Melissa Chierici. Institute of Marine Research And Professor at University Centre in Svalbard (UNIS) Norway

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1 Future challenges to fill the gaps in the marine chemistry and the ocean s capacity for atmospheric CO 2 sequestration in the Atlantic sector of the Southern Ocean Melissa Chierici Institute of Marine Research And Professor at University Centre in Svalbard (UNIS) Norway Contributions from: Dr. Agneta Fransson (NPI) Dr. Mario Hoppema (AWI)

2 9.3 GtC/yr % 2.1±0.9 Gt C/yr 2.6±0.5 Gt C/yr 4.5±0.9 Gt C/yr atm ocean land Previously ocean CO 2 uptake fossil fuel and cement about 48%, total ~30% ( , Sabine et al 2004); 50% ends up in surface ocean Current ocean anthropohenic CO 2 uptake about 25% changed ocean chemistry decreased ph ocean acidification The land C sink is determined as the residual between ocean and atm important to determine the ocean sink

3 The Southern Hemisphere oceans, south of 14 S to Antarctica, is the largest CO 2 sink taking up about 1.1GtC/y 40% of total anthropogenic CO 2 uptake Role of Southern Ocean for GCB: Climatology Major sink area is the Circumpolar Sink Zone (CSZ) S S of CSZ small sink or source ocean sink ocean source CSZ 2 mill observations Takahashi et al., 2009

4 Processes favouring ocean CO 2 uptake Cooling of warm water Wind and waves ACC connects and exchanges Deep water formation Biological CO 2 uptake in fronts, marginal ice zone, ice edge Sea-ice processes Glacial meltwater increase uptake potential - -

5 Global ocean CO 2 observing network (surface ocean CO 2 data) Volunteer-Observing-Ships (VOS) ~3 mill. surface water pco 2 measurements (Bakker et al. 2014:2016) Sampling bias between hemispheres: Largest part in Northern Hemisphere Increase pco 2 in surface water: average +1.5 µatm/yr: increased ocean acidification seasonal variation ~ µatm (Takahashi et al., 2009)

6 Atlantic SO: Surface pco 2 measurements Chierici, Fransson et al., 2004 Atlantic sector summer data is generally undersaturated relative to the atmospheric concentration of 400 µatm, likely an ocean CO 2 sink. Pretorius et al., 2014

7 Southern Polar Ocean: large unknowns South of 60 S small CO 2 sink or source region Insufficient seasonal resolution, large data gaps especially in sea-ice covered area Interannual variability data even more insufficient Frontal zones not reproduced well. Here large biological uptake but also upwelling Chierici et al., 2012

8 Water column changes: Atlantic sector- station locations repeat transect

9 Time trends (µmol kg -1 decade -1 ) and changes in oxygen, nutrients and total CO 2 of 4 water masses on the Prime Meridian in the Weddell Gyre TCO 2 Dissolved oxygen Silicate Surface water Warm Deep Water Weddell Sea Deep Water Period: Largest CO 2 increase in surface water and bottom water But also O 2 +Si decrease in bottom water Uptake of anthropogenic CO 2 in surface, but also non-steady state in circulation, ventilation change Weddell Sea Bottom Water Courtesy: M. Hoppema, AWI

10 Atlantic sector- station locations water column: repeat transect

11 Significant nutrient trends on the Weddell section: 1996 to 2011 Nutrient increases due to enhanced upwelling, likely caused by change in winds/sam ΔPO4/dt ΔSi/dt ΔNO3/dt Other possible explanation change in biological carbon pump Hoppema et al Mar Chem

12 SAM: Coupling between ocean and atmospheric system Positive phase SAM Stronger westerly winds More upwelling of CO 2 -rich deep water (CDW) SAM affects sea ice cover variability SAM = Southern Annular Mode Peninsula Amundsen Bellinghausen Warmer Less ice CO 2 - nutrient rich Weddell Sea Ross Sea Colder More ice Stammerjohn et al., 2008

13 SAM and upwelling and CO : CO 2 sink reduced due to increased westerly winds brought up high CO 2 water to surface, reducing the CO 2 uptake by 30% (Le Quéré et al., Science 2007, Lovenduski et al., 2008, OC+BGC model simulations) Confirmed by observations that CO 2 sink decreased in s, perhaps started to increase in 2000s (Takahashi et al., 2009) More observational evidence! 30 years of 2.6 mill observations (ocean, atm and rse) shows that the trend reversed in 2000 s the CO 2 sink in SO is now increasing again (2012 restored rate). Due to cooling (Pacific sector) and in Atlantic sector change in ocean circulation reduced upwelling (Landschützer et al., Science 2015) Observations show that the SO CO 2 sink fluctuates more than previously thought (Landshutzer et al., 2015) and models do not capture this variability (Lenton et al., 2013). Mean CO 2 uptake agrees, not timing resolve seasonal variability

14 BUT intraseasonality variability matters! Monteiro et al., 2015 found that it is not sufficient to resolve seasonal cycle and show that storm-linked intraseasonal variability in spring-summer need sampling intervals on a daily basis! Red areas reproducible seasonal variability high correlation Blue areas large interannual variability low correlation needs more sampling Ice edge Monteiro et al., 2015

15 SWE-SA expedition 1997/1998 Atlantic SO study SA Agulhas (SWEDARP) Fransson et al., 2004 measured diurnal variability in the chemical and physical environment and concluded that areas with strong diurnal cycles in temperature, wind and biological productivity, mixing of water require several measurements/day. The APF max to min CO 2 flux varied by a factor of 40 Support drifting buoys with sensors to resolve the role of this short term variability on the CO 2 flux and future CO 2 sink. APF WIE SIE SA Agulhas Fransson, Chierici et al., 2004 DSRII

16 Way forward: Interdisciplinary research required CC-Carbon links Ocean physics (upwelling, eddies, deep) Atmospheric science (wind, SAM ) Ocean biogeochemistry particularly CO 2, micro- and macro nutrients, oxygen Time series surface pco 2 water to assess trends Water column data understand cause of trends and changes in BGC processes Sea ice processes role of CO 2 sequestering and brine pump Biological productivity and carbon export Models (ocean-ice-bgc): High resolution models (resolve upper ocean features)

17 Southern Ocean Carbon & Climate Observatory SOCCO project captures the processes that need to be resolved and scale issues Fig.1: Depicts the SOCCO scale-centred approach which hypothesises that in order to understand and predict the century scale evolution CO2 and its radiative and ocean acidification forcing it is necessary to understand and correctly parametrize the processes inside the seasonal sub-seasonal and meso and sub-mesoscale window. This scale sensitivity links to the CO2 through the feedback of the upwelling of CO2 rich water, the biological pump and the solubility pump. Courtesy: SOCCO project:

18 18 Gliders, Robotics, Sensors, Buoys, Moorings High-resolution variability Meso-and submeso scale features Surface ocean dynamics BGC Sensors: ph, pco 2, O 2, nutrients Precision and accuracy ph: 0.02; pco 2 ±15 µatm wished ±0.005 and ±1 µatm, biofouling, speed and depth limitation

19 19 Research cruises for process studies, accumulation and trend studies in different water masses Process understanding and regional knowledge need shipbased surveys with sampling and high quality measurements in full water column and for calibration/validation of sensor and remotely sensed data

20 Drifting, seasonal observatories in the sea ice: the large unknown Multidisciplinary 6-month study Jan to June 2015 Granskog et al., 2016 Fransson, Chierici et al., 2017

21 New seasonal study in pack-ice in the Arctic Ocean reveal high winter CO 2 flux due to storms and leads Storm events promote air-sea CO 2 exhange in winter Sea-ice formation sustain winter time undersaturation Likely the case in Southern Polar Ocean too Surface water pco2 (µatm) Fransson, Chierici et al., 2017

22 Take a look at space: REmote Sensing of Carbon UptakE Produce CO 2 algorithms from ship- and satellite data Q u i c k T i me an d a T IF F ( U nc o mpr es se d ) de c omp re s so r ar e ne e de d to s e e th is pi ct ur e. Calculated surface water pco2 Multiregression Algorithm development fco 2 = f(sst, color, MLD) pco2 2 maps Shipboard sampling pco 2, SST, SSS, chl + Regional satellite SST & color data Apply algorithm to regional SST& color fields to obtain seasonal pco 2 maps Flux = k s ² pco 2 Flux maps Remote sensing SST, color & wind Wind data Algorithm development Gas transfer, k = f (U 10,SST) Chierici et al., 2009;2012 Chierici, Fransson et al., 2012

23 Observations, observations, observations No substitute exists for adequate observations. [... ] Models will evolve and improve, but, without data, will be untestable, and observations not taken today are lost forever. [... ] Today s climate models will likely prove of little interest in 100 years. But adequately sampled, carefully calibrated, quality controlled, and archived data for key elements of the climate system will be useful indefinitely. Carl Wunsch et al., 2013

24 Enkosi Ngiyabonga Takk! Dankie Thank You! Photo: Daniel Barrdahl Oden Southern Ocean expedition 2007/2008