A bus trip to the bottom of the ocean with Genghis and Cesar

This post described the 20th day of a voyage as part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). It was one of many posts I made for a blog describing that voyage where we saw many seals, whales and even a polar bear*...(*late March/early April was particularly eventful) check it out at http://dimesuk4.blogspot.com.au.

The wind howled last night. As the second last mooring was dropped back into the water the wind picked up to 50 knots. The snow and ice whizzed past as did the sea ice - large slabs colliding with the ship from time to time. The forecast said we’d be bunkered down for the next 3 days.  If you think forecasts in Southern England or Tasmania are poor....try the tip of Antarctica. It worked out in our favour today as we were able to finish off the last of our work here and are now preparing to head east - out of the ice.

Photo: It will be sad to leave the ice-scape tonight.

During the last week we have been recovering and deploying moorings which are measuring the flow of Bottom Water off the coast of Antarctica. The tracer team have also been measuring the amount of CFCs in the water. Sorry to lay on yet another three letter acronym (TLA) on you. You may have heard about Chlorofluorocarbons and how they have been causing the whole in the ozone layer to get bigger. Liking to put a positive spin on the situation, us oceanographers have found a great use for them: they tell us how ‘old’ the water is.

Photo: Fat seals...because they are cute. 

I spoke to Andy Watson from the University of East Anglia, the trace gas expert, about this today. Any given layer of water is made up of a mixture of water from different places and times. Different kinds of CFCs have been in the air at differnt times, so if we know how much of each is in different layers of the ocean we can tell how old the water is...on average.

Knowing the average age of the water at a given level in the ocean is a bit like knowing the average age of all the people on a bus. If the bus is heading to kindergarten there will be mostly young kids and maybe the bus driver and/or someones mother who will bring up the age a little. An outing from an old-persons home will of course be the other way around. We only know the average age of the water at each level in the ocean and use this along with the other measurements we take to figure out where they’ve come from and where they are going:

Surface Ocean (0-200m deep): Bus from the maternity ward at the local hospital (babies with a few young mothers and nurses)
Upper Ocean (200 -1000m deep): Young professionals on their way to work, sharing the bus stop with retirees on their way back from the shops.
Middle Ocean: (1000m-3000m deep) Genghis Kahn shares the bus with Oliver Cromwell, Julius Cesar and friends.
Deep Ocean: (3000m – 6000m) Early humans and the odd dinosaur take the slow bus to Bognor Regis with the odd bus load of teenagers flying through for a Stag Night in Brighton.

The bus load of teenagers is the newly created Antarctic Bottom Water - sinking rapidly into the deep ocean.

Photo: Colourful plots of the data from the different CFCs indicating the average age of the water. Red means toddler, blue means middle aged and pink means Julius Cesar. The blue bit at the bottom is the relatively young Antarctic Bottom Water flowing out through Orkney Passage.

Why climate science needs more lunatics

This blog was originally written for the Grantham Institute - Climate Change and the Environment

In 1560, our moon did something that it does only every generation or so. As it circled the Earth at a stately pace of one rotation per 27 days, it found itself directly between us and the Sun. This cast a great shadow over Europe, causing great panic.

Remarkably for this period, 400 years before humans left the Earth and set foot on the dusty lunar surface, this mystical and awe-inspiring occurrence was predicted by the Copernican model of the cosmos. Moved by the power of this new science, an unassuming young Danish scholar called Tycho Brahe decided to dedicate his superior intellect to studying the stars.

Tycho Brahe

He fast became one of great thinkers of the Renaissance and was one of the first to question the belief that the universe is unchanging. Now in 2015, our home planet is at risk from the less visible, but far less benign shadow of climate change. Are we due a new generation of Brahes, great thinkers who can propel our understanding forward?

There is no better test of a science than its ability to make and verify predictions. In the late 19th century, Arheneous first proposed a theory that a blanket of certain gases in the atmosphere was helping to insulate the planet. Over a century later, there is still an astronomical amount we don’t fully understand about our planet’s climate system.

A delicate heat balance

The climate turns out not to be as predictable as Brahe’s eclipse. We humans exist within a thin fraction of the climate system; typically experiencing winds from the lowest kilometre of the atmosphere and ocean currents from the shallowest 50 metres of the ocean.

We can think of the temperature in this zone like a variable bank balance. Solar radiation deposits a continuous stream of income, heat radiated out to space is like our regular spending, and savings are made for a later date as heat deposited into the deep ocean.

Basic physics tells us that greenhouse gases reduce the amount of heat lost to space. In the absence of other effects, the balance of heat grows in the thin layer we occupy. Just as unexpected bills affect our own bank balance though, a plethora of changeable processes affect Earth’s surface temperature.

The ocean as a heat sink

One of these processes, which sees heat being stored in the ocean, can lead to a slowing and even temporary reversal of surface warming. Between 1997 and 2014, the earth did warm, but at a slower pace than it had before – in large part due to increased storage of heat in the ocean – the reasons for which we discuss in a recent Grantham briefing paper.

From studying this period of slower warming we have learnt a great deal about the climate system, including that the winds along the equator that expose deep cold water to the surface are more variable from decade to decade in the real climate than in the computer models that have so far been used to predict future temperatures.

Cycles in the oceans’ circulation are now giving back some of this heat, and aided by a record El Niño, 2015 is most likely to be earth’s warmest year on record. Continuing the trend from 2014, the current title-holder according to the World Meteorological Organisation. The prediction, made by scientists in the 1970s and 80s, and heard by the public at large in the 1990s, is emerging once again.

What’s the forecast?

Ocean circulation may still cause the decade following this one to be cooler than the present. It could also be far, far warmer, we don’t yet know. The same goes for the plethora of processes, which affect the surface temperature and climate at large scales. The list of largely unpredictable phenomena includes the physics of clouds, the effect of erupting volcanoes, variability in radiation from the sun and the cooling effects of atmospheric pollutants.

To help understand and predict these effects better we need the support of public and private donors and we need great minds to take to climate science in 2015, like Tycho Brahe took to astronomy in the 1560.

Regardless of whether the COP21 meeting in Paris yields significant pledges to cut greenhouse gas emissions, understanding of climate science will become more and more important.

As the Grantham Institute’s climate prediction tool shows, pledges from governments, put the world on course for well over 2oC of global warming.

Brahe may have become an astronomer on the basis of a visible yet benign prediction. The predictions made about the effects of the changing climate have been less visible but are becoming less and less benign. Let us hope the Tycho Brahes of today have been taking note.

My name is Jan Zika, I am a physicist, oceanographer and general maths nerd who is interested in 

climate change and other important global questions. I am based at the University of New South Wales.

I am on twitter (@JanDZika) and you can email me (j.zika@unsw.edu.au).

The Olympic One Percent

When I saw tables for the Rio Olympic Games which ranked countries by medals per person (e.g. www.medalspercapita.com) I wondered how small highly successful countries contribute to global population and how larger countries do relative to the each other on this measure.

In my medal tally countries are ranked by the number of medals per capita. This is the length of each bar below. What I have done differently is show the population as the thickness of each bar. This way one can see what percentage of the global population different countries fit into. The area of each bar (its length multiplied by its thickness) is proportional to the number of medals. The number of medals is also shown in brackets. A few countries, e.g. Grenada, had so many medals per person (one Silver Medal for a population of only 106,000 people), I had to cut the graph in two at 12 medals per million people.

A number of small countries including New Zealand, Jamaica, Denmark and my country of birth, Australia^, fall into the top 1% with 14.4% of all the medals. Britain, France and Canada are part of the first 5% of the population with nearly 40% of the medals. A number of European countries, the United States, Japan and notably Kenya are in the remaining 20% and by now we have covered more than 80% of the medals. Then come the highly populous middle income countries such as the hosts Brazil as well as Iran and China.

I did not post this graph to gloat though. It is sobering. The final 50% of the world has less than 2.1% of the olympic medals. India has just one silver and one bronze despite a population of 1.3 billion. A further 1.46 billion people* from 121 mostly small and disproportionately African nations+ have zero medals to celebrate.

My name is Jan Zika, I am a physicist, oceanographer and general maths nerd who is interested in climate change and other important global questions. I am based at the University of New South Wales. 

I am on twitter (@JanDZika) and you can email me (j.zika@unsw.edu.au).

^ Actually by the time you count Australia's entire population you get to 1.06% of the world's people. Still not bad.

* The remaining population was calculated by subtracting the sum of populations of medal countries from 7.4 billion.

+ The number of non medal countries was calculated by subtracting the number of medal countries from the total number of competing nations (207 according to wikipedia)