Special Issue "Ocean-Atmosphere Interaction"

A special issue of Geosciences (ISSN 2076-3263). This special issue belongs to the section "Geophysics".

Deadline for manuscript submissions: closed (10 December 2018)

Special Issue Editor

Guest Editor
Dr. Raquel Somavilla Cabrillo

IEO, Centro Oceanográfico de Gijón
Website | E-Mail
Interests: ocean climate; ocean-atmosphere interaction; upper ocean variability; ocean mixed layer and stratification; ocean circulation; deep waters; ocean ventilation; mid-latitudes; polar regions; biogeochemistry; physical-biological coupling; climate; climate change

Special Issue Information

Dear Colleagues,

Earth climate and weather are known to be strongly affected by air–sea exchanges of heat and moisture, since the ocean covers more than 70% of the Earth surface and accumulates 93% of the energy in the Earth Climate System. In addition, the global ocean, not only absorbs, stores, and redistributes vast amounts of heat shaping the mean climate of the Earth, but also of carbon, and 50% of the oxygen in Earth’s atmosphere is produced in the upper layers of the ocean by phytoplankton. Thus, major advances in our knowledge of ocean–atmosphere interaction in the last decades have revealed the relevance of the exchange not only of energy, but of gases and particles across the air–sea interface in global budgets. Growing evidence shows that these exchanges are controlled by a variety of physical, chemical and biological processes that operate across a broad range of spatial and temporal scales in the upper ocean and lower atmosphere. This improved understanding of ocean-atmosphere interaction processes has been the result of interdisciplinary observation efforts including a wide range of measurements (oceanographic sections, buoys, Argo floats, gliders, autonomous profilers, etc.) and its combination with models that assimilate such data. This Special Issue on ocean–atmosphere interaction welcomes original research related to observed and modelled magnitude and variability of air–sea exchanges and associated control processes in the upper ocean and lower atmosphere.

Dr. Raquel Somavilla Cabrillo
Guest Editor

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Keywords

  • Ocean-atmosphere interaction
  • Air-sea exchanges
  • Processes
  • Upper Ocean
  • Lower Atmosphere
  • Biogeochemistry
  • Climate

Published Papers (6 papers)

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Research

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Open AccessArticle
Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO2 Fluxes
Geosciences 2019, 9(5), 230; https://doi.org/10.3390/geosciences9050230 (registering DOI)
Received: 15 March 2019 / Revised: 6 May 2019 / Accepted: 13 May 2019 / Published: 20 May 2019
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Abstract
Carbon dioxide (CO2) fluxes between the ocean and atmosphere (FCO2) are commonly computed from differences between their partial pressures of CO2pCO2) and the gas transfer velocity (k). Commonly used wind-based parameterizations [...] Read more.
Carbon dioxide (CO2) fluxes between the ocean and atmosphere (FCO2) are commonly computed from differences between their partial pressures of CO2pCO2) and the gas transfer velocity (k). Commonly used wind-based parameterizations for k imply a zero intercept, although in situ field data below 4 m s−1 are scarce. Considering a global average wind speed over the ocean of 6.6 m s−1, a nonzero intercept might have a significant impact on global FCO2. Here, we present a database of 245 in situ measurements of k obtained with the floating chamber technique (Sniffle), 190 of which have wind speeds lower than 4 m s−1. A quadratic parameterization with wind speed and a nonzero intercept resulted in the best fit for k. We further tested FCO2 calculated with a different parameterization with a complementary pCO2 observation-based product. Furthermore, we ran a simulation in a well-tested ocean model of intermediate complexity to test the implications of different gas transfer velocity parameterizations for the natural carbon cycle. The global ocean observation-based analysis suggests that ignoring a nonzero intercept results in an ocean-sink increase of 0.73 Gt C yr−1. This corresponds to a 28% higher uptake of CO2 compared with the flux calculated from a parameterization with a nonzero intercept. The differences in FCO2 were higher in the case of low wind conditions and large ΔpCO2 between the ocean and atmosphere. Such conditions occur frequently in the Tropics. Full article
(This article belongs to the Special Issue Ocean-Atmosphere Interaction)
Open AccessArticle
Atmospheric Control of Deep Chlorophyll Maximum Development
Geosciences 2019, 9(4), 178; https://doi.org/10.3390/geosciences9040178
Received: 21 January 2019 / Revised: 5 April 2019 / Accepted: 11 April 2019 / Published: 17 April 2019
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Abstract
The evolution of the near-surface phytoplankton bloom towards a Deep Chlorophyll Maximum (DCM) in mid-latitudes and subpolar regions of the global ocean is a well-known biological feature. However, our knowledge about the exact mechanism that determines the end of the bloom and its [...] Read more.
The evolution of the near-surface phytoplankton bloom towards a Deep Chlorophyll Maximum (DCM) in mid-latitudes and subpolar regions of the global ocean is a well-known biological feature. However, our knowledge about the exact mechanism that determines the end of the bloom and its irreversible evolution towards a DCM is still limited. In this work, combining satellite and in-situ oceanographic data together with reanalysis data, we investigate why and when this transition between the near-surface phytoplankton bloom and the development of a DCM occurs. For this aim, we investigate the links between changes in air-sea heat exchanges, the near-surface signature of phytoplankton bloom, and the water column vertical structure by calculating the mixed layer depth (MLD) and depth of the DCM on hydrographic and chlorophyll profiles. We find that the occurrence of the last convective mixing event (heat loss by the ocean surface) at the end of the spring which is able to reach the base of the MLD and inject new nutrients into the mixed layer marks the end of the near-surface bloom and its transition towards a DCM. Identified in this way, the spring bloom duration and the start of the transition towards a DCM can be systematically and objectively determined, providing sensitive indexes of climate and ecosystem variability. Full article
(This article belongs to the Special Issue Ocean-Atmosphere Interaction)
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Open AccessArticle
Local Variability of CO2 Partial Pressure in a Mid-Latitude Mesotidal Estuarine System (Tagus Estuary, Portugal)
Geosciences 2018, 8(12), 460; https://doi.org/10.3390/geosciences8120460
Received: 23 October 2018 / Revised: 29 November 2018 / Accepted: 1 December 2018 / Published: 5 December 2018
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Abstract
Estuaries play a crucial role in regional carbon cycling. Until now, accurate estimations of the impact of environmental variables on estuarine air–water CO2 fluxes have been mostly characterized by a low spatial-temporal sampling resolution. This study reports on the variations of CO [...] Read more.
Estuaries play a crucial role in regional carbon cycling. Until now, accurate estimations of the impact of environmental variables on estuarine air–water CO2 fluxes have been mostly characterized by a low spatial-temporal sampling resolution. This study reports on the variations of CO2 partial pressure (pCO2) and related environmental parameters, at both tidal and seasonal temporal scales, in the surface seawater of a station located in the lower section of the Tagus estuary, Portugal. The study was carried out from February to December 2007. Air–water CO2 fluxes suggest that the lower estuary acted as a relatively weak source of CO2 to the atmosphere, with an average rate of 7.2 mol∙m−2∙year−1, with highest fluxes occurring in winter. Over a tidal cycle, pCO2 was mainly influenced by tidal-induced mixing. Results suggest an influence of upper and central estuary inputs with higher pCO2 values. pCO2 varied seasonally, with values decreasing from ~890 µatm in winter to ~400 µatm in summer and increasing again to ~990 µatm in autumn. The generalized linear model (GLM) applied to the data set explained 69.3% of the pCO2 variability, pointing to the thermodynamic effect of temperature and biological activity as the most relevant processes in CO2 dynamics. Tidal variation of pCO2 corresponded to ~35% of its seasonal variability, denoting the importance of tide conditions on the dynamics of inorganic carbon. Results showed distinct patterns in the dynamics of CO2 at the tidal scale. This outcome suggests that disregarding tidal variability in the use of seasonal data sets may lead to significant errors in annual carbon budget estimations. Full article
(This article belongs to the Special Issue Ocean-Atmosphere Interaction)
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Open AccessArticle
Sea-Air CO2 Exchange in the SW Iberian Upwelling System during Two Contrasting Climate Cycles: 860–780 ka and 630–520 ka
Geosciences 2018, 8(12), 454; https://doi.org/10.3390/geosciences8120454
Received: 4 September 2018 / Revised: 29 November 2018 / Accepted: 1 December 2018 / Published: 4 December 2018
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Abstract
Analysis of planktonic and benthic foraminifers’ accumulation rates from the Iberian margin reveal a substantial change in the biogenic ocean-atmosphere CO2 exchange during the Mid-Pleistocene Transition (MPT; ~800–650 ka from present). Such changes resulted from the major reorganisations in both surface and [...] Read more.
Analysis of planktonic and benthic foraminifers’ accumulation rates from the Iberian margin reveal a substantial change in the biogenic ocean-atmosphere CO2 exchange during the Mid-Pleistocene Transition (MPT; ~800–650 ka from present). Such changes resulted from the major reorganisations in both surface and deep-water circulation that occurred in the North Atlantic at the time, and affected the behaviour of this upwelling region as a CO2 uptake/release area during climate cycles before and after the MPT. During Marine Isotope Stages (MIS) 21-MIS 20 (860–780 ka), this margin acted mostly as an uptake area during interglacials and early glacials. During glacial maxima and terminations it would be neutral because, although surface production and export were very low, carbon storage occurred at the seafloor. During MIS 15-MIS 14 (630–520 ka), the pattern was the opposite, and the Iberian margin worked as a neutral, or as a source area during most interglacials, while during glacials it acted as an important uptake area. Present findings support the idea that glacial/interglacial atmospheric pCO2 oscillations are partly driven by alterations in the meridional overturning circulation that results in substantial variations of the biological pump, and carbon sequestration rate, in some high-productivity regions. Full article
(This article belongs to the Special Issue Ocean-Atmosphere Interaction)
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Review

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Open AccessReview
Oceanic Impact on European Climate Changes during the Quaternary
Geosciences 2019, 9(3), 119; https://doi.org/10.3390/geosciences9030119
Received: 28 January 2019 / Revised: 1 March 2019 / Accepted: 5 March 2019 / Published: 8 March 2019
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Abstract
Integrative studies on paleoclimate variations over oceanic and continental regions are scarce. Though it is known that Earth’s climate is strongly affected by sea-air exchanges of heat and moisture, the role of oceans in climate variations over land remains relatively unexplored. With the [...] Read more.
Integrative studies on paleoclimate variations over oceanic and continental regions are scarce. Though it is known that Earth’s climate is strongly affected by sea-air exchanges of heat and moisture, the role of oceans in climate variations over land remains relatively unexplored. With the aim to unveil this influence, the present work studies major climate oscillations in the North Atlantic region and Europe during the Quaternary, focusing on the oceanic mechanisms that were related to them. During this period, the European climate experienced long-term and wide-amplitude glacial-interglacial oscillations. A covariance between the North Atlantic sea surface temperature and climate signals over the continent is especially observed in Southern Europe. The most severe and drastic climate changes occurred in association to deglaciations, as a consequence of major oceanographic reorganizations that affected atmospheric circulation and ocean-atmosphere heat-flow, which led to variation of temperature and precipitation inland. Most deglaciations began when Northern Hemisphere summer insolation was maximal. Increased heating facilitated the rapid ice-sheet collapse and the massive release of fresh water into the Northern Atlantic, which triggered the weakening or even the shutdown of the North Atlantic Deep Water (NADW) formation. Though the extension of ice-sheets determined the high-latitude European climate, the climate was more influenced by rapid variations of ice volume, deep-water formation rate, and oceanic and atmospheric circulation in middle and subtropical latitudes. In consequence, the coldest stadials in the mid-latitude North Atlantic and Europe since the early Pleistocene coincided with Terminations (glacial/interglacial transitions) and lesser ice-sheet depletions. They were related with decreases in the NADW formation rate that occurred at these times and the subsequent advection of subpolar waters along the western European margin. In Southern Europe, steppe communities substituted temperate forests. Once the freshwater perturbation stopped and the overturning circulation resumed, very rapid and wide-amplitude warming episodes occurred (interstadials). On the continent, raised temperature and precipitations allowed the rapid expansion of moisture-requiring vegetation. Full article
(This article belongs to the Special Issue Ocean-Atmosphere Interaction)
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Other

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Open AccessPerspective
Plastic Accumulation in the Sea Surface Microlayer: An Experiment-Based Perspective for Future Studies
Geosciences 2019, 9(2), 66; https://doi.org/10.3390/geosciences9020066
Received: 26 November 2018 / Revised: 29 December 2018 / Accepted: 26 January 2019 / Published: 29 January 2019
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Abstract
Plastic particles are ubiquitous in the marine environment. Given their low density, they have the tendency to float on the sea surface, with possible impacts on the sea surface microlayer (SML). The SML is an enriched biofilm of marine organic matter, that plays [...] Read more.
Plastic particles are ubiquitous in the marine environment. Given their low density, they have the tendency to float on the sea surface, with possible impacts on the sea surface microlayer (SML). The SML is an enriched biofilm of marine organic matter, that plays a key role in biochemical and photochemical processes, as well as controlling gas exchange between the ocean and the atmosphere. Recent studies indicate that plastics can interfere with the microbial cycling of carbon. However, studies on microplastic accumulation in the SML are limited, and their effects on organic matter cycling in the surface ocean are poorly understood. To explore potential dynamics in this key ocean compartment, we ran a controlled experiment with standard microplastics in the surface and bulk water of a marine monoculture. Bacterial abundance, chromophoric dissolved organic matter (CDOM), and oxygen concentrations were measured. The results indicate an accumulation of CDOM in the SML and immediate underlying water when microplastic particles are present, as well as an enhanced oxygen consumption. If extrapolated to a typical marine environment, this indicates that alterations in the quality and reactivity of the organic components of the SML could be expected. This preliminary study shows the need for a more integrated effort to our understanding the impact of microplastics on SML functioning and marine biological processes. Full article
(This article belongs to the Special Issue Ocean-Atmosphere Interaction)
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