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Scientists in focus – Lyman and Johnson explore the rapidly warming oceans
Posted on 12 June 2014 by John Abraham
One benefit of working in the climate science arena is that I have the privilege to interact with some of the world’s most talented individuals. I have learned their stories while we have shared hypotheses about how the Earth works. I hope this will be the first in a series of articles showcasing the personal stories of some of the most impactful scientists today.
Among my first entries into climate research was through ocean measurements. A number of years ago, I met Drs. John Lyman and Greg Johnson. These colleagues have worked to modernize our understanding of the oceans and their role in climate change. I wanted to know how they become scientists and what they see over the horizon in their field.
I asked John Lyman, who is affiliated with JIMAR/University of Hawaii and NOAA’s Pacific Marine Environmental Laboratory, how he got into studying the oceans.
"I have always been interested in the ocean. Before entering college, my dad and I went on a trip to the west coast to visit schools. On the trip we had a chance to visit with Walter Munk at Scripps. I asked him about Oceanography as an undergraduate and he strongly discouraged me. He told me that you should have a strong background in a basic science first; math, physics, biology or chemistry. So that’s what I did. I studied physics and somewhere along the line forgot about oceanography. After college I joined the Peace Corps in an attempt to give something back. I ended up teaching math in Zimbabwe. It gave me time to think. At the end of two-years of teaching I found myself reading up on oceanography again. I applied to grad school from Africa, got a Ph.D., and eventually found my way to climate science."
I also asked John what the emerging understanding of oceanography is and what important projects were ongoing. He responded,
"Deep Argo! Most of the world oceans under 2000 meters are woefully under-sampled. Deep Argo will extend the Argo array to the bottom and for the first time we will be able to resolve most of the large-scale variability in the world’s oceans. We will be able to resolve how much heat is really going deep. There is also the added excitement of exploring an area of the world that so little is known about and being the first to describe it."
John Lyman, relaxing (photo courtesy of Gabriel Cisneros)
While John has made many great contributions to the field, he is most fond of two items in particular. The first is a major study he had published in Nature that described and quantified warming of the oceans and another study that was written while a post-doc that used a simple stability model to describe tropical waves; these waves are important to the ENSO process.
I put the same questions to Greg, an oceanographer at the Pacific Marine Environmental Laboratory, and an affiliate professor with the University of Washington. He told me that he went into oceanography because he,
“wanted to combine my interest in physics with my love of the sea. For the first decade or so of my career, I studied mostly ocean temperature, salinity, and currents, and their variability. However, as time has gone on, the importance to climate variations over seasons to millennia have become increasingly apparent, and important in my work.”
Greg Johnson
Johnson's research is important because,
"With the buildup of greenhouse gasses in the atmosphere, more energy enters the Earth environment than escapes. Over the last 4 decades, 93% of this energy imbalance has warmed the ocean, with about 3% warming the land, 3% melting ice, and 1% warming and adding moisture to the atmosphere. Warmed oceans also expand, raising sea level. Hence measuring how much the oceans are warming and where is important to understanding how much and how fast the Earth will warm and sea level will rise."
Greg and his team collect much of their data using Conductivity-Temperature-Depth instruments (CTDs for short). They make accurate measurements of the ocean waters. The CTDs are positioned on autonomous floats (Argo floats), lowered on ship-borne cables, or even attached to marine animals. He also says,
“In my research, I also use data from many other sources including sea level, sea-surface-temperature, sea-surface-salinity, winds, and even ocean mass variations from satellites. I also use current data from drifting buoys, Argo floats, and various types of current meters including acoustic Doppler instruments.”
If all this extra heat is going into the oceans, shouldn't we expect to see accelerated rates of sea level rise? Has this been happening?
(Rob P) - Sea level rise over the last two decades shows that the so-called 'pause'; is non-existent. Cazenave et al (2014) demonstrates that, once you allow for the effects of year-to-year variability of water mass storage on land, sea level has risen at a near-steady rate through the 1990's (3.1mm per year) and 2000's (3.3mm per year).
Acceleration is not evident for this period because sea level rise increased quickly during the early 2000's, slowed between 2004-2008, and has sped up again since then. This likely due to the observed global dimming during the early to middle 2000's.
See here. For breakdown on the components to sealevel rise, see here.
Actually, I think Austrartsua's question arises from a more basic problem, arising from a lack of clarity on our part. When we say more heat has been going into the oceans, what we are actually saying is that a greater proportion has been going into the ocean.
Because the oceans already take up the vast bulk of the heat, a significant drop in the amount of heat being taken up by the atmosphere leads to a negligible increase in the amount of heart taken up by the oceans. Thus we would not expect to see a change in the rate of sea level rise.
@Austrartsua #1 If I take 0.00016 as a rough estimate of average ocean thermal expansion coefficient weighted by more warming in upper half, then I compute 0.111 mm SLR per Zettajoule, so 1.52 mm/yr 2000-2012 then 2.82 mm SLR for 2013. However, Dr. Trenberth mentions that ice melt gives ~50x as much SLR bang for the heating buck as thermal expansion. I compute ice melt would yield 9.18 mm SLR per Zettajoule, which is 83x my thermal expansion estimate. Of course, the heat must reach the ice to accomplish this. Peter Sinclair mentioned 624 Gt/yr global ice melt now in some video (I had previously thought it was 300-400) which would be 1.72 mm SLR. My point is that ice melt is now approximately half of the SLR signal and will increase to an overwhelming proportion over the next several decades and centuries so attempting to measure OHC increase by SLR increase will become increasingly problematic and unneccessary in my opinion, it's better just to stay with the actual measurements, especially if the people who control the money eventually start dumping lots more CTDs in the oceans.