Surface Ocean Lower Atmosphere Study Research Articles

An aerosol odyssey: Navigating nutrient flux changes to marine ecosystems

This perspective piece on aerosol deposition to marine ecosystems and the related impacts on biogeochemical cycles forms part of a larger Surface Ocean Lower Atmosphere Study status-of-the-science special edition. A large body of recent reviews has comprehensively covered different aspects of this topic. Here, we aim to take a fresh approach by reviewing recent research to identify potential foundations for future study. We have purposefully chosen to discuss aerosol nutrient and pollutant fluxes both in terms of the journey that different aerosol particles take and that of the surrounding scientific field exploring them. To do so, we explore some of the major tools, knowledge, and partnerships we believe are required to aid advancing this highly interdisciplinary field of research. We recognize that significant gaps persist in our understanding of how far aerosol deposition modulates marine biogeochemical cycles and thus climate. This uncertainty increases as socioeconomic pressures, climate change, and technological advancements continue to change how we live and interact with the marine environment. Despite this, recent advances in modeling techniques, satellite remote sensing, and field observations have provided valuable insights into the spatial and temporal variability of aerosol deposition across the world’s ocean. With the UN Ocean Decade and sustainable development goals in sight, it becomes essential that the community prioritizes the use of a wide variety of tools, knowledge, and partnerships to advance understanding. It is through a collaborative and sustained effort that we hope the community can address the gaps in our understanding of the complex interactions between aerosol particles, marine ecosystems, and biogeochemical cycles.

Polar oceans and sea ice in a changing climate

Polar oceans and sea ice cover 15% of the Earth’s ocean surface, and the environment is changing rapidly at both poles. Improving knowledge on the interactions between the atmospheric and oceanic realms in the polar regions, a Surface Ocean–Lower Atmosphere Study (SOLAS) project key focus, is essential to understanding the Earth system in the context of climate change. However, our ability to monitor the pace and magnitude of changes in the polar regions and evaluate their impacts for the rest of the globe is limited by both remoteness and sea-ice coverage. Sea ice not only supports biological activity and mediates gas and aerosol exchange but can also hinder some in-situ and remote sensing observations. While satellite remote sensing provides the baseline climate record for sea-ice properties and extent, these techniques cannot provide key variables within and below sea ice. Recent robotics, modeling, and in-situ measurement advances have opened new possibilities for understanding the ocean–sea ice–atmosphere system, but critical knowledge gaps remain. Seasonal and long-term observations are clearly lacking across all variables and phases. Observational and modeling efforts across the sea-ice, ocean, and atmospheric domains must be better linked to achieve a system-level understanding of polar ocean and sea-ice environments. As polar oceans are warming and sea ice is becoming thinner and more ephemeral than before, dramatic changes over a suite of physicochemical and biogeochemical processes are expected, if not already underway. These changes in sea-ice and ocean conditions will affect atmospheric processes by modifying the production of aerosols, aerosol precursors, reactive halogens and oxidants, and the exchange of greenhouse gases. Quantifying which processes will be enhanced or reduced by climate change calls for tailored monitoring programs for high-latitude ocean environments. Open questions in this coupled system will be best resolved by leveraging ongoing international and multidisciplinary programs, such as efforts led by SOLAS, to link research across the ocean–sea ice–atmosphere interface.

Ocean negative carbon emissions: A new UN Decade program

Ocean negative carbon emissions: A new UN Decade program

From Monodisciplinary via Multidisciplinary to an Interdisciplinary Approach Investigating Air-Sea Interactions – a SOLAS Initiative

Understanding the physical and biogeochemical interactions and feedbacks between the ocean and atmosphere is a vital component of environmental and Earth system research. The ability to predict and respond to future environmental change relies on a detailed understanding of these processes. The Surface Ocean-Lower Atmosphere Study (SOLAS) is an international research platform that focuses on the study of ocean-atmosphere interactions, for which Future Earth is a sponsor. SOLAS instigated a collaborative initiative process to connect efforts in the natural and social sciences related to these processes, as a contribution to the emerging Future Earth Ocean Knowledge-Action Network (Ocean KAN). This is imperative because many of the recent changes in the Earth system are anthropogenic. An understanding of adaptation and counteracting measures requires an alliance of scientists from both domains to bridge the gap between science and policy. To this end, three SOLAS research areas were targeted for a case study to determine a more effective method of interdisciplinary research: valuing carbon and the ocean’s role; air-sea interactions, policy and stewardship; and, air-sea interactions and the shipping industry.

ASLO 2020 Award Winners

<scp>ASLO</scp> 2020 Award Winners

Author Correction: Reduced air–sea CO2 exchange in the Atlantic Ocean due to biological surfactants

In the version of this Article originally published, in the ‘Acknowledgements’ section the authors neglected to include the following text: “The Surface Ocean CO2 Atlas (SOCAT) is an international effort, endorsed by the International Ocean Carbon Coordination Project (IOCCP), the Surface Ocean Lower Atmosphere Study (SOLAS) and the Integrated Marine Biosphere Research (IMBeR) programme, to deliver a uniformly quality-controlled surface ocean CO2 database. The many researchers and funding agencies responsible for the collection of data and quality control are thanked for their contributions to SOCAT.” This has now been added in the online versions of the Article.

Harnessing remote sensing to address critical science questions on ocean-atmosphere interactions

Earth observing systems have proven to be a unique source of long-term synoptic information on numerous physical, chemical and biological parameters on a global scale. Merging this information for integrated studies that peruse key questions about the ocean-atmosphere interface is, however, very challenging. Such studies require interdisciplinary frameworks and novel insights into ways to address the problem. We present here a perspective review on how current and emerging remote sensing technologies could help address two scientific questions within the Surface Ocean-Lower Atmosphere Study (SOLAS) science plan: (1) to what extent does upper-ocean biology affect the composition and radiative properties of the marine boundary layer; and (2) to what extent does upper-ocean turbulence drive fluxes of mass and energy at the air-sea interface. We provide a thorough review of how these questions have been addressed and discuss novel potential avenues using multiplatform space-borne missions, from visible to microwave, active and passive sensors.

Surface ocean-lower atmosphere study: Scientific synthesis and contribution to Earth system science

The domain of the surface ocean and lower atmosphere is a complex, highly dynamic component of the Earth system. Better understanding of the physics and biogeochemistry of the air–sea interface and the processes that control the exchange of mass and energy across that boundary define the scope of the Surface Ocean-Lower Atmosphere Study (SOLAS) project. The scientific questions driving SOLAS research, as laid out in the SOLAS Science Plan and Implementation Strategy for the period 2004–2014, are highly challenging, inherently multidisciplinary and broad. During that decade, SOLAS has significantly advanced our knowledge. Discoveries related to the physics of exchange, global trace gas budgets and atmospheric chemistry, the CLAW hypothesis (named after its authors, Charlson, Lovelock, Andreae and Warren), and the influence of nutrients and ocean productivity on important biogeochemical cycles, have substantially changed our views of how the Earth system works and revealed knowledge gaps in our understanding. As such SOLAS has been instrumental in contributing to the International Geosphere–Biosphere Programme (IGBP) mission of identification and assessment of risks posed to society and ecosystems by major changes in the Earth’s biological, chemical and physical cycles and processes during the Anthropocene epoch. SOLAS is a bottom-up organization, whose scientific priorities evolve in response to scientific developments and community needs, which has led to the launch of a new 10-year phase. SOLAS (2015–2025) will focus on five core science themes that will provide a scientific basis for understanding and projecting future environmental change and for developing tools to inform societal decision-making.

Near-surface measurements of sea spray aerosol production over whitecaps in the open ocean

Abstract. Simultaneous measurements of near-surface aerosol (0.12 &lt; R &lt; 9.25 μm) and bubble spectra (13 &lt; R &lt; 620 μm) were made during five buoy deployments in the open ocean of the North Atlantic and used to estimate aerosol fluxes per unit area of whitecap. The measurements were made during two cruises as part of the Sea Spray, Gas Flux, and Whitecaps (SEASAW) project, a UK contribution to the international Surface Ocean Lower Atmosphere Study (SOLAS) program. The mean bubble number concentrations for each deployment are in broad agreement with other open ocean spectra and are consistently one to two orders of magnitude lower than surf zone studies. Production fluxes per unit area of whitecap are estimated from the mean aerosol concentration for each buoy deployment. They are found to increase with wind speed, and span the range of values found by previous laboratory and surf-zone studies for particles with radius at 80% relative humidity, R80 &lt; 1 μm, but to drop off more rapidly with increasing particle size for larger particles. Estimates of the mean sea spray flux were made by scaling the whitecap production fluxes with in situ estimates of whitecap fraction. The sea spray fluxes are also compared with simultaneous individual eddy covariance flux estimates, and with a sea spray source function derived from them.

Eddy covariance measurements of the sea spray aerosol flux over the open ocean

Direct eddy covariance measurements of size‐segregated sea spray aerosol fluxes over the open Atlantic Ocean are presented, along with a source function derived from them for a wind speed range of 4 to 18 m s−1 and a size range of 0.176 &lt; R80 &lt; 6.61 μm. This is in broad agreement with other recent estimates of the source function over this size range but shows a more rapid decrease with size above R80 = 2 μm than most other functions. The measurements were made during a 3 week cruise in the North Atlantic as part of the UK contribution to the international Surface Ocean–Lower Atmosphere Study (SOLAS) program. They utilized the new high‐rate Compact Lightweight Aerosol Spectrometer Probe (CLASP), providing a 16‐channel size spectrum (0.17 &lt;Ramb &lt; 9.5 μm) at 10 Hz, collocated with a sonic anemometer. The measurements demonstrate the high variability in sea spray aerosol flux compared with other air‐sea fluxes, both between individual estimates and in the scales contributing to the flux.

Surface Ocean–Lower Atmosphere Processes

No system exists in isolation, and the ocean is no different. Understanding the mechanics directing a system as complicated as the ocean takes an interdisciplinary effort and well‐controlled studies. The Surface Ocean–Lower Atmosphere Study (SOLAS) program is an international effort to make sense of the physical and biogeochemical interactions that take place between the air and the sea. Having scientists ready to dissect these interactions will be increasingly important as the world begins to consider deliberately manipulating the system in an attempt to combat climate change. The AGU Monograph Surface Ocean–Lower Atmosphere Processes, edited by Corinne Le Quéré and Eric S. Saltzman, looks at the increasingly important interactions occurring at the boundary between these two systems. In this interview, Eos talks to Corinne Le Quéré.

Upper ocean bubble measurements from the NE Pacific and estimates of their role in air‐sea gas transfer of the weakly soluble gases nitrogen and oxygen

Simultaneous observations of upper‐ocean bubble clouds, and dissolved gaseous nitrogen (N2) and oxygen (O2) from three winter storms are presented and analyzed. The data were collected on the Canadian Surface Ocean Lower Atmosphere Study (C‐SOLAS) mooring located near Ocean Station Papa (OSP) at 50°N, 145°W in the NE Pacific during winter of 2003/2004. The bubble field was measured using an upward looking 200 kHz echosounder. Direct estimates of bubble mediated gas fluxes were made using assumed bubble size spectra and the upward looking echosounder data. A one‐dimensional biogeochemical model was used to help compare data and various existing models of bubble mediated air‐sea gas exchange. The direct bubble flux calculations show an approximate quadratic/cubic dependence on mean bubble penetration depth. After scaling from N2/O2 to carbon dioxide, near surface, nonsupersaturating, air‐sea transfer rates, KT, for U10 &gt; 12 m s−1 fall between quadratic and cubic relationships. Estimates of the subsurface bubble induced air injection flux, VT, show an approximate quadratic/cubic dependence on mean bubble penetration depth. Both KT and VT are much higher than those measured during Hurricane Frances over the wind speed range 12 &lt; U10 &lt; 23 m s−1. This result implies that over the open ocean and this wind speed range, older and more developed seas which occur during winter storms are more effective in exchanging gases between the atmosphere and ocean than younger less developed seas which occur during the rapid passage of a hurricane.

Changes in iron speciation following a Saharan dust event in the tropical North Atlantic Ocean

Concentrations of dissolved iron (DFe) and Fe-binding ligands were determined in the tropical Northeast Atlantic Ocean (12–30°N, 21–29°W) as part of the UK-SOLAS (Surface Ocean Lower Atmosphere Study) cruise Poseidon 332 (P332) in January–February 2006. The surface water DFe concentrations varied between 0.1 and 0.4 nM with an average of 0.22 ± 0.05 nM ( n = 159). The surface water concentrations of total Fe-binding ligands varied between 0.82 and 1.46 nM with an average of 1.11 ± 0.14 nM ( n = 33). The concentration of uncomplexed Fe-binding ligands varied between 0.64 and 1.35 nM with an average of 0.90 ± 0.14 nM ( n = 33). Thus, on average 81% of the total Fe-binding ligand concentration was uncomplexed. The average logarithmic conditional stability constant of the pool of Fe-binding ligands was 22.85 ± 0.38 with respect to Fe 3+ ( n = 33). A transect (12°N, 26°W to 16°N, 25.3°W) was sailed during a small Saharan dust event and repeated a week later. Following the dust event, the concentration of DFe increased from 0.20 ± 0.026 nM ( n = 125) to 0.25 ± 0.028 ( n = 17) and the concentration of free Fe-binding ligands decreased from 1.15 ± 0.15 ( n = 4) to 0.89 ± 0.10 ( n = 4) nM. Furthermore, the logarithmic stability constants of the Fe-binding ligands south of the Cape Verde islands were distinctively lower than north of the islands. The absence of a change in the logarithmic stability constant after the dust event south of the Cape Verde islands suggests that there was no significant atmospheric input of new Fe-binding ligands during this dust event.

Introduction to special section: Results of the Meteor 55: Tropical SOLAS Expedition

This special section presents results from an interdisciplinary research cruise to the northern tropical Atlantic Ocean, which took place in October–November 2002. The cruise was planned as a pilot study for the international Surface Ocean – Lower Atmosphere Study (SOLAS) project. This introduction summarizes the goals as well as the hydrographic and atmospheric setting of the expedition. We also present a brief review of the findings published in this section and elsewhere concerning controls on trace gas fluxes and the biogeochemical significance of dust composition and deposition.

Short residence time for iron in surface seawater impacted by atmospheric dry deposition from Saharan dust events

Measurements of dissolved (DFe) and total iron (TFe) in the upper water column are presented from the German SOLAS (Surface Ocean ‐ Lower Atmosphere Study) cruise (M55), along a west to east transect at 10°N, in the equatorial Atlantic in October/November 2002. Aerosol samples were collected simultaneously during this time and are used to estimate an iron flux to the surface waters. Resulting flux estimates combined with iron inventories in the near surface waters reveal extremely short fractional mean residence times (6–62 days) for total (dissolved and particulate) iron in waters directly under the path of Saharan dust plumes. These results suggest that individual dust storms can supply a significant amount of the present iron upper water column inventory which is subsequent rapidly removed by aggregation and sinking.

Nitrous oxide in the surface layer of the tropical North Atlantic Ocean along a west to east transect

Nitrous oxide (N2O) was measured during the first German SOLAS (Surface Ocean – Lower Atmosphere Study) cruise in the tropical North Atlantic Ocean on board R/V Meteor during October/November 2002. About 900 atmospheric and dissolved N2O measurements were performed with a semi‐continuous GC‐ECD system equipped with a seawater‐gas equilibrator. Surface waters along the main transect at 10°N showed no distinct longitudinal gradient. Instead, N2O saturations were highly variable ranging from 97% to 118% (in the Guinea Dome Area, 11°N, 24°W). When approaching the continental shelf of West Africa, N2O surface saturations went up to 113%. N2O saturations in the region of the equatorial upwelling (at 0–1.5°N, 23.5–26°W) were correlated with decreasing sea surface temperatures and showed saturations up to 109%. The overall mean N2O saturation was 104 ± 4% indicating that the tropical North Atlantic Ocean is a net source of atmospheric N2O.