Interesting Paper on Sea Level Rise – Purkey et al (2014)

Please see the Update at the end of the post to avoid confusion.

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The paper Purkey et al. (2014) Relative contributions of ocean mass and deep steric changes to sea level rise between 1993 and 2013 was recently accepted for publication at the Journal of Geophysical Research: Oceans. The abstract reads (my boldface):

Regional and global trends of Sea Level Rise (SLR) owing to mass addition centered between 1996–2006 are assessed through a full-depth SLR budget using full-depth in-situ ocean data and satellite altimetry. These rates are compared to regional and global trends in ocean mass addition estimated directly using data from the Gravity Recovery and Climate Experiment (GRACE) from 2003–2013. Despite the two independent methods covering different time periods with differing spatial and temporal resolution, they both capture the same large-scale mass addition trend patterns including higher rates of mass addition in the North Pacific, South Atlantic, and the Indo-Atlantic Sector of the Southern Ocean, and lower mass addition trends in the Indian, North Atlantic, South Pacific, and the Pacific Sector of the Southern Ocean. The global mean trend of ocean mass addition is 1.5 (±0.4) mm yr-1 for 1996–2006 from the residual method and the same for 2003–2013 from the GRACE method. Furthermore, the residual method is used to evaluate the error introduced into the mass budget if the deep steric contributions below 700, 1000, 2000, 3000, and 4000 m are neglected, revealing errors of 65%, 38%, 13%, 8% and 4% respectively. The two methods no longer agree within error bars when only the steric contribution shallower than 1000 m is considered.

The full paper (preprint) is here.

I suspect the high rate of sea level rise east of Indonesia the Philippines (shown in the trend map below from the University of Colorado) is the reason the North Pacific trend discussed in the paper is so high with respect to the South Pacific. That pocket of exceptional sea level rise in the western tropical North Pacific looks suspiciously like an ENSO residual (the residuals from a series of off-equatorial Rossby waves returning leftover warm water from El Niño events). I’ve always wanted to remove that portion of the data to see its impact on global sea levels.

Sea Level Trends Univ of Colorado

Sea Level Map from University of Colorado.

I recently expressed my opinion about sea level in the post Maybe It’s Time We Stopped Wasting Money Studying a Problem And Spent That Money Adapting to It. I’ll let you provide additional comment on this paper.

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UPDATE: Please read the paper carefully. The 1.5mm/year trend is the MASS component. In other words, it’s the TOTAL rate of sea level rise MINUS the STERIC (thermal and saline) component.


About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
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6 Responses to Interesting Paper on Sea Level Rise – Purkey et al (2014)

  1. Werner Kohl says:

    Hi Bob, I’m not sure if understand it right: This paper tells us that we have a global sea level rise of about 1.5 mm/y? Not the (if I remember right) 3.2 mm/y what IPCC told us or even more what Rahmstorf thinks? Does this mean that the “corrections” for Jason/TOPEX were incorrect? Wow!

  2. Bob Tisdale says:

    Hi Werner, The 1.5 mm/ year trend is the mass component, not the thermal.

  3. Werner Kohl says:

    Okay, thanks!

  4. Tom O says:

    By “mass component,” I gather they are discussing the volume of ice that has melted and drained off into the oceans? Or pumped aquifer water that has returned to the sea but not as yet back to the aquifers? All this while the glaciers and icecaps appear to be growing?

    And am I reading that color bar correctly, and that there is a difference of surface height off Newfoundland of about 12 mm from east of it to south of it, and a difference from the Philippines to the Baja of over 20 mm?

  5. Bob Tisdale says:

    Tom O, your first paragraph appears to be statements disguised as questions so I’ll pass those. And with respect to your estimates, they appear reasonable.

  6. Thanks, Bob. We keep on learning about the ocean.

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