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The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2017-84
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
19 May 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal The Cryosphere (TC) and is expected to appear here in due course.
Methanesulfonic acid (MSA) migration in polar ice: Data synthesis and theory
Matthew Osman1, Sarah B. Das2, Olivier Marchal2, and Matthew J. Evans3 1Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanography/Applied Ocean Sciences and Engineering, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA
2Dept. of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
3Dept. of Chemistry, Wheaton College, Wheaton, MA, USA
Abstract. Methanesulfonic acid (MSA; CH3SO3H) in polar ice is a unique proxy of marine primary productivity, synoptic atmospheric transport, and regional sea ice behavior. However, MSA can be mobile within the firn and ice matrix, a post-depositional process that is well known but poorly understood and documented, leading to uncertainties in the integrity of the MSA paleoclimatic signal. Here, we use a compilation of 22 ice core MSA records from Greenland and Antarctica and a model of soluble impurity transport in order to comprehensively investigate the vertical migration of MSA from summer layers, where MSA is originally deposited, to adjacent winter layers in polar ice. The shallowest depths of MSA migration reported in our compilation vary over a wide range (~ 2 m to 400 m), and our analysis suggests that these depths are positively correlated with snow accumulation rate and negatively correlated with ice concentration of Na+ (typically the most abundant cationic sea salt).

Although the considered soluble impurity transport model provides a useful mechanistic framework for studying MSA migration, it remains limited by inadequate constraints on key physicochemical parameters, most notably, the diffusion coefficient of MSA in cold ice (DMS). We derive a simplified version of the model, which includes DMS as the sole parameter, in order to illuminate aspects of the migration process. Using this model, we show that the progressive phase alignment of MSA and Na+ concentration peaks observed along a high-resolution West Antarctic core is most consistent with 10–12 m2 s-1 < DMS < 10–11 m2 s-1, one order of magnitude greater than DMS values previously estimated from laboratory studies. More generally, our data synthesis and model results suggest that (i) MSA migration may be fairly ubiquitous, particularly at coastal and (or) high accumulation regions across Greenland and Antarctica, and (ii) can significantly change annual and multi-year MSA concentration averages. Thus, in most cases, caution should be exercised when interpreting polar ice core MSA records, although records that have undergone severe migration could still be useful for inferring decadal and lower-frequency climate variability.


Citation: Osman, M., Das, S. B., Marchal, O., and Evans, M. J.: Methanesulfonic acid (MSA) migration in polar ice: Data synthesis and theory, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-84, in review, 2017.
Matthew Osman et al.
Matthew Osman et al.

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Short summary
We combine a synthesis of 22 ice core records and a model of soluble impurity transport to investigate the enigmatic, post-depositional migration of methanesulfonic acid (MSA) in polar ice. Our findings suggest that migration may be universal across coastal regions of Greenland and Antarctica, though is mitigated at sites with higher accumulation and (or) lower impurity content. Records exhibiting severe migration may still be useful for inferring decadal and lower-frequency climate variability.
We combine a synthesis of 22 ice core records and a model of soluble impurity transport to...
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