hemisphere added two bumps on the shoulders of Tropical warming, with peaks in August of each year. Also, note that the global release of heat was not dramatic, due to the Southern Hemisphere offsetting the Northern one.

Satellite measures of the air over the oceans give a slightly different result.  The graph below provides UAH vs.6 TLT (lower troposphere temps) over the oceans confirming the general impression from SSTs.

In contrast with SST measurements, air temps in the TLT over the oceans upticked in May with all areas participating in the rise of almost 0.2C.  In the satellite dataset, it is quite noticeable that land air temps rose quite strongly and may have caused air temps in the May TLT over oceans to show higher anomalies than the SSTs.

We have seen lots of claims about the temperature records for 2016 and 2015 proving dangerous man made warming.  At least one senator stated that in a confirmation hearing.  Yet HadSST3 data for the last two years show how obvious is the ocean’s governing of global average temperatures.

USS Pearl Harbor deploys Global Drifter Buoys in Pacific Ocean

The best context for understanding these two years comes from the world’s sea surface temperatures (SST), for several reasons:

  • The ocean covers 71% of the globe and drives average temperatures;
  • SSTs have a constant water content, (unlike air temperatures), so give a better reading of heat content variations;
  • A major El Nino was the dominant climate feature these years.

Solar energy accumulates massively in the ocean and is variably released during circulation events.

 

April Pause in Ocean Cooling

 

Ocean temperature measurements come from a global array of 3,500 Argo floats and other ocean sensors. Credits: Argo Program, Germany/Ifremer

April Sea Surface Temperatures are now available, and we can see a pause in the downward trajectory over the previous 13 months.

HadSST is generally regarded as the best of the global SST data sets, and so the temperature story here comes from that source, the latest version being HadSST3.

The chart below shows the last two years of SST monthly anomalies as reported in HadSST3 including April 2017.

In April 2017, the SH appears to be entering its cooler phase, while both the tropics and NH ticked upward from March, causing the Global anomaly to rise for the fourth month in a row.  The downward momentum has stopped, except now the SH (mostly ocean) has started down from a lower peak than a year ago.  It was the SH that was pulling up the Global average the previous three months.   The Tropics and NH may or may not start a new warming cycle, depending upon the appearance of El Nino.

Note that higher temps in 2015 and 2016 were first of all due to a sharp rise in Tropical SST, beginning in March 2015, peaking in January 2016, and steadily declining back to its beginning level. Secondly, the Northern Hemisphere added two bumps on the shoulders of Tropical warming, with peaks in August of each year. Also, note that the global release of heat was not dramatic, due to the Southern Hemisphere offsetting the Northern one.

Satellite measures of the air over the oceans give a similar result.  The graph below provides UAH vs.6 TLT (lower troposphere temps) over the oceans confirming the impression from SSTs.

Once again it is the Tropical and NH oceans that drove the warming that peaked a year ago.  SH  moderated the Global averages, though the air temps over the oceans are more synchronized than is the case with SSTs. Note how in April all anomalies converged on 0.3C.

We have seen lots of claims about the temperature records for 2016 and 2015 proving dangerous man made warming.  At least one senator stated that in a confirmation hearing.  Yet HadSST3 data for the last two years show how obvious is the ocean’s governing of global average temperatures.

The best context for understanding these two years comes from the world’s sea surface temperatures (SST), for several reasons:

  • The ocean covers 71% of the globe and drives average temperatures;
  • SSTs have a constant water content, (unlike air temperatures), so give a better reading of heat content variations;
  • A major El Nino was the dominant climate feature these years.

Solar energy accumulates massively in the ocean and is variably released during circulation events.

 

Barents Icicles 2017

A chart of Barents Ice Cycles looks a lot like the icicles above, except upside down since Barents Sea is usually all water by September. Notice the black lines in the graph below hitting bottom near zero.

Note also the anomalies in red are flat until 1998, then decline to 2007 and then flat again.

Why Barents Sea Ice Matters

Barents Sea is located at the gateway between the Arctic and North Atlantic. Previous posts (here and here) have discussed research suggesting that changes in Barents Sea Ice may signal changes in Arctic Sea Ice a few years later. As well, the studies point to changes in heat transport from the North Atlantic driving the Barents Sea Ice, along with changes in salinity of the upper layer. And, as suggested by Zakharov (here), there are associated changes in atmospheric circulations, such as the NAO (North Atlantic Oscillation).

Here we look at MASIE over the last decade and other datasets over longer terms in search for such patterns.

Observed Barents Sea Ice

Below is a more detailed look at 2017 compared with recent years.

This graph shows over the last 11 years, on average Barents sea ice starts declining beginning with April and melts out almost completely in September before recovering.  Some years, like 2014, the decline started much later and stopped with 100k km2 of ice persisting, resulting in the highest annual extent in the last decade.   Last year, 2016, was the opposite anomaly with much less ice than average all year.  2007 had the least Arctic ice overall in the last decade and was close to average in Barents during the summer months.

Note how exceptional is 2017 Barents ice extent.  It began extremely low in January and grew sharply to reach average by February, then dipped in March before rising strongly again in April.  It remains to be seen how much ice will grow, how late and how much will melt this year.

 

North Atlantic Meteorology in 2017

From AER comes more evidence of cooling in the North Atlantic and favorable conditions for ice formation there.

Dr. Judah Cohen provides his latest Arctic Oscillation and Polar Vortex Analysis and Forecast
on April 21, 2017.

  • Currently pressure/geopotential height anomalies are mostly positive on the North Pacific side of the Arctic but mostly negative across the North Atlantic side of the Arctic with mostly negative pressure/geopotential height anomalies across the mid-latitude ocean basins. This is resulting in a negative Arctic Oscillation (AO) but a positive North Atlantic Oscillation (NAO).
  • Despite the positive NAO, temperatures are below normal across western Eurasia including much of Europe as a strong block/high pressure has developed in the eastern North Atlantic with a cold, northerly flow downstream of the block across Europe.
  • The blocking high in the eastern North Atlantic is predicted to drift northward contributing to a negative bias to the AO and eventually the NAO over the next two weeks. Therefore, the pattern of cool temperatures across western Eurasia including Europe looks to continue into the foreseeable future.

Background on Barents from the Previous Post

Annual average BSIE (Barents Sea Ice Extent) is 315k km2, varying between 250k and 400k over the last ten years. The volatility is impressive, considering the daily Maximums and Minimums in the record. Average Max is 781k, ranging from 608k to 936k. Max occurs on day 77 (average) with a range from day 36 to 103. Average Min is 11k on day 244, ranging from 0k to 77k, and from days 210 to 278.

In fact, over this decade, there are not many average years. Five times BSIE melted to zero, two were about average, and 3 years much higher: 2006-7 were 2 and 3 times average, and 2014 was 7 times higher at 77k.

As for Maxes, only 1 year matched the 781k average. Four low years peaked at about 740k (2006,07,08 and 14), and the lowest year at 608k (2012). The four higher years start with the highest one, 936k in 2010, and include 2011, 13, and 15.

Comparing Barents Ice and NAO
Barents Masierev

This graph confirms that Barents winter extents (JFMA) correlate strongly (0.73) with annual Barents extents. And there is a slightly less strong inverse correlation with NAO index (-0.64). That means winter NAO in its negative phase is associated with larger ice extents, and vice-versa.

Comparing Barents Ice and Arctic Annual

Barents and Arctic

Arctic Annual extents correlate with Barents Annuals at a moderately strong 0.46, but have only weaker associations with winter NAO or Barents winter averages. It appears that 2012 and 2015 interrupted a pattern of slowly rising extents.

NAO and Arctic Ice Longer Term

Fortunately there are sources providing an history of Arctic ice longer term and overlapping with the satellite era. For example:

Observed sea ice extent in the Russian Arctic, 1933–2006 Andrew R. Mahoney et al (2008)
http://seaice.alaska.edu/gi/publications/mahoney/Mahoney_2008_JGR_20thC_RSI.pdf

Russian Arctic Sea Ice to 2006

Mahoney et al say this about Arctic Ice oscillations:

We can therefore broadly divide the ice chart record into three periods. Period A, extending from the beginning of the record until the mid-1950s, was a period of declining summer sea ice extent over the whole Russian Arctic, though not consistently in every individual sea. . . Period B extended from the mid-1950s to the mid- 1980s and was a period of generally increasing or stable summer sea ice extent. For the Russian Arctic as a whole, this constituted a partial recovery of the sea ice lost during period A, though this is not the case in all seas. . . Period C began in the mid-1980s and continued to the end of the record (2006). It is characterized by a decrease in total and MY sea ice extent in all seas and seasons.

Comparing Arctic Ice with winter NAO index

The standardized seasonal mean NAO index during cold season (blue line) is constructed by averaging the monthly NAO index for January, February and March for each year. The black line denotes the standardized five-year running mean of the index. Both curves are standardized using 1950-2000 base period statistics.

The graph shows roughly a 60 year cycle, with a negative phase 1950-1980 and positive 1980 to 2010. As described above, Arctic ice extent grew up to 1979, the year satellite ice sensing started, and declined until 2007. The surprising NAO uptick recently coincides with the anomalous 2012 and 2015 meltings.

As of January 2016 NAO went negative for the first time in months.  There appears to be some technical difficulties with more recent readings.

Summary

If the Barents ice cycle repeats itself over the next decades, we should expect Arctic ice extents to grow as part of a natural oscillation. The NAO atmospheric circulation pattern is part of an ocean-ice-atmosphere system which is driven primarily by winter changes in the North Atlantic upper water layer.

Self-Oscillating Sea Ice System

Self-Oscillating Sea Ice System  See here.

 

Mann-made Global Cooling

The usual suspects are sounding alarms about the ocean “conveyor belt” AMOC slowing down, and predicting that global warming will result in global cooling.

The Ocean’s Conveyor Belt Is Slowing Down: What You Need to Know About AMOC, Greenland and ‘Unprecedented’ Sea Level Rise

Using data gathered from ice cores, tree rings and coral samples, the research team (led by the Potsdam Institute for Climate Impact Research in Germany) posits that weakness in the AMOC after 1975 “is an unprecedented event in the past millennium.”

Planet Expert Michael Mann co-authored the study and told ClimateCentral that a “full-on collapse” of the AMOC could be possible in the coming decades.

The exact consequences will be difficult to predict, but it will definitely have an impact on marine life, which benefits from the nutrients the AMOC delivers up from the ocean depths. “The most productive region, in terms of availability of nutrients, is the high latitudes of the North Atlantic,” said Mann. “If we lose that, that’s a fundamental threat to our ability to continue to fish.”

Hurricanes and nor’easters like the recent Winter Storm Juno that brought Snowmageddon to the East Coast could also become more common, he warned.

“If you shut down this mode of ocean circulation, you’re denying the climate system one of its modes of heat transport,” said Mann. “if you deny it one mode of transport, it’s often the case that you will see other modes of transport increase.”

The published paper is Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation by Stefan Rahmstorf, Jason E. Box, Georg Feulner, Michael E. Mann, Alexander Robinson, Scott Rutherford & Erik J. Schaffernicht 23 March 2015 (Three of the first four names are the most outspoken climatists of our time.)  The Abstract is not as alarming as Mann’s interview.

Possible changes in Atlantic meridional overturning circulation (AMOC) provide a key source of uncertainty regarding future climate change. Maps of temperature trends over the twentieth century show a conspicuous region of cooling in the northern Atlantic. Here we present multiple lines of evidence suggesting that this cooling may be due to a reduction in the AMOC over the twentieth century and particularly after 1970. Since 1990 the AMOC seems to have partly recovered. This time evolution is consistently suggested by an AMOC index based on sea surface temperatures, by the hemispheric temperature difference, by coral-based proxies and by oceanic measurements. We discuss a possible contribution of the melting of the Greenland Ice Sheet to the slowdown. Using a multi-proxy temperature reconstruction for the AMOC index suggests that the AMOC weakness after 1975 is an unprecedented event in the past millennium (p > 0.99). Further melting of Greenland in the coming decades could contribute to further weakening of the AMOC. (wiggle words in bold)

Recent Observations of AMOC Trends

Activists pushing global warming/climate change are trying to get ahead of the likely coming cooling phase following the recent warming phase of the natural climate cycle. The kernal of truth in their hand waving resides in the initial report from the RAPID project.

The RAPID moorings being deployed. Credit: National Oceanography Centre

The RAPID project report is Observed decline of the Atlantic meridional overturning circulation 2004–2012 by D. A. Smeed, G. D. McCarthy et al.

10-year time series of the strength of AMOC, measured as water transported in Sverdrups (millions of cubic metres of water per second). Graph shows 10-day average measurements (grey line) and 180-day average (red line). Source: Srokosz & Bryden ( 2015)

“We have shown that there was a slowdown in the AMOC transport between 2004 and 2012 amounting to an average of −0.54 Sv yr−1 (95 % c.i. −0.08 to −0.99 Sv yr−1) at 26◦ N, and that this was primarily due to a strengthening of the southward flow in the upper 1100 m and a reduction of the southward transport of NADW below 3000 m. This trend is an order of magnitude larger than that predicted by climate models associated with global climate change scenarios, suggesting that this decrease represents decadal variability in the AMOC system rather than a response to climate change. (lower North Atlantic deep water (LNADW) upper (UNADW) . . .our observations show no significant change in the Gulf Stream transport over the 2004–2012 period when the AMOC is decreasing.”

AMOC Observations in Historical Context

Oceanographers are not alarmed, unlike activists Ramsdorf, Mann and Box.  For example these recent papers: Recent slowing of Atlantic overturning circulation as a recovery from earlier strengthening by Laura C. Jackson, K. Andrew Peterson, Chris D. Roberts & Richard A. Wood 23 May 2016.   Abstract:

The Atlantic meridional overturning circulation (AMOC) has weakened substantially over the past decade. Some weakening may already have occurred over the past century, and global climate models project further weakening in response to anthropogenic climate change. Such a weakening could have significant impacts on the surface climate.

However, ocean model simulations based on historical conditions have often found an increase in overturning up to the mid-1990s, followed by a decrease. It is therefore not clear whether the observed weakening over the past decade is part of decadal variability or a persistent weakening. Here we examine a state-of-the-art global-ocean reanalysis product, GloSea5, which covers the years 1989 to 2015 and closely matches observations of the AMOC at 26.5° N, capturing the interannual variability and decadal trend with unprecedented accuracy.

The reanalysis data place the ten years of observations—April 2004 to February 2014—into a longer-term context and suggest that the observed decrease in the overturning circulation is consistent with a recovery following a previous increase. We find that density anomalies that propagate southwards from the Labrador Sea are the most likely cause of these variations. We conclude that decadal variability probably played a key role in the decline of the AMOC observed over the past decade. (my bolds)

And this paper: A reversal of climatic trends in the North Atlantic since 2005
by Jon Robson, Pablo Ortega & Rowan Sutton 06 June 2016. Abstract:

In the mid-1990s the North Atlantic subpolar gyre warmed rapidly, which had important climate impacts such as increased hurricane numbers and changes to rainfall over Africa, Europe and North America. Evidence suggests that the warming was largely due to a strengthening of the ocean circulation, particularly the Atlantic Meridional Overturning Circulation. Since the mid-1990s direct and indirect measurements have suggested a decline in the strength of the ocean circulation, which is expected to lead to a reduction in northward heat transport.

Here we show that since 2005 a large volume of the upper North Atlantic Ocean has cooled significantly by approximately 0.45 °C or 1.5 × 1022 J, reversing the previous warming trend. By analysing observations and a state-of-the-art climate model, we show that this cooling is consistent with a reduction in the strength of the ocean circulation and heat transport, linked to record low densities in the deep Labrador Sea. The low density in the deep Labrador Sea is primarily due to deep ocean warming since 1995, but a long-term freshening also played a role. The observed upper ocean cooling since 2005 is not consistent with the hypothesis that anthropogenic aerosols directly drive Atlantic temperatures.

Summary

Once again climatists exaggerate and ignore ocean oscillations in favor of their CO2 hysteria.  In the details of the AMOC report are observations that the heat transports slowed in part, increased in another part, and the warm gulf stream flow remained the same.

The AMO index supports this latter point, showing the continuing pulses of warm Atlantic water into the Arctic.

The next phase of the AMO will be cooler than the present, and will not be caused by human activity.

Background on AMOC is at Climate Pacemaker: The AMOC

Ocean Physics in a Cup of Coffee

 

The Great Arctic Cyclone of 2012 from satellite.

 Recently I posted Ocean Climate Ripples summarizing an article by Dr. Arnd Bernaerts on how humans impact upon the oceans and thereby the climate. His references to activities in the North and Baltic Seas included this comment:

It works like a spoon stirring hot coffee, attracting cold air from Siberia. In this respect they serve as confined research regions, like a unique field laboratory experiment.

This post presents an article by John S. Wettlaufer who sees not only the oceans but cosmic patterns in coffee cup vorticies. His essay is The universe in a cup of coffee.  (Bolded text is my emphasis.)

John Wettlaufer is the A. M. Bateman Professor of Geophysics, Physics, and Applied Mathematics at Yale University in New Haven, Connecticut.


As people throughout the world awake, millions of them every minute perform the apparently banal act of pouring cold milk into hot coffee or tea. Those too groggy to reach for a spoon might notice upwelling billows of milk separated by small, sinking, linear dark features such as shown in panel a of the figure. The phenomenon is such a common part of our lives that even scientists—trained to be observant—may overlook its importance and generality. The pattern bears resemblance to satellite images of ocean color, and the physics behind it is responsible for the granulated structure of the Sun and other cosmic objects less amenable to scrutiny.

(a) Everyone knows that if you wait for a while coffee will get cold. The primary agent doing the cooling is evaporatively driven convection. Pour cold milk into hot coffee and wait. The cold milk mixes very little as it sinks to the bottom of the cup, but eventually cold plumes created by evaporation at the surface sink down and displace the milk. In time, a pattern forms of upwelling (lighter) and downwelling (darker) fluid.

Archimedes pondered the powerful agent of motion known as buoyancy more than two millennia ago. Children do, too, when they imagine the origins of cloud animals on a summer’s day. The scientific study of thermal and compositional buoyancy originated in 1798 with a report by Count Rumford intended to disabuse believers of the caloric theory. Nowadays, buoyancy is at the heart of some of the most challenging problems in nonlinear physics—problems that are increasingly compelling. Answers to fundamental questions being investigated today will have implications for understanding Earth’s heat budget, the transport of atmospheric and oceanographic energy, and, as a corollary, the climate and fate of stars and the origins of planets. Few avenues of study combine such basic challenges with such a broad swath of implications. Nonetheless, the richness of fluid flow is rarely found in undergraduate physics courses. 

Wake up and smell the physics

The modern theory of hydrodynamic stability arose from experiments by Henri Bénard, who heated, from below, a thin horizontal layer of spermaceti, a viscous, fluid wax. For small vertical temperature gradients, Bénard observed nothing remarkable; the fluid conducted heat up through its surface but exhibited no wholesale motion as it did so. However, when the gradient reached a critical value, a hexagonal pattern abruptly appeared as organized convective motions emerged from what had been an homogenous fluid. The threshold temperature gradient was described by Lord Rayleigh as reflecting the balance between thermal buoyancy and viscous stresses, embodied in a dimensionless parameter now called the Rayleigh number. 

When the momentary thermal buoyancy of a blob of fluid—provided by the hot lower boundary—overcomes the viscous stresses of the surrounding fluid, wholesale organized motion ensues. The strikingly structured fluid, with its up-and-down flow assuming specific geometries, is an iconic manifestation of how a dissipative system can demonstrate symmetry breaking (the up-and-down flow distinguishes horizontal positions even though the lower boundary is at a uniform temperature), self-organization, and beauty. (See the article by Leo Kadanoff in PHYSICS TODAY, August 2001, page 34.)

Astrophysicists and geophysicists can hardly make traction on many of the problems they face unless they come to grips with convection—and their quests are substantially complicated by their systems’ rotations. Despite the 1835 publication of Gaspard-Gustave Coriolis’s Mémoire sur les équations du mouvement relatif des systèmes de corps (On the Equations of Relative Motion of a System of Bodies), debate on the underlying mechanism behind the deflection of the Foucault pendulum raged in the 1905 volume of Annalen der Physik, the same volume in which Albert Einstein introduced the world to special relativity. Maybe the lack of comprehension is not so surprising: Undergraduates still more easily grasp Einstein’s theory than the Coriolis effect, which is essential for understanding why, viewed from above, atmospheric circulation around a low pressure system over a US city is counterclockwise but circulation over an Australian city is clockwise. 

Practitioners of rotating-fluid mechanics generally credit mathematical physicist Vagn Walfrid Ekman for putting things in the modern framework, in another key paper from 1905. Several years earlier, during his famous Fram expedition, explorer Fridtjof Nansen had observed that ice floes moved to the right of the wind that imparted momentum to them. Nansen then suggested to Ekman that he investigate the matter theoretically. That the deflection was due to the ocean’s rotating with Earth was obvious, but Ekman described the corrections that must be implemented in a noninertial reference frame. Since so much in the extraterrestrial realm is spinning, scientists taken by cosmological objects eventually embraced Ekman’s formulation and sought evidence for large-scale vortex structures in the accretion disks around stars. Vortices don’t require convection and when convection is part of a vortex-producing system, additional and unexpected patterns ensue. 

Cream, sugar, and spinning

The Arctic Ocean freezes, cooling and driving salt into the surface layers. Earth’s inner core solidifies, leaving a buoyant, iron-depleted metal. Rapidly rising air from heated land surfaces creates thunderstorms. Planetary accretion disks receive radiation from their central stars. In all these systems, rotation has a hand in the fate of rising or sinking fluid. What about your steaming cup of coffee: What happens when you spin that?

(b) Several views of a volume of water 11.4 cm deep with a cross section of 22.9 × 22.9 cm. Panel b shows the liquid about 7.5 minutes after the fluid is set in motion at a few tenths of a radian per second. The principal image indicates particle density (light is denser) at a depth of 0.6 cm below the surface. The inset is a thermal image of the surface

Place the cup in the center of a spinning record player— some readers may even remember listening to music on one of those. The friction from the wall of the cup transmits stresses into the fluid interior. If the coffee is maintained at a fixed temperature for about a minute, every parcel of fluid will move at the same angular velocity; the coffee is said to be spun up.

On the time scales of contemporary atmospheric and oceanographic phenomena, Earth’s rotation is indeed a constant, whereas the time variation of the rotation could be important for phenomena in planetary interiors, the evolution of an accretion disk, or tidal perturbations of a distant moon. Thus convective vortices are contemplated relative to a rotating background flow. Perturbations in the rotation rate revive the role of boundary friction and substantially influence the interior circulation. Moreover, evaporation and freezing represent additional perturbations, which alter how the fluid behaves as stresses attempt to enforce uniform rotation. Returning to the coffee mug as laboratory, the model system shown in panel b of the figure reveals how the added complexity of rotation momentarily organizes the pattern seen in panel a into concentric rings of cold and warm fluid.

(c) Panel c shows the breakup of the rings, 11 minutes after the initiation of rotation, due to a shearing instability.

Fundamental competitions play out when you rotate your evaporating coffee. As we have seen, evaporative cooling drives narrow regions of downward convection; significant viscous and Coriolis effects balance each other in those downwelling regions. Rotation then dramatically organizes the sinking cold sheets and rising warm billows into concentric rings that first form at the center of the cup. By about 7.5 minutes after rotation has been initiated, the rings shown in panel b have grown to cover most of the horizontal plane. Their uniform azimuthal motion exists for about 3.5 minutes, at which time so-called Kelvin–Helmholtz billows associated with the shearing between the rings appear at their boundaries, grow, and roll up into vortices; see panel c. Three minutes later, as shown in panel d, those vortices lose their azimuthal symmetry and assemble into a regular vortex grid whose centers contain sinking fluid.

(d) As panel d shows, at 14 minutes the breakup leads to a grid of vortices. (Adapted from J.-Q. Zhong, M. D. Patterson, J. S. Wettlaufer, Phys. Rev. Lett. 105, 044504, 2010.)

Panel d shows one type of coherent structure that forms in rotating fluids and other mathematically analogous systems if the persistence time of the structure—vortices here— is much longer than the rotational period. Other well-known examples are Jupiter’s Great Red Spot, which is an enduring feature of the chaotic Jovian atmosphere, and the meandering jet streams on Earth.

Moreover, persistent vortices in superconductors and superfluids organize themselves. Indeed, it appears that vortices in superconductors are as mobile as their counterparts in inviscid fluids. And although scientists have long studied rotating convective superfluids, the classical systems considered in this Quick Study suggest that we may yet find surprising analogies in superconductors. Will we one day see superconducting jet streams?

If you are reading this article with a cup of coffee, put it down and take a closer look at what is going on in your cup.

Summary

Wettlaufer has been an advocate for getting the physics right in climate models.  His analogy of a cuppa coffee is actually a demonstration of mesoscale fluid and rotational dynamics and perturbations that still defy human attempts to simulate climate operations.