carbon exchange dynamics in coastal and marine ecosystems · 2019-06-10 · 3 t 201213 • there...

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Carbon DynamicsT. Papakyriakou

ArcticNet Annual Research Compendium (2012-13)

Carbon Exchange Dynamics in Coastal and Marine Ecosystems

Project LeaderPapakyriakou, Tim (University of Manitoba)

Network InvestigatorsHelmuth Thomas (Dalhousie University); Lisa Miller (Fisheries and Oceans Canada - Institute of Ocean Sciences); Maurice Levasseur (Québec-Océan); Nadja Steiner, Svein Vagle (University of Victoria)

CollaboratorsSonia Michaud, Michael Scarratt (Fisheries and Oceans Canada - Maurice Lamontagne Institute); Yves Gratton (Institut national de la recherche scientifique - Eau, Terre et Environnement); Celine Gueguen (Trent University); Michel Gosselin, CJ (Christopher John) Mundy, (Université du Québec à Rimouski); Jean-Eric Tremblay (Université Laval); David G. Barber, Mats Granskog, Greg McCullough, Soren Rysgaard, Feiyue Wang, Emmelia Wiley (University of Manitoba); Ken Denman (University of Victoria)

Postdoctoral FellowsNicolas Geilfus (University of Manitoba); Daniel Godlovitch (University of Victoria)

PhD StudentsVirginie Galindo (Université Laval); Kristina Brown (University of British Columbia); Gauthier Carnat, Brent Else (University of Manitoba)

MSc StudentsChris Stammers, Rui Zhang (Centre for Earth Observation Science (CEOS); Meredith Pind (University of Manitoba)

Undergraduate StudentsJuris Almonte, Kristy Hugill (Centre for Earth Observation Science (CEOS); Leah Pengelly (Dalhousie University)

Technical StaffPatrick Sheldon (Centre for Earth Observation Science (CEOS)); Marty Davelaar, Kyle Simpson (Fisheries and Oceans Canada - Institute of Ocean Sciences); Martine Lizotte (Université Laval); Bruce Johnson, Marcos Lemes (University of Manitoba)

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Abstract

Our overarching objective is to understand the effects of climate change on the air-sea exchange and associated exchange budgets of climate active gases (carbon dioxide-CO2, dimethylsulfide-DMS, and nitrous oxide-N2O) in the Canadian coastal Arctic environment.

Oceans exert considerable influence on climate through their role on the global cycling of climatic active gases. For example, the world’s oceans are nature’s largest sink for CO2 and they globally account for a significant proportion of the natural emissions of the greenhouse gas nitrous oxide (N2O), and the vast majority of dimethyl sulfide (DMS) production. DMS is the largest source of sulfate in the marine environment, and once in the atmosphere the compound can trigger the formation of aerosols that serve as cloud condensation nuclei. While greenhouse gases (CO2 and N2O) act to warm the atmosphere, the increased production of DMS may have a cooling effect on climate by increasing back-scattered solar radiation. Our understanding of the effect that a changing Arctic climate and sea ice regime will have on the air-sea (and sea ice) exchange of these trace gases is currently somewhere between partially understood and mostly unknown, and hence important feedbacks that involve sea ice and the cycles of climate-active gases are currently not represented in general circulation models.

A requirement of this project is to parameterize those processes affecting the distribution of dissolved CO2, N2O, and DMS in surface waters of the Arctic, and their exchange with the atmosphere. Newly developed parameterizations are being implemented into a coupled atmosphere-sea ice-ocean biogeochemistry models to learn how the ocean’s response (physical, biogeochemical and biological) to climate change and variability will affect the atmosphere-ocean cycling of these climate active gases within the Arctic, and in turn

how these regional processes may affect the global budgets of these gases.

Key Messages

• The Cape Bathurst polynya region is a strong atmospheric CO2 sink, taking in CO2 at a mean rate of -10.1 ±6.5 mmol m2 d-1.

• The magnitude of the sink is influenced by ice and wind conditions.

• More than 50 % of this total uptake occurred through lead and polynya opening during the winter season.

• Wintertime CO2 uptake by polynyas at the circumpolar scale may be significant, on the order of 1012 g C yr-1.

• The southeastern Canada Basin has a weak capacity to absorb atmospheric CO2 during the ice-free season.

• The shallow mixed layer in the Canada Basin warms rapidly after ice retreat, raising the partial pressure of CO2 in the surface seawater (pCO2sw), which inhibits CO2 uptake.

• It is doubtful that ice-free summers in the Canada Basin will result in a significant new atmospheric CO2 sink.

• The density of the polar mixed layer (PML) of the southeastern Beaufort Sea increased through the winter due to cooling and brine rejection.

• The winter PML of the southeastern Beaufort Sea reached a maximum depth of 70 m in late April.

• The upper halocline water in the southeastern Beaufort Sea was usually located between 120 and 180 m depth, but could contribute to the SML during wind-driven upwelling events, in summer and autumn, and in brine-driven eddies, in winter.

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• There exists a strong link between brine dynamics and ice-ocean exchanges of biogeochemical compounds.

• Gas escape from sea ice will likely not occur unless the brine volume proportion in sea ice is greater than 7.5 %.

• Significant changes in bulk sea ice and brine carbonate system parameters were observed to be associated with increasing sea ice temperatures and high bottom ice Cla, despite little change in the water column properties.

• Recent fieldwork near to Resolute has determined the presence of a large pool of dissolved dimethylsulfoniopropionate (DMSP) and dimethyl sulphide (DMS) at the bottom of springtime sea ice with rapid (minutes) turn-over time.

• Melt ponds are characterized by low, but consistent concentrations of DMS, representing an atmospheric DMS source.

• In the highly stratified waters of Hudson Bay, late summer pCO2 ‘surface’ samples collected by hand from a small boat are almost always significantly different from those collected by rosette from the ship.

• At least in stratified coastal waters in the Arctic Ocean, water sampling from a large ship can substantially misrepresent the air-sea CO2 flux.

Objectives

Our over-all objective remains unchanged, that is to understand the effects of climate change on the air-sea exchange and associated exchange budgets of climatically relevant gases (carbon dioxide-CO2, dimethylsulfide-DMS, and nitrous oxide-N2O) in the Canadian coastal Arctic environment.

Sub-objectives include:

• To monitor spatial and temporal changes in both the dissolved concentrations of CO2, DMS, and

N2O within the surface water and sea ice and their exchange with the atmosphere;

• To improve our understanding of the key mechanisms responsible for the production, distribution and exchange of relevant gases within the water column and sea ice, and across the water/ice/air interfaces;

• To quantify the contemporary atmospheric CO2 source/sink status of peripheral seas within the ArcticNet domain;

• To develop parameterizations for air-sea (sea ice) gas exchange;

• To implement parameterizations into a sea ice and ocean biogeochemical models, and models for the remote detection of dissolved gas concentrations and exchanges using satellite observations.

Introduction

The recent reduction in sea ice concentration has exposed large areas of Arctic Ocean to the atmosphere for increasingly long periods of time, and substantially increased the area undergoing annual sea ice formation and thaw. Observations have shown that the surface water in many Arctic shelves have low concentrations of dissolved CO2 during the open water season (Else et al., 2012a; Shadwick et al., 2011), and as a consequence, a first order response to reduced ice coverage would be enhanced uptake of atmospheric CO2 (Bates and Mathis, 2009). The biological uptake of dissolved CO2 may be enhanced owing to increased availability of light in the surface mixed layer (Arrigo et al., 2008). In many parts of the Arctic however, primary production may be nutrient limited (Cai et al., 2010; Jutterström and Anderson, 2010), and upwelling, which could otherwise alleviate nutrient limitations (e.g., Tremblay et al. 2011), may also introduce dissolved inorganic carbon from the upper halocline, raising the partical pressure of CO2 (pCO2) in the surface mixed layer with consequences on the region’s uptake potential (e.g., Else et al. 2012a; Mathis et al. 2012; Mucci et al. 2010). Uptake will be further

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limited through the warming of the shallow ice-free mixed layer (Else et al., 2012a; Cai et al., 2010).

During the cold season, vertical brine transport in sea ice has strong control on how mass and energy is exchanged between the atmosphere, sea ice and ocean (e.g., Steele and Morison, 1995; Orsi et al. 2009; Shcherbina et al. 2003, Tamara et al. 2008). As brine percolates through the ice matrix, it can also transport other dissolved and particulate constituents with it, likely influencing biogeochemical processes and elemental cycling across the ocean-sea ice and likely atmosphere interfaces. Young thermodynamically and geochemically active sea ice will quite likely enhance CO2 uptake through the sea ice carbon pump (transport of DIC-rich brine to depth with ice growth, with residual ice melt being low in DIC and high in total alkalinity, e.g., Rysgaard et al. 2007), meaning the wide-scale transition from multi-year ice to seasonal sea ice may peak CO2 uptake during initial ice formation, and repeated episodes of ice formation. The latter is characteristic of polynya environments. Uncertainty surrounding the net affect of warm- and cold-season processes on annual totals of air-sea CO2 exchange in the Arctic Ocean has continued to motivate our research this past year.

Little is known of the production and emission of other climatically active gases in the Arctic Ocean, including dimethylsulphide (DMS), and the powerful greenhouse gas nitrous oxide (N2O). The role of sea ice in the cycling of these gases is too poorly understood to predict the effect of the Arctic’s changing ice regime on annual budgets (Elliot et al., 2012). Recent results by our group have shown relatively high concentrations of DMS in the Beaufort Sea, across the Canadian Archipelago, and the northern part of Baffin Bay in the fall, with maximum concentrations and microbial production rates measured in Lancaster Sound (Luce et al., 2011, Motard-Côté et al., 2011). Results from the aerosol and sulfur dioxide measurements made during the ArcticNet/Arctic SOLAS cruises (using isotope apportionment) suggests that the amount of SO2 produced from DMS oxidation under clean air conditions was sufficient

to cause aerosol nucleation (Rempillo et al., 2011). A second atmospheric team showed that high DMS emissions could result in aerosol nucleation events (Chang et al., 2011), providing positive evidence that sea-air ventilation and atmospheric oxidation of DMS in the Arctic results in new particle formation: a process that is disputed in the recent literature. These results confirm the importance of DMS emissions from the Arctic Ocean as a source of aerosols in the arctic and underline their importance for climate. During the project, we also conducted the first measurements of N2O in the sea ice (Randall et al., 2012). These measurements show that the ice was always under-saturated in N2O as compared to the atmosphere and the under-ice water. These observations suggest that sea ice could represent a source of N2O for the atmosphere in fall during ice formation, and a sink during the ice melting period in spring, although numerous uncertainties remain on many aspects affecting production and emission in ice-dominated environments.

Activities

Time frame and study area:

Despite the loss of the CCGS Amundsen to science this year, 2012 was extremely busy for project personnel.

1. Three team members were onboard the CCGS Radisson for a short expedition in Hudson Bay. The project objectives were to examine how fresh water (ice melt and river water) influence surface water pCO2. The monitoring program consisted of basic ship- and boat (zodiac and barge) based sampling of water to determine carbonate chemistry, and oxygen-18 isotopic ratio. The dissolved CO2 concentration in water was measured using a portable automated flow through water CO2 monitoring system. Cruise participants included L. Miller, T. Papakyriakou, and K. Hugill (UofM).

2. Three team members participated in the

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Arctic-ICE springtime sea ice study on Allen Bay (northwest of Resolute Bay: 74°43N; 95°09W) from May 21 to June 21. The ice camp study provides a unique opportunity for multidisciplinary study into sea ice and upper ocean biology, biogeochemisty and geophysics over the spring to summer transition. The team focused on three aspects of sea ice and under-ice seawater: 1) inorganic carbon system; 2) the production and distribution of DMS, and 3) N2O. The inorganic carbon program was designed to monitor seasonal changes in the sea ice inventory of inorganic carbon in relation to carbon flows across the air-ice-ocean interface. Other objectives were to assess the microbial turnover rate of the large pool of dissolved DMSP found at the bottom of the sea ice during the two previous sampling years, to quantify DMS in the brines, and to explore the potential importance of melt pounds as DMS source for the atmosphere. N2O measurements were also conducted in the brines, the bottom of the ice, and in the water column.

3. Two team members (T. Papakyriakou and B. Johnston) participated in a winter sea ice project in Young Sound, Greenland over the period between March 13 and 30, 2012. The objective of this case study was to constrain the wintertime carbon budget of a landfast ice system, through the measurement of major horizontal and vertical carbon flows, and evaluation of the time dependent change in carbon store of the sea ice and underlying water column. Team objectives were to explore the relationship between the air-sea ice CO2 and environmental variables, including ice thickness, snow cover, and thermodynamics. Research was conducted in collaboration with, and sponsored by the University of Manitoba CERC program, and the Greenland Climate Centre.

4. Team members (T. Papakyriakou, B. Johnston and N. Geilfus) participated in the inaugural 2012, and subsequent 2013 winter sea ice

experiments at the Sea Ice Experimental Research Facility (SERF) at the University of Manitoba. Objectives were to quantify the inorganic carbon flows and budget associated in a closed sea ice / water column system.

In addition to field activities, we analyzed data from previous ship- and ice-camp experiments, and collectively the analysis has resulted in numerous papers and presentations. Results are forwarding our ocean and ice biogeochemical modelling initiative.

Results

Many results published in 2012 stem from (but not limited to) observations that were made during the 2007-08 ArcticNet/IPY-CFL/Arctic-SOLAS, and 2009 cruises of the CCGS Amundsen. The IPY and ArcticNet expeditions provided an opportunity for near year-round observations of the sea ice and ocean biogeochemical system, and the associated air-sea exchanges of relevant gases. Results are presented in the areas of (1) Sea Ice CO2 System and Fluxes, (2) The CO2 System of the Upper Water Column, (3) Surface Seawater pCO2 and Regional Carbon Budgets, (4) Non-Carbon Biogenic Gas Production and Emission Characteristics, and (5) Biogeochemical Modelling.

(1) Sea Ice CO2 System and Fluxes

In previous compendiums we reported that:

• the partial pressure of CO2 (pCO2) in sea ice was observed to be highly variable over the life cycle of seasonal sea ice, being generally much higher than atmospheric levels during the cold seasons of the fall, winter and early spring and was generally less than atmospheric levels in the late spring and summer, when it was warmer (Geilfus et al. 2012b);

• air-sea ice CO2 exchange (Geilfus et al., 2012a) appeared to be largely controlled by ice

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temperature, presumably through its control on the brine pCO2 and sea ice permeability;

• the total carbon content of the ice increased throughout the winter season, primarily because of the increasing ice thickness, while the average carbon concentration decreased due to brine drainage and CO2 outgassing to the atmosphere;

• in many cases, observed sea ice carbonate chemistry provides indirect evidence for the sea ice carbon pump as proposed by Rysgaard et al. (2007);

• both dissolved inorganic carbon (DIC) and pCO2 in the sea ice decreased in concentration with the progression from winter to spring, a likely consequence desalination (Geilfus et al. 2012).

New results have forwarded our understanding of the system by confirming, for the first time, direct evidence for the existence of CaCO3 minerals (as ikaite) in frost flowers over Arctic landfast sea ice, and forwarded our understanding on air-sea biogeochemical coupling in the presence of sea ice.

Gelfus et al., (2013) confirmed the precipitation of ikaite in frost flowers of 1-week old landfast sea ice near to Barrow, Alaska using Raman spectroscopy and X-ray analysis. The precipitation of the mineral depleted the surface sea ice by 2069 µmol kg-1, which would have resulted in an ice to air CO2 flux between 20 mmol m2 d-1 and 40 mmol m2 d-1, consistent with chamber flux measurements.

Zhou et al. (2013) examined the link between brine drainage and sea ice biogeochemistry on landfast sea ice near to Barrow Alaska. Three stages of brine dynamics were observed over the annual cycle: (1) sea ice bottom layer convection, (2) full-depth convection and (3) brine stratification. Full depth convection favoured the exchange of biogeochemical compounds (nutrients and stable isotopes, including δD and δ18O) between the sea ice and seawater, while brine stratification limited these exchanges. Similar results

were reported by Carnat et al. (2013) for drift ice characteristic of polynya environments. Interestingly, Zhou et al. observed that argon responded differently to brine dynamics than the other biogeochemical compounds. The anomaly was attributed to the tendency for argon to nucleate into gas bubbles. The data has allowed us to establish (for the first time) a critical sea ice brine volume threshold, above which gas bubbles in sea ice will escape from the sea ice to atmosphere. The threshold is a brine volume fraction of approximately 7.5 %. This brine volume threshold is slightly higher than that required for free brine drainage (5 %). That is, while gases dissolved in brine are fully mobile beyond a brine volume fraction threshold of 5 %, and brine volume fraction above 7.5 % for gas to escape. The study therefore shows that gases can accumulate in sea ice and persist longer than what would be expected based on brine migration.

(2) The CO2 System of the Upper Water Column

In previous compendiums we reported that sea ice formation and melt affects the under-ice profiles of temperature, salinity, DIC, and Ωar, the saturation state for aragonite (Chierici et al. 2011; Shadwick et al. 2011) based on data collected during the 2007-08 IPY/ArcticNet cruises of the CCGS Amundsen. Lansard et al., (2012) recently extended the research by examining the seasonal variability of water mass distributions in the southeastern Beaufort Sea using data originally collected during the 2003-04 CASES project. They found the autumn mixed layer (SML, generally S < 30) had an average seawater fugacity of CO2 (fCO2-sw) of 292 ± 27 µatm, and therefore was undersaturated with respect to the average atmospheric fCO2 value. Over the winter, the average fCO2-sw increased to 370 ± 33 µatm in the mixed layer as a result of brine rejection, bacterial respiration and possibly air-sea CO2 exchange in the Cape Bathurst Polynya (Else et al., 2011). In summer the salinity of the SML decreased to below 29 and surface temperature increased up to +7 °C in response to long daylight hours and the loss of ice cover. Very low-salinity surface water (< 10) with

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high fCO2-sw (> 500 µatm) was observed at the Mackenzie River mouth. Conversely, relatively low sea surface salinities (< 30) with very low fCO2-sw (< 300 µatm) were observed beyond the shelf break and close to the ice pack. The density of the Polar Mixed Layer (PML) increased through the winter due to cooling and brine rejection. The winter PML reached a maximum depth of 70 m in late April. The Upper Halocline Water (UHW fCO2-SW > 600 μatm) was usually located between 120 and 180 m depth, but could contribute to the SML during wind-driven upwelling events, in summer and autumn, and during brine-driven eddies, in winter. An example of the water mass distibution along the Kugmalitt canyon is shown in Figure 1 for the autumn of 2003.

(3) Surface Seawater pCO2 and Regional Carbon Budgets

Research has built on the results of Else et al. (2011; 2012a) and Shadwick et al. (2011) in which we have previously reported that:

• the partial pressure of CO2 at the water surface (pCO2sw) in Amundsen Gulf remained undersaturated relative to atmospheric levels over much of the annual cycle;

• enhanced air-sea CO2 exchange relative to open water rates of exchange (i.e., 10 to 100 times higher) was observed in areas of mobile and broken sea ice in the winter season;

Figure 1. Example of water mass distribution ( %) along Kugmalitt canyon in autumn 2003. The water masses are: Mackenzie water (MW), sea ice melt (SIM), winter polar mixed layer (PML), upper halocline water (UHW), and Atlantic water (ATW).

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• many factors contribued to affect pCO2sw, and the relationships were observed to be complex having both spatial and temporal components;

• the annual cycle of pCO2sw is strongly affected by location, varing among three regions of the

southeastern Beaufort Sea (Amundsen Gulf, Banks Island Shelf and Mackenzie Shelf) reported by Else et al. (2012);

• none of the regions precisely following the conceptual model of the annual pCO2sw cycles for other Arctic polynyas (North Water and Northeast Water, Yager et al. 1995);

• Amundsen Gulf constituted a net annual (2007-08) carbon sink.

Else et al. (2012b) reported that despite the occasional introduction of water with high dissolved inorganic carbon (DIC) from the upper halocline (UHW) into the surface mixed layer (SML) associated with ice edge upwelling (see for example Figure 2), the landfast ice system in Amundsen Gulf remained a sink for atmospheric CO2 over the 2007-08 International Polar

Figure 2. Measure pCO2sw during transects conducted in October-November, 2007 (Else et al., 2012b). Transects are overlain on RADARSAT-1 SAR imagery. The dashed line denotes the landfast ice edge.

Figure 3. Measured pCO2sw during transected conducted in June 2008. Transects are overlain on true-colour MODIS imagery.

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Year. In this area upwelling occurs largely in the spring and fall, and is driven by strong and persistent easterly winds. High ice concentration during these events prevented significant outgassing. In the late spring and early summer primary production and ice melt combined to lower pCO2sw, allowing significant CO2 uptake (see for example Figure 3). Because wind direction is instrumental in promoting upwelling at the ice edge, the annual exchange budget will be prone to significant inter-annual variation given the effect of vertical mixing on pCO2sw.

Else et al. (2013a) showed that the Cape Bathurst polynya region was a net annual sink for atmospheric CO2. In their estimate they consider enhanced flux through leads and other small openings in the sea ice during the cold season (Figure 4). The high flux estimates in the fall (Figure 4) were the results of the large amounts of open water as the ice began to form while ΔpCO2 was strongly negative. The spring uptake pulse corresponds to the spring season opening of the polynya (high primary productivity, open water and conditions conducive to new ice formation). The mean uptake over the freezing period (182 days) was estimated to be -15 ±10.0 mmol m2 d-1. The total annual average flux (10.1 ±6.5 mmol m2 d-1) represents the combination of freezing and non-freezing fluxes for the Cape Bathurst polynya region over the 2007-2008 International Polar Year (IPY). This estimate is approximately 3x higher than the preliminary estimate of Shadwick et al. (2011). The results add to the increasing body of literature showing that most Arctic shelf seas act

Figure 4. Calculated CO2 flux for open water using the traditional bulk parameterization with ice concentration correction (black line), and estimates considering the results of Else et al., (2011) (red line) for the Cape Bathurst Polynya region (Else et al, 2013a).

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Figure 5: Underway surface water measurements of (a) observed pCO2sw, (b) salinity and (c) sea surface temperature, overlain on a composite of RADARSAT-1 images, collected during the 2007-08 IPY.

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as sinks for atmospheric CO2. Several factors contributed toward making this polynya a strong CO2 sink. A main feature is the enhanced wintertime uptake of CO2 by the surface ocean in areas of broken and mobile ice cover and persistently negative ΔpCO2 (seawater pCO2 less than atmospheric levels). A sensitivity analysis revealed that both high wind and low ice coverage supported the high rates of CO2 uptake observed during the 2007-08 IPY.

Else et al. (2013b) provided the first-ever assessment of CO2 uptake in the southeastern Canada Basin during the ice-free season using data collected during the 2009 cruise of the CCGS Amundsen (Figure 5) and a model that calculates changes to the surface water CO2 system parameters over a 100-day ice-free period based on observed heating and cooling rates, and calculated air-sea exchange. The over-all mean uptake of -2.4 mmol m2 d-1 reported in the study (Figure 6) is ~ 60 % lower than the mean uptake rate estimated by Cai et al. (2010) over a similar 100-day period in the southwestern Canada Basin.

Preliminary results from this summer’s cruise in Hudson Bay indicate that in the highly stratified waters of Hudson Bay, late summer pCO2 ‘surface’ samples collected by hand from a small boat are almost always significantly different from those collected by rosette from the ship. The pCO2 values determined from the small boat were usually lower, implying a small drawdown of atmospheric CO2, as opposed to outgassing implied by the rosette samples. However, in particularly high- pCO2 waters, the small-boat samples had higher values, indicating greater outgassing than implied by the rosette samples. These results show that at least in stratified coastal waters in the Arctic Ocean, water sampling from a large ship can substantially misrepresent the air-sea CO2 flux.

(4) Non-Carbon Biogenic Gas Production and Emission Characteristics

In previous compendiums we reported:

• the first concentration measurements of N2O in the sea ice (Randall et al., 2012);

• high concentration of DMSP (dimethylsulfoniopropionate, a precursor to the climatically active gas dimethyl sulphate – DMS) at the sea ice base in the late spring and early summer; decreasing thereafter;

• that a relationship between Cla, and the abundance of DMSP appears related to light availability, although the nature of the relations remains unclear.

High concentrations of dimethylsulfoniopropionate (DMSP), the algal precursor of DMS, were measured in the lower centimeters of springtime sea ice, both in

STN. L1, FCO2 = -2.4

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SST 0.09oC d-1, FCO2=-3.0

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Figure 6. Results based on a model for a 100 day air-sea gas exchange during ice-free conditions in the SE Canada Basin: (a) pCO2sw evolution during model runs, with the horizontal line denoting atmospheric pCO2; (b) air-sea CO2 flux evolution for model runs at each station; (c) air-sea CO2 flux evolution during the sensitivity runs. Refer to Else et al., (2013b) for details.

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the particulate and dissolved phase during the 2012 springtime ArcticIce experiment near to Resolute Bay (74°43N; 95°33W), Nu. Concentrations of DMS as high as 700 nmol l-1 were also measured at the bottom of the ice. As observed in past work, very little of the dissolved DMSP was found in the water column at the onset of sea ice melt. Microbial rate measurements, using radiotracers, showed that the under-ice bacterial community had a high affinity for DMSPd (turnover time of the DMSPd pool of ca. 0.4 d), but exhibited no response to the release of DMSP from the ice (Figure 7).

Very fast turnover rates of the DMSPd (minutes) were also measured in the sea ice. These turnover rates support the current hypothesis that sea ice brines host active microbial communities during the spring season. In contrast, samples from melt pounds revealed low concentrations of DMSP and potentially DMS.

(5) Biogeochemical Modelling

The integration of a sea ice and biology (carbon) module in the General Ocean Turbulence Model (GOTM) has continued. GOTM is a vertical column model of ocean physics, with an emphasis on turbulent mixing processes. It tracks temperature, salinity and velocities in a water column of adjustable depth, with a variable number of layers.

Ice Module

The ice module is adapted from a single-thickness thermodynamic model developed by Flato and Brown (1996). A large number of small improvements and bug-fixes have been effected in the new salinity and heat flux routines (Vancoppennolle, 2008; McPhee, 2008) within the sea ice routine. In addition, a prognostic area fraction variable has been added based on (Hibler, 1979). The area fraction module models the amount of open water present in the area of study, and has been implemented in order to study the relationship between the amount of open water in an ice-covered region and the gas fluxes between ocean and atmosphere. Work has also progressed on model parameterisations of light penetration and attenuation in the GOTM sea-ice module to improve the representation of sub-ice and within-ice photosynthetic active radiation (PAR). This will improve the representation of light availability for sea-ice and pelagic ecosystems. In its present state, the sea ice routine is totally integrated with the GOTM 4.x model, and now offers a choice of schemes to calculate the salinity profile, and heat profiles.

Carbon Module

The carbon module is an adaptation of a model developed by Steiner and Denman (2008). It simulates an ecosystem consisting of two classes of phytoplankton (large and small) and two classes of zooplankton (large and small), detritus, NH4 NO3, silica, particulate silica, and particulate inorganic carbon. From the population dynamics, dissolved inorganic carbon, alkalinity, di-methylsulfide (DMS and DMSpd), O2, and N2 levels are calcuated. In its original form, the large zooplankton population (Zo2 ) is prescribed. This model has been modified to allow prognostic Zo2 . As with all biological models, the system must be closed by specifying a mortality rate for species that are not preyed upon. The large zooplankton are the only such species in this model, and a linear (mortality of large zooplankton is proportional to the population) or quadratic (mortality is a quadratic term, dependent on the population) term

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Figure 7. DMSPd microbial loss rate constant measured under the ice during the ice algal bloom in 2012.

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is possible. Current progress has been summarized in a model documentation, including a section on improvements. Apart from some janitorial work, issues and future work with respect to the stratification stability and the McPhee heat flux, the brine drainage parameterisation, the formulation of the ice areal fraction, the biology component and the coupling to the atmospheric interface are discussed in the expanded report.

Canadian Earth System Model

The evaluation of the Canadian Earth System Model in the Arctic has continued in collaboration with CCCma. Changes in carbonate chemistry and acidification under a changing climate have been evaluated using CanESM2 as well as 5 additional CMIP5 Earthsystem models. Steiner et al., (2013a), discusses a sensitivity study with CanESM2 showing that enhanced CO2 exchange in sea-ice areas in the Arctic Ocean increases the uptake in fall and winter, allowing more continuous equilibration and hence reduced uptake in summer. The reduction in summer also hints at a limited CO2-uptake capacity of Arctic surface waters. Steiner et al. 2013a point out that retreating sea-ice in the future leads to a similar shift in the seasonal cycle. The annual mean carbon uptake of the Arctic Ocean north of 68°N changes only slightly with the enhanced flux parameterisation (< 3 % ) (Figure 8). For the central Arctic (north of 80°N) the change is up to 21 % and accelerates ocean acidification, i.e. locally, surface waters could reach aragonite undersaturation 1-2 decades earlier. The differences between standard and enhanced exchange test runs become less pronounced in the future due to the reduced ice cover and extended open water season. For the Antarctic sea-ice zone where the CO2 flux is out of the ocean, the enhanced exchange increases outgassing, slightly slowing down acidification.

An intercomparison of CMIP5 models (Steiner et al. 2013b) show that future projections under Representative Concentration Pathways 4.5 and 8.5 consistently project a reduction in surface pH from

about 8.1 in the recent past to about 7.7 by the end of the century closely linked to a reduction in the saturation state of calcium carbonate minerals from about 1.2 (2.0) to about 0.6 (1.0) for aragonite in the Canada Basin. The publication points out that in a large part of the Arctic ocean basins, increased CO2 uptake and additional freshwater contributions at the surface allow the saturation state to approach undersaturation both from the top and the bottom, rendering the common definition of the saturation horizon unsuitable. It is highlighted that while the models differ in both resolution and landmask, affecting in-, out- and through flows in the Arctic, main differences between projected acidification in the models seem to be related to the reduction in sea-ice cover and respective responses in wind mixing and stratification.

Jan Mar May Jul Sep Nov Jan

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1996_2005 B0 ____ B10 -.-. B20 ---- B100 .....

(a) (c)

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Figure 8. Regionally integrated monthly climatologies of CO2 exchange (Tg C y-1) for standard and sensitivity runs. Positive values indicate outgassing. a) 1996-2005, b) 2041-2050 (black) and 2091-2100 (grey) for the area north of 68°N. c) 1996-2005, d) 2041-2050 (black) and 2091-2100 (grey) for the area north of 80°N. Shown are the standard runs (solid lines) and the three sensitivity studies reflecting aqn enhancement equivalent to 10 % (B10, dash-dot), 20 % (B20, dashed) and 100 % (B100, dotted) open water area, with the later representing a free exchange test run. B10 and B100 are omitted in b) adn d) to improve clarity.

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Discussion

(1) Sea Ice CO2 System and Fluxes

Common stages of brine dynamics were observed over the annual cycle for both landfast and drift ice (Zhou et al. 2013 and Carnat et al. 2013) suggesting that observations reported by the authors are widely applicable to the Arctic’s new sea ice regime. The liquid permeability of sea ice is well established - above 5 % porosity (or brine volume) brine is thought to freely drain (Golden et al. 2007). By comparison, there has been little consideration given to the process of gas permeation through sea ice. Our finding (Zhou et al. 2013) that gas bubbles in sea ice

will escape from the sea ice to atmosphere beyond a brine volume threshold of 7.5 % is critically important toward the understanding of air-sea gas exchange in the presence of sea ice, and constitutes a significant contribution to the community. Collectively the results provide us with a better understanding on seasonal limitations (or potential) for free or restricting coupling of gas and liquid transport across the the ocean-sea ice-atmosphere interface (Figure 9).

(2) The CO2 System of Regional Arctic Water’s and Carbon Budgets

The polynya and extended flaw-lead system of the southeastern Beaufort Sea appears to be a net sink for

Figure 9. Schematic representation of gas entrapment and the evolution in sea ice through the 3 stages of brine dynamics described above. Beyond a brine volume fraction of ~ 7.5 %, bubbles could migrate upward in permeable layers due to their buoyancy, while gas dissolved in brine would migrate with the brine (Zhou et al. 2013).

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atmospheric CO2 over an annual cycle, reinforcing the paradigm that Arctic polynyas are likely significant sinks for atmospheric CO2. It is important to note that estimated uptake during the cold season was far in excess of that observed over the non-freezing period (-~15 mmol m2 d-1 vs. ~-5 mmol m2 d-1). Since the freezing period (~184 days) was approximately equal to the length of the non-freezing period (182 days), the results highlight the importance of cold season gas exchange processes on annual totals, and how sensitive long-term budgets will be to changing climate and ice regimes (Else et al. 2013a).

Results from both the fastice (Else et al. 2012b) and polynya systems (Else et al. 2013a) show that the direction and magnitude of air-sea CO2 exchange to be highly dependent on wind, in addition to ice concentration. Because wind direction is instrumental in promoting upwelling at the ice edge, the annual exchange budget will be prone to significant inter-annual variation given the effect of vertical mixing on surface water pCO2 (Landsard et al., 2012). A sensitivity analysis (Else et al. 2013b) revealed that both high wind (anomalously windy) and low ice coverage (second lowest sea ice extent was recorded in Sept. 2008) supported the high rates of CO2 uptake observed during the 2007-08 IPY year over the extended Cape Bathurst Polynya. Both wind and sea ice concentration were affected by pressure patterns in the Beaufort Sea. One of the major causes of the anomalous basin-wide low ice conditions in 2007 and 2008 was the persistence of a strong “Arctic Dipole Anomoly”. Recent studies suggest that the Arctic Dipole pattern will become more common, and thus the mean annual CO2 flux estimated from the 2007-08 study may be representative of future air-sea exchange in the region (Else et al. 2013a).

The sign and magnitude of air-sea difference in pCO2 initiates CO2 uptake or evasion. Seasonal variations in pCO2sw appear to be consistent within the Cape Bathurst Polynya region (Figure 10), at least over the last decade. This region is but one of many coastal polynyas around the circumpolar Arctic. On extrapolating our results to coastal polynyas across the

we estimated wintertime uptake to be on the order of 1012 gC yr-1 in CO2 (Else et al. 2013b).

Our findings that the southeastern Canada Basin likely will not absorb significant amounts of atmospheric CO2 during an extended ice-free period (Else et al. 2013b) goes against the popular conjecture that sea ice loss over the Arctic Ocean would create a significant new summertime sink of atmospheric CO2. The combination of the rapid equilibration of CO2 between the shallow surface-mixed layer and atmosphere (Cai et al. 2010) rapid warming of the surface water that occurs when ice is removed were flagged as key factors that mitigate against pronounced CO2 uptake (Else et al. 2013b). It appears that nutrients limit primary production, capping primary production despite the increased availability of light that is associated with the reduction in sea ice cover. How the CO2 exchange budget for the Canada Basin in the Arctic will respond to future ice conditions will depend on numerous processes, including vertical mixing, sea ice carbon pump, and a freshening of the Canada Basin.

Figure 10. pCO2sw observations made in the Cape Bathurst polynya region during the CASES cruises of the CCGS Radisson and Amundsen (2003-04, Mucci et al., 2011), ArcticNet (2006 and 2009) cruises of the CCGS Amundsen, and 2007-08 CFL/ArcticNet Amundsen expedition (Else et al., 2012). Adapted from Else et al. (2013).

15



Conclusion

Over the past year we have made considerable progress in addressing project objectives.

Observations indicate that the Arctic Ocean is important in the production and cycling of the climate-active trace gases dimethylsulfide (DMS) and nitrous oxide (N2O), and that the production of these gases is likely affected by changes in the distribution of sea ice. Ice algae in particular is an important reservoir of dimethylsulfoniopropionate (DMSP), the non-volatile precursor of DMS). Unknowns relate to the production of DMSP, its biogenic conversion to DMS, and the ultimate fate of DMS. That is, what fraction of DMS produced is released to the atmosphere, and at what rate?

A key unknown in the role of sea ice on air-sea gas exchange relates to possible rates of gas transport in sea ice via diffusion and convection, in both dissolved and gaseous forms. Here we’ve made progress in so far as we now know gas bubbles may transport through sea ice, provided brine volume is sufficiently high (in excess of ~7.5 %). Much research is required to document gas transport rates and relationships to ice porosity and permeability.

Our synthesis of annual uptake of CO2 for the extended Cape Bathurst polynya region is based on arguably the most comprehensive CO2 system data set of any polar sea globally. Results show that the region is indeed a strong sink for atmospheric CO2, particularly during the winter season. Atmospheric forcing however influences uptake through its effect on wind and sea ice coverage. The potential for progressively more open water during the winter season in the Arctic is a distinct possibility and a significant challenge in predicting the effectiveness of wintertime CO2 uptake lies in our ability to understand those processes that underpin the exchange. This includes factors affecting pCO2sw, the hydrodynamics of the exchange, and vertical distribution of DIC. Also we need to increase our presence in other important polynya regions (e.g.,

North Water) to confirm the representativeness of results steming from research in the Cape Bathurst polynya.

Less is known on role of the changing sea ice on the annual CO2 exchange in the ocean’s deeper basins. Results thus far suggest that CO2 uptake by Canada Basin will not increase with increasing length in the ice free season. For now it appears that the shallow mixed layer is nutrient limited, preventing the system of realizing the potential for primary production afforded by the availability of light. Freshening of the Basin may strengthen the stratification. Nutrient replenishment through upwelling would enhance the biological draw down of CO2, but likely also introduce DIC-rich upper-haline water into the mixed layer. As wintertime uptake requires a negative air-sea gradient in pCO2, a significant unknown relates to the response of the sea ice carbon pump during the winter season to changing sea ice distribution.

Future work will target unknowns highlighted above.

Acknowledgements

Numerous individuals and agencies support this project, including students, and technical and administrative staffs at the University of Manitoba, Université Laval, Institute for Ocean Science (DFO), Québec-Océan, Dalhousie University and the University of British Colombia. Research would not be possible without the support of the Canadian Coast Guard, in particular the officers and crew of the CCGS Amundsen. PCSP provided logistical support for sea ice based research. Finally we are all grateful for the support extended by the ArcticNet staff. Funds for the research are provided by numerous sources, including: ArcticNET, NSERC Discovery and Northern Supplement Grant Programs, DFO, University of Manitoba CERC and CRC programs, University of Manitoba NSERC Bridge Fund, Greenland Climate Centre, and AANDC, through the Northern Studies Training Program.

16



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Else, B.G.T., R.J. Galley, T.N. Papakyriakou, L.A. Miller, A. Mucci, and D. Barber, 2012. Sea surface pCO2 cycles and CO2 fluxes at landfast sea ice edges in Amundsen Gulf, Canada, J. Geophys. Res., 117, C09010, doi:10.1029/2012JC007901.

Else, B.G.T., T.N. Papakyriakou, M.G. Asplin, D.G. Barber, R.J. Galley, L.A. Miller, and A. Mucci, 2013a. Annual Cycle of air-sea CO2 exchange in an Arctic polynya region. Glob. Biogeochem. Cycl., 2012GB004425, Manuscript Accepted.

Else et al. B.G.T., R.J. Galley, B. Lansard, D.G. Barber, K. Brown, L.A. Miller, A. Mucci, T.N. Papakyriakou, J.-É. Tremblay, S. Rysgaard, 2013b. Sea ice loss and the changing atmospheric CO2 uptake capacity of the Arctic Ocean: Insights from the southeastern Canada Basin. Geophys. Res. Lett., Manuscript accepted.

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Geilfus, N.-X., G. Carnat, T. Papakyriakou, J.-L. Tison, B. Else, H. Thomas, E. Shadwick, and B. Delille, 2011. pCO2 dynamics and related air-ice CO2 fluxes in the Arctic coastal zone (Amundsen Gulf, Beaufort Sea), ). J. Geophys. Res., 117, C00G10, doi:10.1029/2011JC007118.

Geilfus, N-X, G. Carnat, G. Dieckmann, N. Halden, G. Nehrke, T. Papakyriakou, J-L Tison, and B. Delille, 2013. First estimates of the contribution of CaCO3 precipitation to the release of CO2 to the atmosphere during young sea ice growth, J. Geophys. Res: Oceans, 20112JC007980R, Manuscript Accepted.

Golden, K.M., H. Eicken, A.L. Heaton, J. Miner, D.J. Pringle, and J. Zhu, 2007. Thermal evolution of permeability and microstructure in sea ice, Geophys.

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Lansard, B., A. Mucci, L.A. Miller, R.W. Macdonald, and Y. Gratton, 2012. Seasonal variability of water mass distribution in the southeastern Beaufort Sea determined by total alkalinity and δ18O, J. Geophys. Res. 117, C03003, doi:10.1029/2011JC007299.

Luce M, M. Levasseur, M. Scarratt, S. Michaud, R. Kiene, C. Lovejoy, M. Gosselin, M. Poulin, and Y. Gratton, 2011. Fall distribution and microbial metabolism of dimethylsulfoniopropionate and dimethylsulfide during the 2007 Arctic ice minimum, J. Geophys. Res. 116, C11, doi: 10.1029/2010JC006914.

Mathis J.T., et al., 2012. Storm-induced upwelling of high pCO2 waters onto the continental shelf of the western Arctic Ocean and implications for carbonate mineral saturation states, Geophys. Res. Lett., 39, L07606, doi:10.1029/2012GL051574.

McPhee, M. G. (2008). Air-ice-ocean interactions: turbulent ocean boundary layer processes. 215 pp. Springer.

Miller, L.A., G. Carnat, B.G.T. Else, N. Sutherland, and T. Papakyriakou (2011b), Carbonate system evolution at the Arctic Ocean surface during autumn freeze-up, J. Geophys. Res., 116, C00G04, doi:10.1029/2011JC007143.

Motard-Côté, J., M. Levasseur, C. Lovejoy, M. Scarratt, S. Michaud, M. Gosselin, Y. Gratton, and R. Kiene, 2011. Distribution and phylogenetic affiliation of DMSP-degrading bacteria in two water masses of Northern Baffin Bay, ASLO meeting, San Juan, Puerto Rico, February, 2011.

Mucci, A., B. Landsard, L.A. Miller, and T.N. Papakyriakou, 2010. CO2 fluxes across the air-sea interface in the southeastern Beaufort Sea:

Ice-free period, J. Geophys. Res., 115, C04003, doi:10.1029/2009JC005330.

Orsi, A.H., G.C. Johnson, and J.L. Bullister, 2009. Circulation, mixing and production of Antarctic Bottom Waters, Prog. Oceanogr., 43, 55-109, doi:10.1016/s0079-6611(99)00004-X.

Randall, K., M. G. Scarratt, M. Levasseur, S. Michaud, H. Xie, and M. Gosselin, 2012. Arctic sea ice: source or sink for nitrous oxide? J. Geophys. Res., 117, C5, doi: 10.1029/2011JC007340.

Rempillo O., Seguin M., Norman A.-L., Scarratt M.G., Michaud S., Chang R., Sjostedt S., Abbatt J., Else B., Papakyriakou T., Sharma S., Grasby, S., Levasseur M., 2011. DMS fluxes and the growth of the biogenic sulphur aerosol component: a study aboard an icebreaker in the Arctic in the fall of 2007 and 2008. J. Geophys. Res., 116, D00S04, doi:10.1029/2011JD016336.

Rysgaard, S., R. N. Glud, M. K. Sejr, J. Bendtsen, and P. B. Christensen, 2007. Inorganic carbon transport during sea ice growth and decay: A carbon pump in polar seas, J. Geophys. Res., 112, C03016, doi:10.1029/2006JC003572.

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Shadwick, E.H., H. Thomas, M. Chierici, B. Else, A. Franson, C. Michel, L.A. Miller, A. Mucci, A. Niemi, T. Papakyriakou, and J-É. Tremblay (2011), Limnol. Oceanogr., 56, 1, 303-322.

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- Effects on CO2 exchange and ocean acidification, J. Geophys. Res.: Oceans, Manuscript accepted.

Steiner, N., Christian, J., Six, K., Sou, T., Williams, B., and Yamamoto-Kawai, M., 2013b. The calcium carbonate saturation state in the Arctic - A CMIP5 model intercomparison. In preparation.

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Publications

(All ArcticNet refereed publications are available on the ASTIS website (http://www.aina.ucalgary.ca/arcticnet/).

Asplin, M., Galley, R.J., Barber, D.G., Papakyriakou, T., and Prinsenberg, S., 2012, Dynamic and thermodynamic implications of ocean swell fracturing on summer Arctic sea ice as a result of Arctic storms., Oral Presentation, ArcticNet AGM, Vancouver, BC.

Carnat, G., Papakyriakou, T., Geilfus, N-X, and 6 others, 2012, Year-round survey of Arctic first-year sea ice physical and textural properties in the Amundsen Gulf (IPY-CFL System Study), Journal of Glaciology.

Elliott, S., Deal, C., Humphries, G., Hunke, E., Jeffery, N., Jin, M., Levasseur, M., and Stefels, J., 2012, Pan-Arctic Simulation of Coupled Nutrient-Sulfur Cycling due to Sea Ice Biology: Preliminary Results, Journal of Geophysical Research: Biogeosciences, G1, DOI: 10.1029/2011JG001649.

Else, B.G.T., Galley, R.J., Lansard, B., Barber, D.G., Brown, K., Miller, L.A., Mucci, A., Papakyriakou, T.N., Tremblay, J.-É., and Rysgaard, S., 2013, Sea ice loss and the changing atmospheric CO2 uptake capacity of the Arctic Ocean: Insights from the southeastern Canada Basin, Geophysical Research Letters.

Else, B.G.T., Galley, R.J., Lansard, B., Barber, D.G., Brown, K., Miller, L.A., Mucci, A., Papakyriakou, T.N., Tremblay, J.-É., and Rysgaard, S., 2012, Sea ice loss and the changing atmospheric CO2 uptake capacity of the Arctic Ocean: insights from the southeastern Canada Basin, Oral Presentation, ArcticNet AGM, Vancouver, BC.

Else, B.G.T., Galley, R.J., Papakyriakou, T.N., Miller, L.A., Mucci, A. and D. Barber, 2012, Sea surface pCO2 cycles and CO2 fluxes at landfast sea ice edges in Amundsen Gulf, Canada, Journal of Geophysical Research: Oceans, 117, doi:10.1029/2011JC007346.

Else, B.G.T., Galley, R.J., Papakyriakou, T.N., Miller, L.A., Mucci, A. and D. Barber, 2012, Sea surface pCO2 cycles and CO2 fluxes at landfast sea ice edges in Amundsen Gulf, Canada, Journal of Geophysical Research: Oceans, 117, C09010, doi: 10.1029/2012JC007901.

Else, B.G.T., Papakyriakou, T.N., Mucci, A., Miller, L.A., Asplin, M.G., Galley, R.J., Barber, D., 2013, An annual air-sea CO2 flux budget for the Cape Bathurst polynya region, Global Biogeochemical Cycles, 2012GB004425.

Galindo, V., Levasseur, M., Scarratt, M., Kiene. R.P., Gosselin, M., Mundy, C.J., 2012, DMSP bacterial metabolism at the ice-water interface during the spring melt period in Arctic, Presentation, Quebec Ocean 10th year anniversary symposium, Montreal, QC.

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Galindo, V., Levasseur, M., Scarratt, M., Mundy, C.J., Gosselin, M., Lizotte, M., Papakiriakou, T., and Michaud, S., 2012, Contribution of ice algae to the marine pool of dimethylsulfoniopropionate (DMSP) in the Arctic., Poster, International Polar Year Conference, Montreal, April 22th-27th 2012.

Galindo, V., Levasseur, M., Scarratt, M., Mundy, C.J., Gosselin, M., Lizotte, M., Papakiriakou, T., and Michaud, S., 2012, DMSP bacterial metabolism at the ice-water interface during the spring melt period in Arctic, Poster, ArcticNet AGM, Vancouver, BC.

Geilfus, N-X, Carnat, G., Dieckmann, G., Halden, N., Nehrke, G., Papakyriakou, T., Tison, J-L, and Delille, B., 2013, First estimates of the contribution of CaCO3 precipitation to the release of CO2 to the atmosphere during young sea ice growth, Journal of Geophysical Research: Oceans, 20112JC007980R.

Geilfus, N.-X., G. Carnat, T. Papakyriakou, J.-L. Tison, B. Else, H. Thomas, E.H. Shadwick and B. Delille, 2012, pCO2 dynamics and related air-ice CO2 fluxes in the Arctic coastal zone (Amundsen Gulf, Beaufort Sea), Journal of Geophysical Research: Oceans, 117, C00G10, doi: 10.1029/2011JC007118.

Gourdal, G., Galindo, V., Levasseur, M., Scarratt, M., Mundy, C.J., Gosselin, M., Lizotte, M., et al, 2012, First measurements of DMSP in Arctic melt pond, Poster, Quebec Ocean 10th year anniversary symposium, Montreal, QC.

Gourdal. G., Galindo, V., Levasseur, M., Scarratt, M., Mundy, C.J., Gosselin, M., Lizotte, M., et al., 2012, First measurements of DMSP in Arctic melt ponds., Poster, ArcticNet AGM, Vancouver, BC.

Lansard, B., Mucci, A., Miller, L.A., Macdonald, R.W., and Gratton, Y., 2012, Seasonal variability of water mass distribution in the southeastern Beaufort Sea determined by total alkalinity and d18O, Journal of Geophysical Research: Oceans, 117, C03003, doi:10.1029/2011JC007299.

Levasseur, M., 2012, Dynamique du DMSP

sympagique lors de la fonte printanière en Arctique, Presentation, Université Libre de Bruxelles.

Luce M, Levasseur, M., Scarratt, M., Michaud, S., Kiene, R., Lovejoy, C., Gosselin, M., Poulin, M., and Gratton, Y., 2012, Fall Distribution and Microbial Metabolism of Dimethylsulfoniopropionate and Dimethylsulfide During the 2007 Arctic Ice Minimum, Journal of Geophysical Research: Oceans, 116, C11, doi: 10.1029/2010JC006914.

Mundy, C.J., Gosselin, M., Gratton, Y., Galindo, V., Brown, K., Campbell, K., Levasseur, M., Barber, D.G., Papakyriakou, T., and Miller, L.A., 2012, The role of environmental factors on under-ice phytoplankton bloom initiation: A case study on landfast sea ice near Resolute Bay, Nunavut, Limnology and Oceanography.

Pind, M., Barber, D., Davelaar, M., Gosselin, M., Miller, L.A., Thomas, H., Tremblay, J.-E, and Papakyriakou, T., 2012, Variability of pCO2 in the surface water across the Canadian Arctic Archipelago, Poster, ArcticNet AGM, Vancouver, BC.

Randall, K., Scarratt, M. G., Levasseur, M., Michaud, S., Xie, H., and Gosselin, M., 2012, Arctic sea ice: source or sink for nitrous oxide?, Journal of Geophysical Research: Oceans, 117,C5, doi: 10.1029/2011JC007340.

Sharma, S., Chan, E., Ishizawa, M., Toom-Sauntry, D., Agnew, T., Gong, S.L., Li, S.M., Leaitch, W.R., Norman, A.-L., Quinn, P.K., Bates, T.S., Levasseur, M., Barrie, L.A., and Maenhaut, W., 2012, Influence of Transport and Ocean Ice Extent on Biogenic Aerosol Sulfur in the Arctic, Journal of Geophysical Research: Atmospheres, 117, D12209, doi:10.1029/2011JD017074.

Shepson P, Ariya P, Deal C, Donaldson DJ, Douglas TA, Loose B, Maksym T, Matrai P, Russell L, Saenz B, Stefels J, Steiner N., 2012, Ocean-Atmosphere-Sea Ice-Snowpack Interactions, Changes, and Feedbacks in Polar Regions: A Scientific Challenge for the 21st Century, EOS, 93, 11, 117-118.

Sjostedt, S.J., Leaitch, W.R., Levasseur, M., Scarratt,

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M., Michaud. S., Menard-Coté, J., and Abbatt, J.P.D., 2012, Evidence for the uptake of acetone and methanol by the Arctic Ocean during late summer DMS events, Journal of Geophysical Research: Atmospheres, 117, D12303, doi:10.1029/2011JD017086.

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carbon exchange dynamics in coastal and marine ecosystems · 2019-06-10 · 3 t 201213 • there...

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