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From 23 October 2007 to 1 August 2008, we made continuous measurements of sea surface partial pressure of CO2 (pCO2sw) in three regions of the southeastern Beaufort Sea (Canada): the Amundsen Gulf, the Banks Island Shelf, and the Mackenzie Shelf. All three regions are seasonally ice covered, with mobile winter ice and an early spring opening that defines them as polynya regions. Amundsen Gulf was characterized by undersaturated pCO2sw (with respect to the atmosphere) in the late fall, followed by an under‐ice increase to near saturation in winter, a return to undersaturation during the spring, and an increase to near saturation in summer. The Banks Island Shelf acted similarly, while the Mackenzie Shelf experienced high supersaturation in the fall, followed by a spring undersaturation and a complex, spatially heterogeneous summer season. None of these patterns are similar to the annual cycle described or proposed for other Arctic polynya regions. We hypothesize that the discrepancy reflects the influence of several previously unconsidered processes including fall phytoplankton blooms, upwelling, winter air‐sea gas exchange, the continental shelf pump, spring nutrient limitation, summer surface warming, horizontal advection, and riverine input. In order to properly predict current and future rates of air‐sea CO2 exchange in such regions, these processes must be considered on a location‐by‐location basis. Key Points The annual pCO2 cycle in the southeastern Beaufort Sea is described for 2007‐2008 The pCO2 cycling in Arctic polynyas is more complex than previously thought Several previously unconsidered processes are shown to control pCO2 in the area

The ocean is a large but uncertain sink of tropospheric ozone. Ozone deposition is controlled partly by its reactions with marine substances, but in situ evidence of this marine biogeochemical control remains sparse. Here we report a novel measurement of ozone uptake efficiency (OUE) from a trans‐Atlantic cruise (50°N to 45°S). Observed OUE for surface waters varied two‐fold and the implied chemical deposition velocity varied from 0.012 to 0.034 cm s−1. Iodide accounted for on average 2/3 of total OUE, with generally higher contributions in tropical waters. The residual OUE, generally higher in temperate waters and positively correlated with biological proxies, was likely due to marine organics. OUE was also measured for 1,000 m waters, which were likely devoid of iodide but contained biologically refractory organics. Unexpectedly, these waters were rather reactive toward ozone, suggesting that surface organics that affect ozone uptake are not all freshly produced by marine biota.

A simplifying assumption in many studies of ocean carbon uptake is that the atmosphere is well‐mixed, such that zonal variations in its carbon dioxide (CO2) content can be neglected in the calculation of air‐sea fluxes. Here, we examine this assumption at various scales to quantify the errors it introduces. For global annual averages, we find that positive and negative errors effectively cancel, so the use of atmospheric zonal‐average CO2 introduces reassuringly small errors in fluxes. However, for millions of square kilometers of the North Pacific and Atlantic that are downwind of the highly industrialized northern hemisphere continents, these biases average to over 6% of the annual ocean uptake and can cause errors of up to 30% on a given day. This work highlights the need to use a high quality, spatially‐resolved atmospheric CO2 product for process studies and for accurate long‐term average maps of ocean carbon uptake. Plain Language Summary Closing the global carbon budget is key to keeping tabs on society's progress toward a stabilized climate. Therefore, oceanographers go to great lengths to reduce uncertainty in the quantification of ocean carbon uptake. While there has been much attention on improving almost every aspect of the calculation of air‐sea exchange of carbon dioxide, one aspect has been seldom examined: How atmospheric carbon dioxide (CO2) concentrations vary across the globe. For instance, westerly winds draw elevated CO2 from Asia and North America over the neighboring oceans. This promotes higher ocean CO2 uptake than would be estimated if we neglect that spatial variation. Luckily, the errors introduced by ignoring spatial variability average to a very small number over large enough scales (though this was not a foregone conclusion, given that the elevated atmospheric concentrations are found over very windy, high ocean uptake regions). However, in the “tailpipe” of the industrialized continents (i.e., the western North Pacific and North Atlantic), neglecting the elevated atmospheric CO2 concentrations would lead to a low bias in ocean carbon uptake estimates. Overall, the work suggests that local ocean carbon uptake studies should measure atmospheric CO2 locally or make use of atmospheric CO2 estimates that resolve spatial variability. Key Points Atmospheric CO2 is elevated downwind of highly industrialized continents, the “tailpipe regions,” east of Asia and North America Atmospheric CO2 anomalies swept over the neighboring ocean enhance ocean uptake above estimates using zonal mean atmospheric CO2 Errors average out over hemispheric‐scales, but introduce important biases on local scales

Air‐sea exchanges across oceanic fronts are critical in powering cloud formation, precipitation, and atmospheric storms. Oceanic submesoscale fronts of scales 1–10 km are characterized by strong sea surface temperature (SST) gradients. However, it remains elusive how submesoscale fronts affect the overlying atmosphere due to a lack of high‐resolution observations or models. Based on rare high‐resolution in situ observations in the Kuroshio Extension region, we quantify the air‐sea exchanges across an oceanic submesoscale front. The cross‐front SST and turbulent heat flux gradients reaches 2.4°C/km and 47 W/m2/km, respectively, far stronger than that typically found in mesoscale‐resolving products. The stronger SST gradient drives substantially stronger air‐sea fluxes and vertical mixing than mesoscale fronts, enhancing cloud formations. The intense air‐sea exchanges across submesoscale fronts are confirmed in idealized model simulations, but not resolved in mesoscale‐resolving climate models. Our finding provides essential knowledge for improving simulations of cloud formation, precipitation, and storms in climate models. Plain Language Summary Oceanic fronts, characterized by large sea surface temperature (SST) gradients, are ubiquitous in the global ocean. Through intense heat and moisture release, these oceanic fronts induce large horizontal gradient of sea level pressure or increasing vertical mixing intensity in the lower atmosphere, are critical in powering cloud formation, precipitation, and atmospheric storms, but are sensitive to SST gradients. Oceanic submesoscale fronts of spatial scales 1–10 km are characterized by strong SST gradients. However, our knowledge of how the submesoscale fronts affect the overlying atmosphere is by and large void, due to a lack of high‐resolution observations or models. Here, based on high‐resolution in situ observations and model simulations, we show that submesoscale fronts drive much stronger air‐sea exchanges and vertical mixing as compared to mesoscale fronts, with significant implications for marine atmosphere boundary layer changes and cloud formations. Limited by the coarse resolution, the intense air‐sea exchanges across submesoscale fronts are not resolved in mesoscale‐resolving climate models. These results highlight the importance of submesoscale air‐sea interactions and call for a proper representation of submesoscale air‐sea exchanges in the next generation of climate models. Key Points Observations show strong gradient in sea surface temperature and turbulent heat flux across a submesoscale oceanic front Submesoscale fronts drive substantially stronger air‐sea fluxes and vertical mixing than mesoscale fronts The intense air‐sea exchanges across submesoscale fronts are not resolved in mesoscale‐resolving climate models

Methanol metabolism can play an important role in marine carbon cycling. We made contemporaneous measurements of methanol concentration and consumption rates in the northwest Pacific Ocean to constrain the pathways and dynamics of methanol cycling. Methanol was detected in relatively low concentrations (<12–391 nM), likely due to rapid biological turnover. Rates of methanol oxidation to CO2 (0.9–130.5 nmol L−1 day−1) were much higher than those of assimilation into biomass (0.09–6.8 nmol L−1 day−1), suggesting that >89.7% of methanol was utilized as an energy source. Surface water acted as a net methanol sink at most sites, with an average flux of 9 μmol L−1 day−1. Atmospheric deposition accounted for 22.7% of microbial methanol consumption in the mixed layer, illustrating that the atmosphere is less important than internal processes for driving methanol cycling in these pelagic waters. Plain Language Summary Methanol is one of the most abundant oxygenated volatile organic compounds in the atmosphere and microbial methanol metabolism is an important part of the marine carbon cycle. However, only a limited number of studies describe methanol cycling in marine waters, and the sources and sinks of methanol remain largely unconstrained in the Pacific Ocean. We investigated the distribution and microbial consumption of methanol in the Kuroshio‐Oyashio extension region of northwest Pacific Ocean. Methanol was used primarily as an energy source and the rapid biological turnover of methanol contributed to relatively low‐standing stocks of methanol. Air‐sea flux estimates suggested that the atmosphere was a net source of methanol to the study area. Compared to in situ production and consumption rates, air‐sea exchange represented a less important process for methanol cycling in the mixed layer. Our results add to the global database of methanol concentrations and help to constrain the biological sources and sinks of methanol in the surface ocean. Key Points Methanol was detected in relatively low concentrations due to rapid biological consumption in the Kuroshio‐Oyashio extension region Much higher oxidation rates than assimilation rates suggested methanol was predominantly used as an energy source Atmospheric deposition is a source of methanol in the mixed layer and accounted for 22.7% of microbial methanol consumption

During the 2007 UK SOLAS Deep Ocean Gas Exchange Experiment in the northeast Atlantic Ocean, we conducted the first ever study of the effect of a deliberately released surfactant (oleyl alcohol) on gas transfer velocities (kw) in the open ocean. Exchange rates were estimated with the 3He/SF6 dual tracer technique and from measured sea‐to‐air DMS fluxes and surface water concentrations. A total of seven kw estimates derived from 3He/SF6 were made, two of which were deemed to be influenced by the surfactant. These exhibited suppression from ∼5% to 55% at intermediate wind speeds (U10) in the range 7.2–10.7 m s−1. Similarly, kw determined from DMS data (kDMS) was also depressed by the surfactant; suppression ranged from ∼39% at 5.0 m s−1 to ∼24% at 10.8 m s−1. Surfactant thus has the potential to measurably suppress gas exchange rates even at moderate to high wind speeds. Key Points The first in situ study of the effect of surfactants on air‐sea gas exchange The 3He/SF6 and DMS flux‐derived estimates of kw were suppressed by the surfactant Strong suppression of kw by the surfactant, even at moderate‐high wind speeds

Updates for the Coupled Ocean‐Atmosphere Response Experiment (COARE) physically based meteorological and gas transfer bulk flux algorithms are examined. The current versions are summarized and a generalization of the gas transfer codes to 79 gases is described. The current meteorological version COARE3.0 was compared with a collection of 26,700 covariance observations of drag and heat transfer coefficients (compiled from three independent research groups). The algorithm agreed on average to within 5% with observations for a wind speed range of 2 to 18 m s−1. Covariance observations of CO2 and dimethyl sulfide (DMS) gas transfer velocity k were normalized to Schmidt number 660 and compared to an ensemble of gas flux observations from six research groups and nine field programs. A reasonable fit of the mean k660 versus U10n values was obtained for both CO2 and DMS with a new version of the COARE gas transfer algorithm (designated COAREG3.1) using friction velocity associated with viscous (tangential) stress, u*ν, in the nonbubble term. In the wind speed range 5 to 16 m s−1, tracer‐derived estimates of k660 are 10% to 20% lower than the CO2 covariance estimates presented here. Key Points COARE algorithm fits observed drag and heat transfer coefficients COARE algorithm fits observed CO2 and DMS covariance k coefficients The use of a tangential friction velocity improves the fits to CO2 and DMS

Acetone is one of the most abundant carbonyl compounds in the atmosphere and it plays an important role in atmospheric chemistry. The role of the ocean in the global atmospheric acetone budget is highly uncertain, with past studies reaching opposite conclusions as to whether the ocean is a source or sink. Here we use a global 3‐D chemical transport model (GEOS‐Chem) simulation of atmospheric acetone to evaluate the role of air‐sea exchange in the global budget. Inclusion of updated (slower) photolysis loss in the model means that a large net ocean source is not needed to explain observed acetone in marine air. We find that a simulation with a fixed seawater acetone concentration of 15 nM based on observations can reproduce the observed global patterns of atmospheric concentrations and air‐sea fluxes. The Northern Hemisphere oceans are a net sink for acetone while the tropical oceans are a net source. On a global scale the ocean is in near‐equilibrium with the atmosphere. Prescribing an ocean concentration of acetone as a boundary condition in the model assumes that ocean concentrations are controlled by internal production and loss, rather than by air‐sea exchange. An implication is that the ocean plays a major role in controlling atmospheric acetone. This hypothesis needs to be tested by better quantification of oceanic acetone sources and sinks. Key Points We updated the global atmospheric acetone budget using a global model We can reproduce observed marine atmospheric concentrations and air‐sea fluxes The ocean plays a major role in controlling atmospheric acetone

In the Southern Ocean Gas Exchange Experiment (SO GasEx), we measured an atmospheric dimethylsulfide (DMS) concentration of 118 ± 54 pptv (1σ), a DMS sea‐to‐air flux of 2.9 ± 2.1 μmol m−2 d−1 by eddy covariance, and a seawater DMS concentration of 1.6 ± 0.7 nM. Dividing flux by the concurrent air‐sea concentration difference yields the transfer velocity of DMS (kDMS). The kDMS in the Southern Ocean was significantly lower than previous measurements in the equatorial east Pacific, Sargasso Sea, northeast Atlantic, and southeast Pacific. Normalizing kDMS for the temperature dependence in waterside diffusivity and solubility results in better agreement among various field studies and suggests that the low kDMS in the Southern Ocean is primarily due to colder temperatures. The higher solubility of DMS at a lower temperature results in greater airside control and less transfer of the gas by bubbles formed from breaking waves. The final normalized DMS transfer velocity is similar to k of less soluble gases such as carbon dioxide in low‐to‐moderate winds; in high winds, DMS transfer velocity is significantly lower because of the reduced bubble‐mediated transfer. Key Points DMS transfer velocity is lower than those of insoluble gases in high winds DMS transfer velocity shows complex temperature and stability dependence NOAA COARE gas transfer model predicts DMS transfer well

Surface seawater and boundary layer air samples were collected on the icebreaker Xuelong (Snow Dragon) during the Fourth Chinese Arctic Research Expedition (CHINARE2010) cruise in the North Pacific and Arctic Oceans during 2010. Samples were analyzed for organochlorine pesticides (OCPs), including three isomers of hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), and two isomers of heptachlor epoxide. The gaseous total HCH (ΣHCHs) concentrations were approximately four times lower (average 12.0 pg m−3) than those measured during CHINARE2008 (average 51.4 pg m−3), but were comparable to those measured during CHINARE2003 (average 13.4 pg m−3) in the same study area. These changes are consistent with the evident retreat of sea ice coverage from 2003 to 2008 and increase of sea ice coverage from 2008 to 2009 and 2010. Gaseous β‐HCH concentrations in the atmosphere were typically below the method detection limit, consistent with the expectation that ocean currents provide the main transport pathway for β‐HCH into the Arctic. The concentrations of all dissolved HCH isomers in seawater increase with increasing latitude, and levels of dissolved HCB also increase (from 5.7 to 7.1 pg L−1) at high latitudes (above 73°N). These results illustrate the role of cold condensation processes in the transport of OCPs. The observed air–sea gas exchange gradients in the Arctic Ocean mainly favored net deposition of OCPs, with the exception of those for β‐HCH, which favored volatilization. Key Points Air‐sea exchanges were first measured in Arctic Beta‐HCH suggests a net deposition process HCB is considered the closest to equilibrium