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1. Exploring impacts of marine heatwaves: paternal heat exposure diminishes fertilization success in the purple sea urchin (Strongylocentrotus purpuratus)

   https://doi.org/10.1007/s00227-021-03915-x  

   Leach, Terence S. ; BuyanUrt, Buyanzaya ; Hofmann, Gretchen E. ( June 2021 , Marine Biology)

   Marine heatwaves (MHWs) are projected to increase in intensity and frequency over the coming decades, and it is imperative to assess the adaptive capacity of marine organisms to these extreme temperature events. Given the nature of MHWs to last days to weeks in a region, these events may have overarching impacts on phenological events like reproduction and development. Here, the role of adult thermal history and transgenerational plasticity may be an important pathway by which MHWs are transduced to impact community structure. In this study, we sought to explore the effects of paternal thermal history in the purple urchin,Strongylocentrotusmore »purpuratus, on a crucial aspect of reproduction, fertilization. Using ecologically relevant temperatures representative of both MHW events that occurred in 2014–2020 and non-MHW temperatures in our region of the California Large Marine Ecosystem, we conditioned maleS. purpuratusfor 28 days to either a high, MHW or a low, non-MHW temperature. Following the temperature acclimation of adults, sperm performance was tested for individual males by conducting fertilization success trials at varying temperatures and sperm concentrations. While sperm appeared robust to elevated temperature during fertilization, sperm produced by high-temperature-acclimated males had overall diminished performance as compared to those acclimated to non-MHW temperatures. These results suggest MHW events will have a negative impact on fertilization in situ forS. purpuratuspopulations. Furthermore, these results highlight the importance of considering both male and female environmental history in projections of reproduction under climate change scenarios.

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2. Carbon isotope minima in the South Atlantic during the last deglaciation: evaluating the influence of air-sea gas exchange

   https://doi.org/10.1088/1748-9326/ab126f  

   Lund, D. ; Hertzberg, J. ; Lacerra, M. ( May 2019 , Environmental Research Letters)

   Carbon isotope minima were a ubiquitous feature in the mid-depth (1.5–2.5 km) Atlantic during Heinrich Stadial 1 (HS1, 14.5–17.5 kyr BP) and the Younger Dryas (YD, 11.6–12.9 kyr BP), with the most likely driver being collapse of the Atlantic Meridional Overturning Circulation (AMOC). Negative carbon isotope anomalies also occurred throughout the surface ocean and atmosphere, but their timing relative to AMOC collapse and the underlying drivers have remained unclear. Here we evaluate the lead-lag relationship between AMOC variability and surface oceanδ¹³C signals using high resolution benthic and planktonic stable isotope records from two Brazil Margin cores (located at 1.8more »km and 2.1 km water depth). In each case, the decrease in benthicδ¹³C during HS1 leads planktonicδ¹³C by 800 ± 200 years. Because the records are based on the same samples, the relative timing is constrained by the core stratigraphy. Our results imply that AMOC collapse initiates a chain of events that propagates through the oceanic carbon cycle in less than 1 kyr. Direct comparison of planktonic foraminiferal and atmospheric records implies a portion of the surface oceanδ¹³C signal can be explained by temperature-dependent equilibration with a¹³C-depleted atmosphere, with the remainder due to biological productivity, input of carbon from the abyss, or reduced air-sea equilibration.

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3. Indian Ocean warming as a driver of the North Atlantic warming hole

   https://doi.org/10.1038/s41467-020-18522-5  

   Hu, Shineng ; Fedorov, Alexey V. ( September 2020 , Nature Communications)

   Over the past century, the subpolar North Atlantic experienced slight cooling or suppressed warming, relative to the background positive temperature trends, often dubbed the North Atlantic warming hole (NAWH). The causes of the NAWH remain under debate. Here we conduct coupled ocean-atmosphere simulations to demonstrate that enhanced Indian Ocean warming, another salient feature of global warming, could increase local rainfall and through teleconnections strengthen surface westerly winds south of Greenland, cooling the subpolar North Atlantic. In decades to follow however, this cooling effect would gradually vanish as the Indian Ocean warming acts to strengthen the Atlantic meridional overturning circulationmore »(AMOC). We argue that the historical NAWH can potentially be explained by such atmospheric mechanisms reliant on surface wind changes, while oceanic mechanisms related to AMOC changes become more important on longer timescales. Thus, explaining the North Atlantic temperature trends and particularly the NAWH requires considering both atmospheric and oceanic mechanisms.

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4. A numerical framework for simulating the atmospheric variability of supermicron marine biogenic ice nucleating particles

   https://doi.org/10.5194/acp-22-847-2022  

   Steinke, Isabelle ; DeMott, Paul J. ; Deane, Grant B. ; Hill, Thomas C. ; Maltrud, Mathew ; Raman, Aishwarya ; Burrows, Susannah M. ( January 2022 , Atmospheric Chemistry and Physics)

   Abstract. We present a framework for estimating concentrations of episodicallyelevated high-temperature marine ice nucleating particles (INPs) in the seasurface microlayer and their subsequent emission into the atmosphericboundary layer. These episodic INPs have been observed in multipleship-based and coastal field campaigns, but the processes controlling theirocean concentrations and transfer to the atmosphere are not yet fullyunderstood. We use a combination of empirical constraints and simulationoutputs from an Earth system model to explore different hypotheses forexplaining the variability of INP concentrations, and the occurrence ofepisodic INPs, in the marine atmosphere. In our calculations, we examine the following two proposed oceanic sources of high-temperaturemore »INPs: heterotrophic bacteria and marine biopolymer aggregates (MBPAs). Furthermore, we assume that the emission of these INPs is determined by the production of supermicron sea spray aerosol formed from jet drops, with an entrainment probability that is described by Poisson statistics. The concentration of jet drops is derived from the number concentration of supermicron sea spray aerosol calculated from model runs. We then derive the resulting number concentrations of marine high-temperature INPs (at 253 K) in the atmospheric boundary layer and compare their variability to atmospheric observations of INP variability. Specifically, we compare against concentrations of episodically occurring high-temperature INPs observed during field campaigns in the Southern Ocean, the Equatorial Pacific, and the North Atlantic. In this case study, we evaluate our framework at 253 K because reliable observational data at this temperature are available across three different ocean regions, but suitable data are sparse at higher temperatures. We find that heterotrophic bacteria and MBPAs acting as INPs provide only apartial explanation for the observed high INP concentrations. We note,however, that there are still substantial knowledge gaps, particularlyconcerning the identity of the oceanic INPs contributing most frequently toepisodic high-temperature INPs, their specific ice nucleation activity, andthe enrichment of their concentrations during the sea–air transfer process. Therefore, targeted measurements investigating the composition of these marine INPs and drivers for their emissions are needed, ideally incombination with modeling studies focused on the potential cloud impacts ofthese high-temperature INPs.« less
5. Oceanic eddy-induced modifications to air–sea heat and CO2 fluxes in the Brazil-Malvinas Confluence

   https://doi.org/10.1038/s41598-021-89985-9  

   Pezzi, Luciano P. ; de Souza, Ronald B. ; Santini, Marcelo F. ; Miller, Arthur J. ; Carvalho, Jonas T. ; Parise, Claudia K. ; Quadro, Mario F. ; Rosa, Eliana B. ; Justino, Flavio ; Sutil, Ueslei A. ; et al ( May 2021 , Scientific Reports)

   Sea surface temperature (SST) anomalies caused by a warm core eddy (WCE) in the Southwestern Atlantic Ocean (SWA) rendered a crucial influence on modifying the marine atmospheric boundary layer (MABL). During the first cruise to support the Antarctic Modeling and Observation System (ATMOS) project, a WCE that was shed from the Brazil Current was sampled. Apart from traditional meteorological measurements, we used the Eddy Covariance method to directly measure the ocean–atmosphere sensible heat, latent heat, momentum, and carbon dioxide (CO₂) fluxes. The mechanisms of pressure adjustment and vertical mixing that can make the MABL unstable were both identified. Themore »WCE also acted to increase the surface winds and heat fluxes from the ocean to the atmosphere. Oceanic regions at middle and high latitudes are expected to absorb atmospheric CO₂, and are thereby considered as sinks, due to their cold waters. Instead, the presence of this WCE in midlatitudes, surrounded by predominantly cold waters, caused the ocean to locally act as a CO₂source. The contribution to the atmosphere was estimated as 0.3 ± 0.04 mmol m⁻²day⁻¹, averaged over the sampling period. The CO₂transfer velocity coefficient (K) was determined using a quadratic fit and showed an adequate representation of ocean–atmosphere fluxes. The ocean–atmosphere CO₂, momentum, and heat fluxes were each closely correlated with the SST. The increase of SST inside the WCE clearly resulted in larger magnitudes of all of the ocean–atmosphere fluxes studied here. This study adds to our understanding of how oceanic mesoscale structures, such as this WCE, affect the overlying atmosphere.

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