PhD project(2015-) Yangyang Liu funded by the China Scholarship Council (CSC)

Phytoplankton, the main primary producers at the base of marine food web, have distinctive impacts on the changes of Arctic climate system. The Arctic region is warming at rates double than the global average, coinciding with persistent sea ice decline [1]. Seasonal sea ice cover retreat favors phytoplankton bloom development and the extension of phytoplankton growing season, increasing annual mean phytoplankton biomass and production [2,3]. This increase, in turn, is expected to further warm the ocean surface layer by absorbing more solar radiation and triggering additional positive feedbacks, which could amplify Arctic warming by 20% [2]. Meanwhile, together with ice algae, the increasing phytoplankton stocks generate more dimethylsulphide, a trace gas that provides 80% of global biogenic atmospheric sulphur [4]. When released to the atmosphere, dimethylsulphide, via formation of sulphate aerosol, cool the Arctic atmospheric temperature by dispersing solar radiation [5-7]. The shipboard underway spectrophotometry represents a promising in situ observation technique of phytoplankton biomass and functional types. It utilizes a WET Labs AC-S hyperspectral spectrophotometer (or its former alternative, the 9-wavelength resolved AC-9) that is operated in flow-through mode to derive particulate absorption coefficients (ap) [8-19]. Chl-a, the proxy of phytoplankton biomass, together with phytoplankton functional types, are then derived from ap.

First results for the project have been published in Liu et al. (2018) show the capability of obtaining highly resolved surface Chl-a and phytoplankton functional types (PFT) using shipboard underway AC-S flow-through system in the Fram Strait. These quality-controlled datasets are finally used to validate the quality of the Chl-a datasets of several satellite sensors and assess various satellite Chl-a algorithms and numerical model outputs of PFT.

Publication within PhD thesis:

 

Liu. Y., Roettgers R., Ramírez-Pérez M., Dinter T., Steinmetz F., Noethig E.-M., Hellmann S., Wiegmann S., Bracher A. (in press 22 Jan 2018) Underway spectrophotometry in the Fram Strait (European Arctic Ocean): a highly resolved chlorophyll a data source for complementing satellite ocean color. Optics Express

 

Other references:

1. T.F. Stocker, D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley, Climate change 2013: The physical science basis: Working Group I contribution to the Fifth assessment report of the Intergovernmental Panel on Climate Change (Cambridge University Press, 2013).

2. J.Y. Park, J.S. Kug, J. Bader, R. Rolph, and M. Kwon, “Amplified Arctic warming by phytoplankton under greenhouse warming,” Proc. Natl. Acad. Sci. 112(19), 5921-5926 (2015).

3. K.R. Arrigo and G.L. van Dijken, “Continued increases in Arctic Ocean primary production,” Prog. Oceanogr. 136, 60-70 (2015).

4. A.J. Kettle and M.O. Andreae, “Flux of dimethylsulfide from the oceans: a comparison of updated data sets and flux models,” J. Geophys. Res. 105, 26793-26808 (2000).

5. M. Levasseur, “Impact of Arctic meltdown on the microbial cycling of Sulphur,” Nat. Geosci. 6(9), 691 (2013).

6. R.Y.W. Chang, S.J. Sjostedt, J.R. Pierce, T.N. Papakyriakou, M.G. Scarratt, S. Michaud, M. Levasseur, W.R. Leaitch, and J.P. Abbatt, “Relating atmospheric and oceanic DMS levels to particle nucleation events in the Canadian Arctic,” J. Geophys. Res. Atmos. 116(D17), D00S03 (2011).

7.  P. Tunved, J. Ström, and R. Krejci, “Arctic aerosol life cycle: linking aerosol size distributions observed between 2000 and 2010 with air mass transport and precipitation at Zeppelin station, Ny-Ålesund, Svalbard,” Atmos. Chem. Phys. 13(7), 3643-3660 (2013).

8. G. Dall'Olmo, T.K. Westberry, M.J. Behrenfeld, E. Boss, and W.H. Slade, “Significant contribution of large particles to optical backscattering in the open ocean,” Biogeosciences, 6(6), 947-967 (2009).

9. G. Dall’Olmo, E. Boss, M.J. Behrenfeld, and T.K. Westberry, “Particulate optical scattering coefficients along an Atlantic Meridional Transect,” Opt. Express 20(19), 21532-21551 (2012).

10. T.K. Westberry, G. Dall’Olmo, E. Boss, M.J. Behrenfeld, and T. Moutin, “Coherence of particulate beam attenuation and backscattering coefficients in diverse open ocean environments,” Opt. Express 18(15), 15419-15425 (2010).

11. W.H. Slade, E. Boss, G. Dall’Olmo, M.R. Langner, J. Loftin, M.J. Behrenfeld, C. Roesler, and T.K. Westberry, “Underway and moored methods for improving accuracy in measurement of spectral particulate absorption and attenuation,” J. Atmos. Ocean. Tech. 27, 1733-1746 (2010).

12. E. Boss, M. Picheral, T. Leeuw, A. Chase, E. Karsenti, G. Gorsky, L Taylor, W. Slade, J. Ras, and H. Claustre, “The characteristics of particulate absorption, scattering and attenuation coefficients in the surface ocean; Contribution of the Tara Oceans expedition,” Methods in Oceanography 7, 52-62 (2013).

13. A. Chase, E. Boss, R. Zaneveld, A. Bricaud, H. Claustre, J. Ras, G. Dall’Olmo, and T.K. Westberry, “Decomposition of in situ particulate absorption spectra,” Methods in Oceanography 7, 110-124 (2013).

14. R.J. Brewin, G. Dall'Olmo, S. Pardo, V. van Dongen-Vogels, and E.S. Boss, “Underway spectrophotometry along the Atlantic Meridional Transect reveals high performance in satellite chlorophyll retrievals,” Remote. Sens. Environ. 183, 82-97 (2016).

15. A. Lindfors, K. Rasmus, N. Strömbeck, “Point or pointless—quality of ground data,” Int. J. Remote Sens. 26(2), 415-423 (2005).

16. S. Koponen, J. Attila, J. Pulliainen, K. Kallio, T. Pyhälahti, A. Lindfors, K. Rasmus and M. Hallikainen, “A case study of airborne and satellite remote sensing of a spring bloom event in the Gulf of Finland,” Cont. Shelf Res. 27(2), 228-244 (2007).

17. G. Dall'Olmo, E. Boss, M.J. Behrenfeld, T.K. Westberry, C. Courties, L. Prieur, M. Pujo-Pay, N. Hardman-Mountford and T. Moutin, “Inferring phytoplankton carbon and eco-physiological rates from diel cycles of spectral particulate beam-attenuation coefficient,” Biogeosciences 8, 3423-3440 (2011).

18. P. J. Werdell, C.W. Proctor, E. Boss, T. Leeuw and M. Ouhssain, “Underway sampling of marine inherent optical properties on the Tara Oceans expedition as a novel resource for ocean color satellite data product validation,” Methods in Oceanography 7, 40-51 (2013).

19. G. Dall’Olmo, R.J. Brewin, F. Nencioli, E. Organelli, L. Lefering, D. McKee, R. Röttgers, C. Mitchell, E. Boss, A. Bricaud and G. Tilstone, “Determination of the absorption coefficient of chromophoric dissolved organic matter from underway spectrophotometry,” Opt. Express 25(24), 1079-1095 (2017).

Figure 1. Comparison between Chl-a data obtained from underway AC-S flow-through system and HPLC measurements during the Fram Strait cruises PS93.2 and PS99.2.