Using an Earth system model (ESM), we focus on two climate-relevant feedbacks, the biological pump and the phytoplankton light absorption feedback to study their relative importance for the climate system. Increasingly more marine ecosystem processes, particularly related to the food web, are included in models, but it is unclear whether a higher degree of complexity has a greater impact on the climate system compared to other climate relevant mechanisms that are often ignored, such as phytoplankton light absorption.State-of-the-art marine ecosystem models include several nutrients and different plankton functional types (PFTs) such as diatoms, coccolithophores, picoeukaryotes, and zooplankton (Laufkötter et al., 2015). These PFT-models are embedded within ESMs to study biogeochemical cycles (Ilyina et al., 2013;

Abstract. We investigate the ways in which marine biologically mediated heating increases the surface atmospheric temperature. While the effects of phytoplankton light absorption on the ocean have gained attention over the past years, the impact of this biogeophysical mechanism on the atmosphere is still unclear. Phytoplankton light absorption warms the surface of the ocean, which in turn affects the air–sea heat and CO2 exchanges. However, the contribution of air–sea heat versus CO2 fluxes in the phytoplankton-induced atmospheric warming has not been yet determined. Different so-called climate pathways are involved. We distinguish heat exchange, CO2 exchange, dissolved CO2, solubility of CO2 and sea-ice-covered area. To shed more light on this subject, we employ the EcoGEnIE Earth system model that includes a new light penetration scheme and isolate the effects of individual fluxes. Our results indicate that phytoplankton-induced changes in air–sea CO2 exchange warm the atmosphere by 0.71 ∘C due to higher greenhouse gas concentrations. The phytoplankton-induced changes in air–sea heat exchange cool the atmosphere by 0.02 ∘C due to a larger amount of outgoing longwave radiation. Overall, the enhanced air–sea CO2 exchange due to phytoplankton light absorption is the main driver in the biologically induced atmospheric heating.

Background Anthropogenic pressures on marine ecosystems have increased over the last 75 years and are expected to intensify in the future with potentially dramatic cascading consequences for human societies. It is therefore crucial to rebuild marine life-support systems and aim for future healthy ecosystems. Nowadays, there is a reasonable understanding of the impacts of human pressure on marine ecosystems; but no studies have drawn an integrative retrospective analysis of the marine research on the topic. A systematic consolidation of the literature is therefore needed to clearly describe the scientific knowledge clusters and gaps as well as to promote a new era of integrative marine science and management. We focus on the five direct anthropogenic drivers of biodiversity loss defined by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES): (1) climate change; (2) direct exploitation; (3) pollution; (4) biological invasions; and (5) sea-use change. Our systematic map’s regional focus lies on the North Sea, which is among the most impacted marine ecosystems around the globe. The goal of the present study is to produce the first comprehensive overview of how marine research on anthropogenic drivers in the North Sea has grown and changed over the past 75 years. Ultimately, this systematic map will highlight the most urgent challenges facing the North Sea research domain. Methods The search will be restricted to peer-reviewed articles, reviews, meta-analyses, book chapters, book reviews, proceeding papers and grey literature using the most relevant search engines for literature published between 1945 and 2020. All authors will participate in the adjustment of the search in order to consider all relevant studies analyzing the effect of the direct anthropogenic drivers on the North Sea marine ecosystem. The references will be screened for relevance according to a predefined set of eligibility/ineligibility criteria by a pool of six trained reviewers. At stage one, each abstract and title will be independently screened by two reviewers. At stage two, potentially relevant references will be screened in full text by two independent reviewers. Subsequently, we will extract a suite of descriptive meta-data and basic information of the relevant references using the SysRev platform. The systematic map database composed will provide the foundation for an interactive geographical evidence map. Moreover, we will summarize our findings with cross-validation plots, heat maps, descriptive statistics, and a publicly available narrative synthesis. The aim of our visualization tools is to ensure that our findings are easily understandable by a broad audience.

<p>The ocean is the largest carbon reservoir on Earth, and a major sink for the excess of CO<sub>2</sub> (anthropogenic carbon) emitted to the atmosphere by human activities. Having removed about a quater of these emissions since the beginning of the industrial era, ocean’s key role in climate is particularty outstanding in the North Atlantic (NA). A combination of physical and biological processes makes the NA a key-role region for the natural and anthropogenic carbon uptake and storage, and hence for the global carbon cycle. Traditionally, the seasonal carbon cycle has been assumed to respond to natural variability, unnafected by the ongoing anthropogenic increase of atmospheric CO<sub>2</sub>. Recent model projections, however, point otherwise, yet observational evidence to verify these predictions is still missing. Here we examine seasonal cycle in dissolved inorganic carbon (DIC) and its (surface-2000 dbar) transport, estimated using <em>in-situ</em> data and neural networks, across the OVIDE (GO-SHIP A25) section, from 1993 to 2021 at a monthly resolution. Our results highlight that changes in temperature, dissolved oxygen and ocean circulation are key components driving the seasonal DIC variability. DIC concentrations are higher in years with strong winter mixing regimes (which bring more nutrient-rich waters to the surface, favouring photosynthesis, and more (remineralized) carbon back to the surface). Seasonal DIC transport fluctuations are found significant compared to the mean (e.g. +/- 25% in the upper branch of the meridional overturning circulation), putting into relevance that caution is needed if assuming that single-cruise occupations are representative of the annual state. We also observe a yearly variant seasonal imbalance, with a significant reduction over the past two decades in the upper branch of the meridional overturning circulation. These results underscore the importance of considering intra-annual variability in the North Atlantic's carbon cycle when addressing climate change.</p> <div> <div> <div> </div> </div> <div> <div> </div> </div> <div> <div> </div> </div> </div>

<p>Since 1750s human industrial activities have emitted large amounts of CO<sub>2</sub> into the atmosphere, increasing the atmospheric CO<sub>2</sub> content to unprecedent levels. About a quarter of this exccess of carbon (namely anthropogenic carbon, C<sub>ant</sub>) is absorbed by the ocean, which acts as a major net C<sub>ant</sub> sink. Changes in the inorganic carbon chemistry of sea water due to the invasion of C<sub>ant</sub> - increasing (decreasing) concentration of hydrogen ions, H<sup>+</sup> (carbonate ions, CO<sub>3</sub><sup>2−</sup>) - are referred to as ocean acidification (OA). The North Atlantic is the oceanic region with the highest storage of C<sub>ant </sub>per area, closely linked to the Atlantic meridional overturning circulation and subpolar winter deep convection. As a result, it is also the main region where both upper-ocean C<sub>ant</sub> and fast OA signals are tranferred to deeper levels. Yet, it is still uncertain how much of this signal originates (locally) at these high latitudes or is conveyed (remotely) from the subtropics; or what are the driving mechanisms regulating its lateral vs vertical transfer at different temporal scales. Here we present the preliminary data and results of the CARING (Carbon irrigation in the Noth Atlantic by the gulf Stream) project to <em>i)</em> provide a contemporary assessment of the OA rates conveyed poleward by the Gulf Stream, and to <em>ii)</em> elucidate its role as far-field control to the North Atlantic OA. Our results of <em>i</em><em>n situ</em> pH data over the first 2000 dbar of the water-column, in combination with historical GLODAP data, show the pH decline to be the highest at the surface (subtropical waters down to</p>

Abstract. Marine biota and biogeophysical mechanisms, such as phytoplankton light absorption, have attracted increasing attention in recent climate studies. Under global warming, the impact of phytoplankton on the climate system is expected to change. Previous studies analyzed the impact of phytoplankton light absorption under prescribed future atmospheric CO2 concentrations. However, the role of this biogeophysical mechanism under freely-evolving atmospheric CO2 concentration and future CO2 emissions remains unknown. To shed light on this research gap, we perform simulations with the EcoGEnIE Earth system model and prescribe CO2 emissions out to 2500 following the four Extended Concentration Pathways (ECP) scenarios, which for practical purpose we call RCP scenarios. Under all RCP scenarios, our results indicate that phytopankton light absorption weakens the biological carbon pump while it increases the surface chlorophyll, the sea surface temperature, the atmospheric CO2 concentrations and the atmospheric temperature. Under the RCP2.6, RCP4.5 and RCP6.0 scenarios, the magnitude of changes due to phytoplankton light absorption is similar. However, under the RCP8.5 scenario, the changes in the climate system are less pronounced due to temperature limitation of phytoplankton concentration, highlighting a reduced effect of phytoplankton light absorption under strong warming. Additionally, this work highlights the major role of phytoplankton light absorption on the climate system, suggesting highly uncertain feedbacks on the carbon cycle with uncertainties that maybe in the range of those known from the land biota.

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