Overview In 2014, the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project was launched with a vision to enable a transformative shift in scientific and public understanding of the role of the Southern Ocean in climate change and biogeochemistry. This past year was the first year of active spending of the SOCCOM2 award, a 4-year grant that continues the original SOCCOM project to obtain a decade of Southern Ocean observations. In the past 7 years, SOCCOM researchers have: Deployed over 200 biogeochemical floats operating in all 3 basins of the Southern Ocean; Developed a high-resolution biogeochemical Southern Ocean State Estimate (B-SOSE) that is assimilating float data; Calculated float-based climatological seasonal cycles of oxygen, nitrate, and carbon system variables and air/sea carbon fluxes across the Southern Ocean, including seasonal ice zones; Carried out model simulations that suggest a new climate feedback mechanism from Antarctic meltwater Led a Southern Ocean Model Intercomparison Project (SOMIP), simulations from which have already produced significant and unexpected results; Published over 135 manuscripts on SOCCOM technology and early results, including in two AGU special collections Successfully transferred SOCCOM float and sensor technology to the commercial float industry. In addition, a substantial education effort has contributed to the training and education of 18 postdocs, 18 graduate students, and 47 undergraduate students at five different institutions. 56% of these junior researchers have been female and nearly 10% have been participants from under-represented groups, with highest participation of under-represented groups at the undergraduate level. More broadly, SOCCOM’s outreach efforts have engaged thousands of members of the public through online events and via social media with compelling stories highlighting SOCCOM research. With 131 floats adopted so far, the popular Adopt-a-Float program partners teachers and classrooms around the world with SOCCOM researchers by providing students the chance to name and track their very own float and educating them about Southern Ocean biogeochemistry and climate change. 2020 -2021 Progress Observations During 2020-2021, SOCCOM managed to deploy 14 BGC floats from 2 US cruises, on the NB Palmer and Revelle, about half the number that were planned and that we have normally deployed each year. Going to sea during the pandemic was epically difficult. Half of the USAP NB Palmer expeditions that we were relying on were cancelled, and all deployments from non-US vessels were cancelled because of either cancellation of the cruises themselves, or lack of access to ports and shipping for SOCCOM floats. Despite all the difficulties, the USAP organized a small set of cruises that originated in California, with long quarantines and a long steam for the (non-SOCCOM) scientists sailing to their study area in the northern Weddell Sea. The USAP marine technicians deployed 4 floats for SOCCOM on that cruise. UNOLS also managed to schedule a major expedition on the Revelle to the central South Pacific, also originating in a US port. SOCCOM deployed 10 floats from this cruise, in a region where we were much in need of new floats. Restrictions on laboratory occupancy at UW and MBARI, as well as restrictions on occupancy at our primary vendor, Sea-Bird Scientific, also greatly impacted the number of floats that were available for deployment, particularly from the long Palmer transit. All Apex floats were withdrawn from that cruise due to a sensor issue that was likely traceable to the lab restrictions, leaving just 4 Sea-Bird Navis floats. Despite the pandemic, SOCCOM was able to maintain full operations in data processing and management. Our long experience with weekly teleconferencing meant that we were in front of the challenges brought on by nearly universal telecommuting. Physical and biogeochemical observations During quality control of SOCCOM floats it was noted that temperatures below the freezing point of seawater were observed. This led to a seminal paper (Haumann et al., 2020) that describes the frequent observation of supercooled seawater in the Southern Ocean and an assessment of its impacts on the ocean heat flux. Float deployments by SOCCOM have been the basis for development of a method to determine gross oxygen production at the global scale. A manuscript reporting this data has been accepted at Nature Geoscience (Johnson and Bif, 2021). Carbon outgassing in the southern part of the ACC that was originally documented in Gray et al. (2018) was examined anew with the many additional years of data, revealing much stronger outgassing in the Indian and Pacific sectors than in the Atlantic, which we attribute to more vigorous winter entrainment of high carbon waters into the mixed layer (Prend et al., in revision). Processes governing bloom dynamics in the Southern Ocean were assessed using SOCCOM profiling floats (Arteaga et al., 2020). The phenology of phytoplankton blooms relative to sea ice cover and Taylor column dynamics over Maud Rise from both floats and BSOSE showed that net community production is correlated with length of the sea ice-free season, and that the presence of the Maud Rise Taylor column greatly enhances NCP in every year regardless of the presence of a polynya (von Berg et al., 2020). Float technology and data management. A very detailed manuscript describing the protocols developed in SOCCOM for quality control and quality assurance of profiling float data has been accepted (Maurer et al., 2021). A review of autonomous platforms in biogeochemical observations was published (Chai et al., 2020). Protocols and methods developed in SOCCOM for profiling float pH observations have now been extended to gliders (Takeshita et al., 2021). References: von Berg, L., Prend, C. J., Campbell, E. C., Mazloff, M. R., Talley, L. D., & Gille, S. T. ( 2020). Weddell Sea phytoplankton blooms modulated by sea ice variability and polynya formation. Geophysical Research Letters, 47, e2020GL087954. https://doi.org/10.1029/2020GL087954 Haumann, F.Alexander, Ruth Moorman, Stephen C Riser, Lars H Smedsrud, Ted Maksym, Annie PS Wong, Earle A Wilson, Robert Drucker, Lynne D Talley, Kenneth S Johnson, Robert M Key and Jorge L Sarmiento. 2020. Geophysical Research Letters, 47, e2020GL090242. https://doi.org/10.1029/2020GL090242 Fei Chai, Kenneth S Johnson, Hervé Claustre, Xiaogang Xing, Yuntao Wang, Emmanuel Boss, Stephen Riser, Katja Fennel, Oscar Schofield, Adrienne Sutton. 2020. Monitoring ocean biogeochemistry with autonomous platforms. Nature Reviews Earth & Environment, 1, 315–326. https://doi.org/10.1038/s43017-020-0053-y Takeshita, Y., Brent D. Jones, Kenneth S. Johnson, Francisco P. Chavez, Daniel L. Rudnick, Marguerite Blum, Kyle Conner, Scott Jensen, Jacqueline S. Long, Thom Maughan, Keaton L. Mertz, Jeffrey T. Sherman, and Joseph K. Warren. 2021. Accurate pH and O2measurements from spray underwater gliders. J. Atmos. Ocean.Technol. https://doi.org/10.1175/JTECH-D-20-0095.1 Arteaga, L.A., E. Boss, M.J. Behrenfeld et al. (2020). Seasonal modulation of phytoplankton biomass in the Southern Ocean. Nat Commun. 11, 5364. https://doi.org/10.1038/s41467-020-19157-2 Prend, C.J., A.R. Gray, L.D. Talley, S.T. Gille, F.A. Haumann, K.S. Johnson, S.C.Riser, I. Rosso, J. Sauve, and J.L. Sarmiento, 2021. Indo-Pacific sector dominates Southern Ocean carbon outgassing. In revision. Maurer, T. L., J. N. Pland, and K. S. Johnson (2021) Delayed-mode quality control of oxygen, nitrate and pH data on SOCCOM biogeochemical profiling floats. Front. Mar. Sci., accepted. Southern Ocean State Estimate The BSOSE group participated in seven total publications this year. One was an evaluation of mode water export from the Southern Ocean in CMIP6 (Almeida et al, 2021). This paper looked at statistical relationships between air-sea fluxes in these CMIP models and the export, and found significant correlations, but also found the statistics were not stationary in time implying the mode water export response is sensitive to the background climate state. In a simplified modeling experiment Twelves et al. (2020) showed the impact of glacial meltwater and phytoplankton self-shading on biomass and net community production on the Antarctic continental shelf. Self-shading had a large impact, and is now being used in BSOSE production. Additionally the group carried out studies related to observing system design. For example, in Wei et al. (2020) a method was developed to determine where to place platforms to best constrain air-sea heat flux. Meanwhile convergence/divergence and acceleration of Argo floats in the presence of strong Southern Ocean currents was assessed in Wang et al. (2020), and informs biases in Argo sampling and interpretation. The group also carried out development informing data assimilation methods. In Shi et al. (2021) sea ice thickness data was analyzed and compared to reanalyses, including SOSE. Meanwhile Luo et al. (2021) presented an ensemble based Southern Ocean assimilation effort. The latest BSOSE iteration (I135) was released, and covers the period 2013-2019 at ⅙ degree. The BSOSE user base continues to grow, and 10 publications using BSOSE from external research groups were identified this past year. We are also working with Donata Giglio (CU Boulder) to make BSOSE available via ArgoVis (https://argovis.colorado.edu/). This will give users the ability to readily collocate Argo & BSOSE diagnostics. Finally, the BSOSE group is working to make a pH, NO3, and O2 climatology, and anticipates publishing this product in the next reporting cycle. References: von Berg, L., Prend, C. J., Campbell, E. C., Mazloff, M. R., Talley, L. D., & Gille, S. T. ( 2020). Weddell Sea phytoplankton blooms modulated by sea ice variability and polynya formation. Geophysical Research Letters, 47, e2020GL087954. https://doi.org/10.1029/2020GL087954 Wei, Y., S. T. Gille, M. R. Mazloff, V. Tamsitt, S. Swart, D. Chen, and L. Newman, 2020: Optimizing Mooring Placement to Constrain Southern Ocean Air–Sea Fluxes. J. Atmos. Oceanic Technol., 37, 1365–1385, https://doi.org/10.1175/JTECH-D-19-0203.1 Wang, T., Gille, S. T., Mazloff, M. R., Zilberman, N. V., & Du, Y. (2020). Eddy‐induced acceleration of Argo floats. Journal of Geophysical Research: Oceans, 125, e2019JC016042. https://doi.org/10.1029/2019JC016042 Twelves, A. G., Goldberg, D. N., Henley, S. F., Mazloff, M. R., & Jones, D. C. (2021). Self‐shading and meltwater spreading control the transition from light to iron limitation in an Antarctic coastal polynya. Journal of Geophysical Research: Oceans, 125, e2020JC016636. https://doi.org/10.1029/2020JC016636 Shi, Q., Yang, Q., Mu, L., Wang, J., Massonnet, F. and Mazloff, M. Evaluation of Sea-Ice Thickness from four reanalyses in the Antarctic Weddell Sea. The Cryosphere, 15(1). doi: 10.5194/tc-15-31-2021. https://tc.copernicus.org/articles/15/31/2021/ Almeida, L., Mazloff, M. R., & Mata, M. M. (2021). The impact of Southern Ocean Ekman pumping, heat and freshwater flux variability on intermediate and mode water export in CMIP models: Present and future scenarios. Journal of Geophysical Research: Oceans, 126, e2021JC017173. https://doi.org/10.1029/2021JC017173 Luo H, Yang Q, Mu L, Tian-Kunze X, Nerger L, Mazloff M, Kaleschke L, Chen D (2021). DASSO: a data assimilation system for the Southern Ocean that utilizes both sea-ice concentration and thickness observations. Journal of Glaciology 1–6. https://doi.org/10.1017/jog.2021.57 Modeling The SOCCOM Modeling group led and participated in seven publications this year. Beadling et al. (2020) is a first-of-its-kind, cross-generational analysis of the evolution of the community-wide effort to simulate the Southern Ocean. This study lays out the significant progress made (as quantified by observational-based metrics and comparisons to the state estimate) from the CMIP3 efforts 15 years ago to the CMIP6 simulations today with respect to the Antarctic Circumpolar Current and several other metrics. It also notes several persistent systematic biases that still remain which are likely to affect the simulation and interpretation of biogeochemical trends in the Southern Ocean moving forward. A landmark study by Schlunegger et al. (2020) demonstrates that the invasion of atmospheric carbon is consistently discernible over internal model variability in the Southern Ocean significantly sooner than either ecosystem-controlled parameters (chlorophyll and export production) or hydrologically driven components (salinity). This study builds upon previous work (Schlunegger et al. 2019) that indicated the pH changes observed by the SOCCOM array are the first and strongest indication of a Southern Ocean biogeochemical trend. A series of data assimilative experiments (Swierczek et al. 2021) have provided insight into the complex circulation and mixing regimes within the Argentine Basin, as well as the notorious difficulties associated with simulating it correctly. This study compared the effects of increasing horizontal and vertical resolution and found that it enhances the upward vertical transport and surface exchanges of heat and enhances the downward transport of anomalous DIC although increased resolution caused no significant effect on surface carbon fluxes. A second study (Lockwood et al. 2021) also explored the effects of increased resolution, but focused on the Weddell Sea polynya and the Antarctic Slope Current. This study showed that in response to warming, the slope front in the higher resolution simulation restricts the outflow of lower salinity surface waters due to ice melt thereby maintaining the weak open-ocean stratification tied to polynya formations. The coarser CMIP5 simulations allowed the increased melt to weaken the open ocean stratification and reduced the occurrence of the polynya. They conclude that an improved representation of Weddell Sea shelf processes in current climate models is desirable to increase our ability to predict the fate of the Weddell Sea polynyas under climate change. In addition, the ‘Antwater/Stress’ experiments from the Southern Ocean Model Intercomparison Project (now part of the officially-designated CMIP6 Flux Anomaly Forced Model Intercomparison Project, FAFMIP) have been carried out in both the GFDL-CM4 and GFDL-ESM4 models. The first results of these experiments demonstrate the strong influence that the Antarctic Slope Current has on governing changes along the shelf, highlighting the importance of coupling interactive ice sheet models to ocean models that can resolve these dynamics. In a pair of papers on changes in Southern Ocean circulation, Shi et al. (2020, 2021) have shown from satellite altimetry and historical/Argo time series that the zonally averaged ACC has accelerated, and that the acceleration is attributable to changes in the buoyancy distribution due to much greater heat accumulation north of the ACC compared with south of the ACC. The buoyancy driven acceleration is baroclinic, intensified in the upper ocean, and dominates the surface current acceleration. Wind stress increases have induced a more barotropic acceleration in transport. References: Beadling, R.L., J.L. Russell, R.J. Stouffer, M. Mazloff, L.D. Talley, P.J. Goodman, J.B. Sallée, H.T. Hewitt, P. Hyder, and A. Pandde, 2020: Representation of Southern Ocean properties across Coupled Model Intercomparison Project generations: CMIP3 to CMIP6. J. Climate, 33(15), 6555–6581. https://doi.org/10.1175/JCLI-D-19-0970.1 Schlunegger, S., K.B. Rodgers, J.L. Sarmiento, J.L., Ilyina, T., Dunne, J.P., Takano, Y., Christian, J.R., Long, M.C., Frölicher, T.L., Slater, R. and Lehner, F., 2020: Time of Emergence and Large Ensemble Intercomparison for Ocean Biogeochemical Trends. Global Biogeochem. Cycles, 34: e2019GB006453. https://doi.org/10.1029/2019GB006453 Lockwood, J.W., C.O. Dufour, S.M. Griffies, and M. Winton, 2021: On the role of the Antarctic Slope Front on the occurrence of the Weddell Sea polynya under climate change. J. Climate, 1-56, https://doi.org/10.1175/JCLI-D-20-0069.1 Swierczek, S., M.R. Mazloff, M. Morzfeld, M., and J.L. Russell, 2021: The effect of resolution on vertical heat and carbon transports in a regional ocean circulation model of the Argentine Basin. Journal of Geophysical Research: Oceans, 126, e2021JC017235. https://doi.org/10.1029/2021JC017235 Beadling, R.L., J.P. Krasting, S.M. Griffies, W.J. Hurlin, B. Bronselaer, J.L. Russell, J.-E. Tesdal and M. Winton, Importance of the Antarctic Slope Current on the transient response of the Southern Ocean to Antarctic ice sheet melt and projected wind stress change, J. Geophysical Research – Oceans, (Submitted April 2021) Shi, J.-R., L.D. Talley, S.-P. Xie, W. Liu, S. T. Gille, 2020. Effects of buoyancy and wind forcing on Southern Ocean climate change. J. Climate, 33(23), 10003-10020. doi:10.1175/JCLI-D-19-0877.1 Shi, J.-R., L. D. Talley, S.-P. Xie, Q. Peng, and W. Liu, 2021. Acceleration of the Southern Ocean zonal flow. In revision. Broader Impacts Highlights from the year’s Broader Impacts activities include: Adopt-a-Float program all 14 floats deployed this year were adopted 24 virtual Adopt-a-Float presentations were given to 10 different schools in 7 states and reached around 500 students Social Media 1,790+ followers on Twitter (up 19%) 1,530+ followers on Facebook (up 11%) 495+ followers on Instagram (up 52%) 145+ followers on YouTube (new) Multimedia resources 2 SOCCOM videos produced 1 video abstract produced Video abstract toolkit produced Science communication training SciComm resource page created Hosted COMPASS scicomm workshop for early career SOCCOM scientists
