Michael Mann: Global Warming Speed Bump? The Answer May Be Blowing in the Wind!

by Michael E. Mann, Huffington Post, February 10, 2014

An interesting new paper by Matthew England and colleagues just published in the journal Nature Climate Change tosses another hat in the ring when it comes to the so-called "hiatus" or "pause" (I prefer "speed bump") in global warming.

As I have discussed previously, the fact that global surface temperatures have not increased as much over the past decade as many climate models predict they should have, doesn't necessarily contradict the model predictions at all. In reality, the speed bump may simply reflect the short-term natural fluctuations of climate (and keep in mind that, by some measures such as the melting of Arctic sea ice, climate change is actually proceeding faster than the models have predicted):

Yet there are numerous explanations of the slowing of warming (unaccounted for effects of volcanic eruptions and natural variability in the amount of heat buried in the ocean) that do not imply a lower sensitivity of the climate to greenhouse gases.

The new paper by England et al. is relevant to the latter of the two potential explanations provided above, namely how much heat is being buried below the ocean surface.

The explanation for the speed bump, the authors say, might lie in the stronger-than-normal winds in the tropical Pacific for much of the past decade. The equatorial trade winds are responsible for the upwelling of cold deep water in the eastern equatorial Pacific (why the Galapagos Islands are a cold place to go swimming, despite being located near the equator). That cold water spreads out over a large part of the eastern and central tropical Pacific. Make those winds stronger, and you get cooler surface temperatures over a large region of Earth's tropics, and modestly lower global surface temperatures of 0.1-0.2 C (enough to explain much if not all of the slowing of global warming over this short time frame). The surface cooling is associated, in turn, with greater burial of heat beneath the ocean surface.

Such conditions are basically equivalent to the flip-side of El Niño, known as La Niña. In other words, the slowing of global warming may relate, at least in part, to the tendency for more frequent La Niña-like conditions in recent years. That gives us stronger trade winds in the eastern tropical Pacific, more burial of heat below the ocean surface, colder tropical Pacific sea surface temperatures, and slightly cooler global average temperatures than we might otherwise have seen.

The $64,000 question, then, is whether this increased tendency for La Niña-like conditions over the past decade is entirely natural in origin, or whether it might instead in some way be tied to climate change itself. If we are simply witnessing a temporary natural excursion that is part of an internal oscillation in the climate system, then things might easily turn around in the years ahead. Just as we are getting lulled into a sort of false complacency about the rate of global warming, we may be caught by surprise as the natural oscillation swings in the other direction, and the globe warms even faster than the models predict it should.

On the other hand, if we are instead seeing a subtle effect of global warming in which increased greenhouse gas concentrations are, seemingly paradoxically, favoring the colder  state of the climate system, then future global warming might end up being just a bit less than many of the current climate models are predicting. Keep in mind that the effect in question only amounts to at most one or two tenths of a degree C, and business-as-usual fossil fuel emissions are likely to warm the globe by 4-5 C (7-9 F) by the end of the century. So we're talking about a very minor correction. But nonetheless, it would potentially constitute a small additional negative feedback in the climate system, and a slight mitigation of future warming in comparison with prevailing climate models currently project.

As it happens, I have been arguing for this possibility for some time now, a somewhat inconvenient fact for those who would prefer to label me a "climate change alarmist." ;-)

In the section "It's the Anomalies, Stupid" of Chapter 6 ("A Candle in the Dark") of my book The Hockey Stick and the Climate Wars, I discuss work I published more than a decade ago that provides some possible evidence for a mechanism known as the tropical Pacific ocean thermostat whereby global warming, counter-intuitively, leads to a greater prevalence for La Niña-like conditions.

As I describe in the book, it all relates to controversial research by another climate scientist that dates back nearly 30 years:

In the mid-1980s, a scientist named Paul Handler from the University of Illinois had suggested a relationship between explosive tropical volcanic eruptions and the timing of major El Niño events, but his findings were based on only a short interval of time: the instrumental record available back through the late nineteenth century.

Other properly skeptical scientists argued that the statistical relationship was not very robust -- remove one major volcanic eruption, for example, and the relationship is no longer statistically significant -- and there was no convincing physical explanation given for why this relationship between volcanic eruptions and El Niño events should exist in the first place.

My colleagues and I used the paleoclimate reconstructions that we had published in the late 1990s to further test this hypothesis:

With the longer-term record of El Niño events that we now had from our proxy temperature reconstructions (we could reliably reconstruct the history of El Niño back through the early seventeenth century), we could see whether the relationship held up over a time period that was both longer than, and completely independent of, the modern period Handler had analyzed. What's more, Amy Clement and Mark Cane of Columbia's Lamont Doherty Earth Observatory had provided an important link in establishing a plausible physical mechanism for the purported relationship. In a provocative 1997 article, they used the so-called Cane-Zebiak model of the El Niño phenomenon to demonstrate that the very same mechanisms responsible for El Niño held some counterintuitive implications for how the tropical Pacific Ocean and atmosphere system might respond to an external heating. The mechanism they identified, known as the "tropical Pacific Ocean thermostat," implied that the eastern and central tropical Pacific might actually cool down! The pattern of cooling resembled the opposite of El Niño -- La Niña -- and it resulted from subtle ways that wind patterns and ocean currents influence each other in the equatorial Pacific. Clement, Cane, and collaborators argued that this mechanism could paradoxically cause the climate to look more like the cold La Niña state even as global warming proceeds.

As I go on to explain:

If the thermostat mechanism caused the climate to look more like La Niña in response to heating (by either increased greenhouse gas concentrations or an upturn in solar output), it ought -- my colleagues and I reasoned -- to exhibit an El Niño-like pattern in response to the cooling influence of an explosive volcanic eruption. Not any old volcanic eruption would do; the volcanic aerosols would have to block out sunlight from reaching the surface of the tropical Pacific Ocean, something that -- because of large-scale wind patterns -- only a tropical eruption will do. It made perfect sense to us, now, why Handler had seen a clear relationship only with tropical volcanic eruptions. We confirmed Handler's original findings in our own independent analysis of the relationships between volcanic activity and El Niño over the past several centuries.

Some of our more recent work appears to provide further support for the mechanism from the paleoclimate record (see this more detailed discussion from a few years ago at the climate blog RealClimate I contribute to):

We showed in recent work, for example, that the same mechanisms described above may help to explain many of the now-better-established features of the medieval climate anomaly. For example, the La Niña-like temperature pattern in the tropical Pacific we have discerned for the MCA [Medieval Climate Anomaly] when solar output was high and volcanic eruptions were few, seems to be consistent with the tropical Pacific thermostat mechanism.

Finally, this matter illustrates how scientific uncertainty is not necessarily our friend when it comes to projected climate change impacts, and it provides a good example of true healthy scientific skepticism (as opposed to the sort of denialism/contrarianism that is too often passed off as 'skepticism'):

The implications of this seemingly innocuous finding are not trivial. It suggests the possibility that heating by increased greenhouse gas concentrations could lead to a more La Niña-like state of the climate, associated, for example, with intensified drought in the desert Southwest and increased Atlantic hurricane activity. If the minority of climate models that produce that response are correct, we might see a greater exacerbation of these effects than the IPCC currently projects.

We have then a genuine area of uncertainty in the science with significant potential societal implications, one where a healthy dose of skepticism is warranted in interpreting the predictions of state-of-the-art models. Climate scientists continue to seek more data and make further refinements in the models as they strive to resolve this issue. Here we are very much in the midst of science's erratic path forward.

The latest study by England et al. reflects the latest excursion of this erratic path. Stay tuned!

Michael Mann is Distinguished Professor of Meteorology at Pennsylvania State University and author of "The Hockey Stick and the Climate Wars: Dispatches from the Front Lines" (now available in paperback with a new guest foreword by Bill Nye "The Science Guy")

Follow Michael E. Mann on Twitter: www.twitter.com/MichaelEMann

http://www.huffingtonpost.com/michael-e-mann/global-warming-speed-bump_b_4756711.html

Deep Atlantic Circulation During the Last Glacial Maximum and Deglaciation

How has deep ocean circulation changed in the past, and how have the changes affected Earth's climate? Reconstructing ocean circulation and climate history using geological records.

Delia W. Oppo (Department of Geology and Geophysics, Woods Hole Oceanographic Institution) and William B. Curry (Department of Geology and Geophysics, Woods Hole Oceanographic Institution)

Citation: Oppo, D. W. and Curry, W. B. (2012). Deep Atlantic Circulation During the Last Glacial Maximum and Deglaciation. Nature Education Knowledge, 3(10):1.

Large article at link:  http://www.nature.com/scitable/knowledge/library/deep-atlantic-circulation-during-the-last-glacial-25858002

"Antarctic Bottom Water production by intense sea-ice formation in the Cape Darnley polynya," by K. I. Ohshima et al., Nature Geosci., (2013); doi:10.1038/ngeo1738

Nature Geoscience, (2013); doi:10.1038/ngeo1738

Antarctic Bottom Water production by intense sea-ice formation in the Cape Darnley polynya

• Kay I. Ohshima,
• Yasushi Fukamachi,
• Guy D. Williams,
• Sohey Nihashi,
• Fabien Roquet,
• Yujiro Kitade,
• Takeshi Tamura,
• Daisuke Hirano,
• Laura Herraiz-Borreguero,
• Iain Field,
• Mark Hindell,
• Shigeru Aoki and
•  Masaaki Wakatsuchi

Abstract

The formation of Antarctic Bottom Water—the cold, dense water that occupies the abyssal layer of the global ocean—is a key process in global ocean circulation. This water mass is formed as dense shelf water sinks to depth. Three regions around Antarctica where this process takes place have been previously documented. The presence of another source has been identified in hydrographic and tracer data, although the site of formation is not well constrained. Here we document the formation of dense shelf water in the Cape Darnley polynya (65°–69° E) and its subsequent transformation into bottom water using data from moorings and instrumented elephant seals (Mirounga leonina). Unlike the previously identified sources of Antarctic Bottom Water, which require the presence of an ice shelf or a large storage volume, bottom water production at the Cape Darnley polynya is driven primarily by the flux of salt released by sea-ice formation. We estimate that about 0.3–0.7×10⁶ m³ s⁻¹ of dense shelf water produced by the Cape Darnley polynya is transformed into Antarctic Bottom Water. The transformation of this water mass, which we term Cape Darnley Bottom Water, accounts for 6–13% of the circumpolar total.

At a glance

• Figures

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http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1738.html

4th source of Antarctic Bottom Water pinpointed with help of tagged southern elephant seals

Tagged seals help find missing piece in global climate puzzle

Researchers pinpoint fourth known source of bottom water, a crucial oceanic heat-sink.

• by Richard A. Lovett, Nature News,

24 February 2013

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Southern elephant seals fitted with satellite-linked instruments similar to the one above helped oceanographers map deep currents off Antarctica.

MARTIN BIUW

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By tracking the voyages of elephant seals off Antarctica, and with the help of satellite imaging and undersea sensors, researchers have discovered a long-elusive source for the deep-ocean streams of cold water that help to regulate the Earth's climate.

Antarctic bottom water (AABW) is cold, highly saline water that forms near the shores of Antarctica. Being denser than typical seawater, it sinks to the depths and then moves north insluggish currents that spread across the globe.

Three sources of AABW were known until now. The first, in the Weddell Sea, was found in 1940; two others were found in the Ross Sea and along the Adélie Coast of East Antarctica in the 1960s and ‘70s. But for years, researchers have suggested that these were not the only ones. In particular, water samples from an area called the Weddell Gyre contain atmospheric pollutants known as chlorofluorocarbons (CFCs), indicating that the deep water came into contact with the air far too recently to have been carried there from one of the known AABW sinks.

Now, Kay Ohshima, a physical oceanographer at Hokkaido University in Sapporo, Japan, and his colleagues have traced that water to a fourth AABW source, in the Cape Darnley polynya. Their results are published today in Nature Geoscience¹.

Polynyas are regions of open water near sea ice that are kept from freezing by wind and currents that sweep newly formed ice away. Polynyas have relatively high salinity, because most of the salt in sea water is expelled as it freezes.

Armed with the hypothesis that the missing source might be such a polynya, the researchers used satellite sensors to hunt for polynya regions where ice formed particularly rapidly. When satellite data suggested that Cape Darnley might be a candidate, the researchers moored instruments on the seabed, hoping to spot the descending current. In addition, they relied on data from elephant seals (Mirounga leonina) tagged with instruments that monitor ocean conditions.

“The seals went to an area of the coastline that no ship was ever going to get to, particularly in the middle of winter,” says Guy Williams, a physical oceanographer at the Antarctic Climate and Ecosystems Cooperative Research Centre in Hobart, Australia, and a co-author of the study.

The elephant seals confirmed the researchers' hunch. “Several of the seals foraged on the continental slope as far down as 1,800 metres,” he says, “punching through into a layer of this dense water cascading down to the abyss. They gave us very rare and valuable wintertime measurements of this process.”

The new finding fills a gap in researchers’ understanding of the Southern Ocean’s role in global climate, “including carbon dioxide, temperature, the stability of the Antarctic ice sheet and changes in sea level", says Richard Alley, a geophysicist at Pennsylvania State University in University Park, who was not part of the study.

Still, Williams and Ohshima say that the Cape Darnley polynya represents, at most, about one-eighth of the world’s AABW, and that other, similar sources might remain to be discovered.

Michael Meredith, a polar oceanographer at the British Antarctic Survey in Cambridge, UK, who wrote an accompanying commentary on the study, says that if the total rate of AABW formation declines, the resulting changes in cold-water circulation could have important effects on global climate, letting the ocean depths warm and thereby changing the rate of heat exchange between Antarctica and the tropics. Moreover, he says, sea levels could rise — owing to the fact that water expands as it warms — and temperature changes could affect deep-sea ecosystems.

Nature

 

doi:10.1038/nature.2013.12488

References

1. Ohshima, K. I. et al. Nature Geosci. http://dx.doi.org/10.1038/ngeo1738 (2013).
   
   
   http://www.nature.com/news/tagged-seals-help-find-missing-piece-in-global-climate-puzzle-1.12488

"Closure of the meridional overturning circulation through Southern Ocean upwelling" by John Marshall & Kevin Speer, Nature Geoscience 5 (2012) doi:10.1038/ngeo1391

Nature Geoscience 5 (2012) 171–180; doi:10.1038/ngeo1391

Closure of the meridional overturning circulation through Southern Ocean upwelling

• John Marshall* and
•  Kevin Speer

Received September 22, 2011; accepted January 6, 2012; published online February 26, 2012.


Abstract

The meridional overturning circulation of the ocean plays a central role in climate and climate variability by storing and transporting heat, fresh water and carbon around the globe. Historically, the focus of research has been on the North Atlantic Basin, a primary site where water sinks from the surface to depth, triggered by loss of heat, and therefore buoyancy, to the atmosphere. A key part of the overturning puzzle, however, is the return path from the interior ocean to the surface through upwelling in the Southern Ocean. This return path is largely driven by winds. It has become clear over the past few years that the importance of Southern Ocean upwelling for our understanding of climate rivals that of North Atlantic downwelling, because it controls the rate at which ocean reservoirs of heat and carbon communicate with the surface.

http://www.nature.com/ngeo/journal/v5/n3/abs/ngeo1391.html

Rob Painting, Skeptical Science: Ocean Heat Poised To Come Back And Haunt Us?

Ocean Heat Poised To Come Back And Haunt Us?

by Rob Painting, Skeptical Science, October 15, 2011

Comments about a recent post on Meehl et al. (2011), a climate model-based study, indicated that a number of issues had not been made very clear. For instance, what was meant by natural variability, and what were the mechanisms in the climate model which allowed heat to be distributed to the deep ocean? Hopefully, I can clarify a few things with this additional post. 

The natural variability referred to in the climate model is simply the exchange of heat in the surface and subsurface layers of the ocean, as is apparent in real world observations of La Niña and El Niño. La Niña-like patterns cause cooler-than-average surface temperatures because large areas of cool subsurface oceanic waters are brought to the surface.

And no, this isn't some new, as-yet-unexplained phenomena. The climate model suggests that La Niña and the (La Niña-like) negative phase of the Interdecadal Pacific Oscillation, well-observed ocean patterns, are when large amounts of heat are pumped down into the deep ocean.

Natural variability in a warming world

In a stable climate (i.e., no human-caused global warming, or some other natural climate forcing) the "peaks and valleys" of natural variability in global surface temperatures would average out to zero over the long-term. To get this point across, I've shown this in the graphic below in a very simplified manner -- real-world natural variability, quite obviously, would be much more irregular.  

Figure 1. Diagram illustrating "natural variability" with a long-term average of zero.

The ocean heat content of the real world, however, is steadily increasing, and this affects global surface temperatures. Therefore if we take that natural oscillation, with a long-term average of zero, and now plot it on a warming trend: 

Figure 2. Diagram illustrating "natural variability" with a long-term warming trend.

We now see that the "valleys" become shallower because they are superimposed on a climbing (warming) trend -- these can be thought of as the hiatus decades. But note what happens to the peaks -- they become steeper and higher, with each successive cycle climbing higher than the last.

The work of Meehl et al. (2011) suggests that natural variability persists under conditions of global warming similar to the present, and that we may currently be in one of these decade-long hiatus periods. If so, we likely face a steep climb in global surface temperatures to the next peak of the natural cycle.

The ocean and global surface temperatures

Being in contact with the atmosphere, and covering about 70% of the Earth's surface, the ocean surface layer is the main source of atmospheric heating. The ocean absorbs sunlight and warms during the day, but as it is warmer than the air above it, the oceans release this heat to the cooler atmosphere above. Because of this, the temperature of the ocean surface layers, and the ocean-atmosphere heat exchange, exert a strong influence on global surface temperatures.

La Niña-like, El Niño-like, like what?

These phrases simply describe the characteristic state of the climate over the period observed. During La Niña there is strong upwelling of deeper cooler water in the tropical Eastern Pacific. When enough of this cooler water reaches the surface it causes cooling of global surface temperatures, due to the ocean surface-atmosphere heat exchange and the increased rainfall over land it produces.

The opposing phase in this natural cycle, is El Niño. During El Niño, the upwelling of cooler deep water in the tropical Eastern Pacific shuts off, heat in the surface layers (top 100 metres of ocean) builds up, and the ocean loses heat to the atmosphere. This, and subsequent reduced rainfall over land, results in the rise in global surface temperatures we typically associate with El Niño (see Trenberth, 2002). (There is a great animation of ENSO (La Niña/El Niño) here.)

  

Therefore, if the dominant pattern over a decade is La Niña-like, then we would expect global surface temperatures to stagnate -- the hiatus decades in the model. This is seen in the Pacific Ocean heat content trends from the climate model used by Meehl et al. (2011) below:   

Figure 3. Composite decadal trends of zonal-mean temperature trends for hiatus periods for the Pacific Ocean. From Meehl et al. (2011).

The vertical profile shows heat (the warm-coloured areas in Figure 3) accumulating in the subsurface ocean during the hiatus periods. At the same time the ocean surface, particularly the top 100 metres, shows a cooling trend. It's this La Niña-like cooling trend in the surface layers that stalls global surface temperatures, even though the layers underneath are gaining heat. 

Funneling heat into the deep ocean 

The oceans warm during La Niña-like hiatus periods, but how does heat get into the deep ocean, when much of the surface ocean is cooler-than-normal? Figure 4 (from Meehl et al., 2011) shows the areas of ocean where heat begins to pile up.

Figure 4. Composite average global surface temperature trends for hiatus decades; stipling indicates 5% statistical significance (i.e., a 5% probability the result was due to chance or statistical error). Orange-coloured ocean areas represent regions where OHC is converging and being driven down into the deep.

In the warm-coloured oceanic regions, heat is converging in the surface layers and is being forced down to the deep ocean. An example of this strong downwelling of heat in the model is shown for the upper Pacific Ocean in Figure 5 below.

Figure 5. Composite decadal trends of meridional overturning stream function (i.e., ocean volume transport) for the upper Pacific Ocean for hiatus periods. Arrows added for clarity. Sv= sverdrup (from Meehl et al., 2011).

Again, this is very reminiscent of the upwelling of cool water in the Eastern Pacific, and the pooling of warm water in the Northern Pacific that is observed during La Niña.

No doubt many readers will identify these hiatus periods, as depicted in Figure 4, as similar not only to La Niña but to the pattern that arises during the negative phase of the Interdecadal Pacific Oscillation. In other words, the climate model is simulating well-observed phenomena, although we currently lack the instruments and data to verify all the details. 

One more time

So to recap:

• Meehl e al. (2011) is a climate model-based study showing that hiatus decades, of little or no increase in global surface temperatures, are relatively common, even under conditions of global warming similar to the present.
• This see-sawing pattern of global surface temperatures has been apparent in climate model projections for some time now. 
• These hiatus decades are simply the cool phase of a cool-warm natural cycle where heat is exchanged between the surface and subsurface ocean. 
• The deep ocean warms during these hiatus decades because heat builds up in mid-latitude regions and is quickly funneled downwards.
• Heat buried in the deep ocean remains there for hundreds to thousands of years. It is not involved in the heat exchange occurring in shallower layers. 
• Oceanic patterns in the hiatus decades are very similar to both La Niña and the Interdecadal Pacific Oscillation. So the model is simulating well-observed phenomena.
• The ocean, as a whole, is still steadily building up heat, so the next warm phase of this natural cycle may drive global temperatures to new record highs (the ocean heat coming back to haunt us).  

http://www.skepticalscience.com/Ocean-Heat-Poised-To-Come-Back-And-Haunt-Us-.html

Rob Painting, Skeptical Science: Ocean heat content and the importance of the deep ocean

Ocean heat content and the importance of the deep ocean

by Rob Painting, Skeptical Science, September 24, 2011

Most of the heat from global warming is going into the oceans. Covering some 70% of the Earth's surface and having a heat capacity a thousand times more than the atmosphere, it's easy to understand why the oceans are the main heat sink.

Multiple studies measuring from the ocean surface down to 700 metres show very little warming, or even cooling, over multiple years in the last decade. This is surprising given that some studies estimate that the imbalance at the-top-of-the-atmosphere (TOA), the difference between energy entering and leaving Earth's atmosphere over that time, has actually grown. 

So we might have expected the 700-m sea-surface layer to show increased warming. However, the average depth of the ocean is around 4,300 m, and in a recent SkS post, we saw that when measurements were extended down to 1,500 m, the oceans were found to still be warming, indicating that heat is somehow finding a way down to the deep ocean.

SkS has recently looked at Asian aerosols as a contributor to the 'slowdown' in warming, but a recent climate modeling study (Palmer 2011) suggests another possible cause -- that heat is able to be buried into deeper ocean layers, something the observations seem to support. The study found that there are mechanisms operating in the climate models, over decadal timeframes, which are able to distribute heat to all depths of the ocean. So only measuring down to 700 m does not give an accurate indication of the total amount of heat being absorbed by the oceans.

TOA and OHC 

To examine the relationship between the top-of-the-atmosphere (TOA) and ocean heat, Palmer (2011) used three generations of Hadley Centre climate models and ran multi-century simulations in which the TOA was imbalanced. Three different values for this TOA imbalance arose out the processes inherent in each model -- in other words, the natural variability in the models.

The authors found that it was necessary to integrate OHC from all ocean layers in order to understand what was going on at TOA (see Figure 1). 

Figure 1. The 90% prediction interval for decadal trend in total energy (average TOA in the models) associated with OHC from the surface to deeper ocean layers. As deeper layers of the ocean are included in measurements, the average TOA and OHC show closer agreement. See Palmer (2011) for details.

The three coloured lines represent the three climate models used. The vertical axis is the ocean depth, and the horizontal axis represents the ability of the decadal ocean heat content trend to predict the decadal TOA imbalance trend on 9 out of 10 occasions (90%). By including successively deeper layers of the ocean, the difference between the value of TOA and OHC grows smaller.   

Statistical regression analysis of the results found a weak relationship between sea-surface temperature (SST) and TOA in the climate models (Figure 2a), due to internal variability. Only when the full depth OHC trend was included in the analysis was there found to be a strong relationship between OHC and TOA (Figure 2b). In other words, to account for the heat sequestered in the ocean, we have to measure right to the bottom.

Figure 2. Plot of linear decadal trends in total energy regressed against (a) decadal trends in globally averaged sea surface temperature and (b) decadal trends in full-depth ocean heat content. Note that total energy is equivalent to to the average TOA over the same period. From Palmer (2011).

The ocean is not a bathtub

A common misconception about the oceans seems to be the idea that heat can only travel directly downwards into deeper ocean layers, as if the oceans were only one-dimensional models or perhaps a bathtub. Clearly this isn't the case -- a vast amount of heat is moved around the world's ocean via the Thermohaline Circulation, and science is steadily coming to terms with the many ocean processes which mix heat down into the depths. La Nina is a classic example of how quickly heat from surface layers can be mixed down to the deep, and this is something I'll cover in my next post.

So to sum up:

• Mechanisms exist within climate models, which are capable of mixing heat down to the deep ocean on decadal timeframes.

• Current observations of the 700-m surface layer have shown little warming, or even cooling, in the last 8 years; but the surface layer down to 1,500 m has shown significant warming, which seems to support the modeling    

• Climate modeling and observations indicate that to fully understand the global enery budget (where all the heat is going) we need to include measurements of the deep oceans. The surface layers, even down to 700 m, are not robust indicators of total OHC.
   
  http://www.skepticalscience.com/Ocean-Heat-Content-And-The-Importance-Of-The-Deep-Ocean.html

JPL: Aquarius ields NASA's first global map of ocean salinity

Aquarius Yields NASA's First Global Map of Ocean Salinity

The first global map of the salinity, or saltiness, of Earth's ocean surface produced by NASA's new Aquarius instrument reveals a rich tapestry of global salinity patterns, demonstrating Aquarius' ability to resolve large-scale salinity distribution features clearly and with sharp contrast. NASA/GSFC/JPL-Caltech. › Full image and caption

NASA's JPL, September 22, 2011

PASADENA, Calif. – NASA's new Aquarius instrument has produced its first global map of the salinity of the ocean surface, providing an early glimpse of the mission's anticipated discoveries.

Aquarius, which is aboard the Aquarius/SAC-D (Satélite de Aplicaciones Científicas) observatory, is making NASA's first space observations of ocean surface salinity variations -- a key component of Earth's climate. Salinity changes are linked to the cycling of freshwater around the planet and influence ocean circulation.

"Aquarius' salinity data are showing much higher quality than we expected to see this early in the mission," said Aquarius Principal Investigator Gary Lagerloef of Earth & Space Research in Seattle. "Aquarius soon will allow scientists to explore the connections between global rainfall, ocean currents and climate variations."

The new map, which shows a tapestry of salinity patterns, demonstrates Aquarius' ability to detect large-scale salinity distribution features clearly and with sharp contrast. The map is a composite of the data since Aquarius became operational on August 25, 2011. The mission was launched June 10 from Vandenberg Air Force Base in California. Aquarius/SAC-D is a collaboration between NASA and Argentina's space agency, Comisión Nacional de Actividades Espaciales (CONAE).

"Aquarius/SAC-D already is advancing our understanding of ocean surface salinity and Earth's water cycle," said Michael Freilich, director of NASA's Earth Science Division at agency headquarters in Washington. "Aquarius is making continuous, consistent, global measurements of ocean salinity, including measurements from places we have never sampled before."

To produce the map, Aquarius scientists compared the early data with ocean surface salinity reference data. Although the early data contain some uncertainties, and months of additional calibration and validation work remain, scientists are impressed by the data's quality.

"Aquarius has exposed a pattern of ocean surface salinity that is rich in variability across a wide range of scales," said Aquarius science team member Arnold Gordon, professor of oceanography at Columbia University in Palisades, N.Y., and at the university's Lamont-Doherty Earth Observatory. "This is a great moment in the history of oceanography. The first image raises many questions that oceanographers will be challenged to explain."

The map shows several well-known ocean salinity features such as higher salinity in the subtropics; higher average salinity in the Atlantic Ocean compared to the Pacific and Indian oceans; and lower salinity in rainy belts near the equator, in the northernmost Pacific Ocean and elsewhere. These features are related to large-scale patterns of rainfall and evaporation over the ocean, river outflow and ocean circulation. Aquarius will monitor how these features change and study their link to climate and weather variations.

Other important regional features are evident, including a sharp contrast between the arid, high-salinity Arabian Sea west of the Indian subcontinent, and the low-salinity Bay of Bengal to the east, which is dominated by the Ganges River and south Asia monsoon rains. The data also show important smaller details, such as a larger-than-expected extent of low-salinity water associated with outflow from the Amazon River.

Aquarius was built by NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the Goddard Space Flight Center in Greenbelt, Md., for NASA's Earth Systems Science Pathfinder Program. JPL is managing Aquarius through its commissioning phase and will archive mission data. Goddard will manage Aquarius mission operations and process science data. CONAE provided the SAC-D spacecraft and the mission operations center.

The new map is available at: http://photojournal.jpl.nasa.gov/catalog/PIA14786 .

For more information about Aquarius/SAC-D, visit: http://www.nasa.gov/aquarius andhttp://www.conae.gov.ar/eng/principal.html .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

http://www.jpl.nasa.gov/news/news.cfm?release=2011-300

"Stronger ocean circulation and increased melting under Pine Island Glacier ice shelf " by Stanley S. Jacobs, Adrian Jenkins, Claudia F. Giulivi & Pierre Dutrieux, Nature Geosci., doi: 10.1038/ngeo1188

Nature Geoscience,  doi: 10.1038/ngeo1188

Stronger ocean circulation and increased melting under Pine Island Glacier ice shelf

• Stanley S. Jacobs,
• Adrian Jenkins,
• Claudia F. Giulivi and
•  Pierre Dutrieux

• Received December 1, 2010; accepted May 20, 2011; published online June 26, 2011.

Abstract

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In 1994, ocean measurements near Antarctica’s Pine Island Glacier showed that the ice shelf buttressing the glacier was melting rapidly¹. This melting was attributed to the presence of relatively warm, deep water on the Amundsen Sea continental shelf. Heat, salt and ice budgets along with ocean modelling provided steady-state calving and melting rates^2, 3. Subsequent satellite observations and modelling have indicated large system imbalances, including ice-shelf thinning and more intense melting, glacier acceleration and drainage basin drawdown^{4, 5, 6, 7, 8, 9, 10}. Here we combine our earlier data with measurements taken in 2009 to show that the temperature and volume of deep water in Pine Island Bay have increased. Ocean transport and tracer calculations near the ice shelf reveal a rise in meltwater production by about 50% since 1994. The faster melting seems to result mainly from stronger sub-ice-shelf circulation, as thinning ice has increased the gap above an underlying submarine bank on which the glacier was formerly grounded¹¹. We conclude that the basal melting has exceeded the increase in ice inflow, leading to the formation and enlargement of an inner cavity under the ice shelf within which sea water nearly 4 °C above freezing can now more readily access the grounding zone.

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Link to abstract:  http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1188.html