Recent (1980 to 2015) Trends and Variability in Daily‐to‐Interannual Soluble Iron Deposition from Dust, Fire, and Anthropogenic Sources

Abstract

The iron cycle is a key component of the Earth system. Yet how variable the atmospheric flux of soluble (bioaccessible) iron into oceans is, and how this variability is modulated by human activity and a changing climate, is not well known. For the first time, we characterize Satellite Era (1980 to 2015) daily‐to‐interannual modeled soluble iron emission and deposition variability from both pyrogenic (fires and anthropogenic combustion) and dust sources. Statistically significant emission trends exist: dust iron decreases, fire iron slightly increases, and anthropogenic iron increases. A strong temporal variability in deposition to ocean basins is found, and, for most regions, dust iron dominates the absolute deposition magnitude, fire iron is an important contributor to temporal variability, and anthropogenic iron imposes a significant increasing trend. Quantifying soluble iron daily‐to‐interannual deposition variability from all major iron sources, not only dust, will advance quantification of changes in marine biogeochemistry in response to the continuing human perturbation to the Earth System.

Impact of intensifying nitrogen limitation on ocean net primary production is fingerprinted by nitrogen isotopes

“…1g). Although the response of hypoxic zones, and hence nitrogen sinks, to climate change is subject to considerable uncertainty 50 , the shift towards accumulation is consistent with previous modelling 3 and may be reinforced by including currently unrepresented processes, such as the stimulation of nitrogen fixation by increasing pCO 2 46 and anthropogenic iron deposition 51 . Net accumulation of bioavailable nitrogen in the twenty-first century, if realized, may mitigate or even counteract the multi-centennial declines in NPP that are projected as a result of nutrient trapping in the deep ocean 13 and potentially represents an important self-stabilizing mechanism for ocean productivity on multi-centennial timescales.…”

The Regional Importance of Oxygen Demand and Supply for Historical Ocean Oxygen Trends

“…Misrepresented physical mechanisms affect how O 2 is supplied to the mesopelagic and include poorly resolved mesoscale processes due to coarse model resolution (Lévy et al., 2021; Stewart et al., 2017) and/or inaccurate atmospheric phasing in anthropogenically forced (i.e., greenhouse gases, aerosols, land use, and ozone; Eyring et al., 2016) scenarios (Breitburg et al., 2018; Duteil et al., 2018; Frölicher et al., 2009). Meanwhile, many biogeochemical mechanisms control O 2 demand beneath the euphotic zone and include (but are not limited to) fertilization of primary producers by CO 2 (Andrews et al., 2017) or external nutrients (Breitburg et al., 2018; Duce et al., 2008; Hamilton et al., 2020; Ito et al., 2016), ballasting of organic matter (Aumont et al., 2017), stoichiometric variations (Moreno et al., 2020), and vertical zooplankton migrations (Archibald et al., 2019), all of which, if represented, are represented differently by ESMs.…”

The Summer 2019–2020 Wildfires in East Coast Australia and Their Impacts on Air Quality and Health in New South Wales, Australia

“…Deposition of fire pollutants, such as Fe, on water body surfaces like the ocean also stimulates the growth of phytoplankton. After dust deposition, pyrogenic (fires and anthropogenic combustion) Fe is the second largest source of Fe deposition on the surface of the ocean and is a significant contributor to daily, seasonal and interannual variability of Fe in the ocean basins [ 15 ].…”