This paper presents a global model‐based country‐scale quantification of urban N and P mass flows from humans, animals, and industries and their waste N and P discharges to surface water and urban ...waste recycling in agriculture. Agricultural recycling was practiced commonly in early twentieth century Europe, Asia, and North America. During the twentieth century, global urban discharge to surface water increased ~3.5‐fold to 7.7 Tg yr‐1 for N and ~4.5‐fold to 1.0 Tg yr‐1 for P; the major part of this increase occurred between 1950 and 2000. Between 1900 and ~1940, industrial N and P flows dominated global surface water N and P loadings from urban areas; since ~1940, human wastes are the major source of urban nutrient discharge to both surface water and agricultural recycling. During the period 1900–2000, total global recycling of urban nutrients in agriculture increased from 0.4 to 0.6 Tg N yr‐1 and from 0.07 to 0.08 Tg P yr‐1. A large number of factors (the major ones related to food consumption, urban population, sewer connection, and industrial emissions) contribute to the uncertainty of −18% to +42% for N and −21% to +45% for P around the calculated surface water loading estimate for 2000.
Key Points
A global model was made to inventory urban 20th century nutrient flows
Global surface water discharge increased ~3.5‐fold for N and ~4.5‐fold for P
At present human excreta and detergents are the major urban nutrient sources
The ocean carbon cycle is a key player in the climate system through its role in regulating the atmospheric carbon dioxide concentration and other processes that alter the Earth's radiative balance. ...In the second version of the Norwegian Earth System Model (NorESM2), the oceanic carbon cycle component has gone through numerous updates that include, amongst others, improved process representations, increased interactions with the atmosphere, and additional new tracers. Oceanic dimethyl sulfide (DMS) is now prognostically simulated and its fluxes are directly coupled with the atmospheric component, leading to a direct feedback to the climate. Atmospheric nitrogen deposition and additional riverine inputs of other biogeochemical tracers have recently been included in the model. The implementation of new tracers such as “preformed” and “natural” tracers enables a separation of physical from biogeochemical drivers as well as of internal from external forcings and hence a better diagnostic of the simulated biogeochemical variability. Carbon isotope tracers have been implemented and will be relevant for studying long-term past climate changes. Here, we describe these new model implementations and present an evaluation of the model's performance in simulating the observed climatological states of water-column biogeochemistry and in simulating transient evolution over the historical period. Compared to its predecessor NorESM1, the new model's performance has improved considerably in many aspects. In the interior, the observed spatial patterns of nutrients, oxygen, and carbon chemistry are better reproduced, reducing the overall model biases. A new set of ecosystem parameters and improved mixed layer dynamics improve the representation of upper-ocean processes (biological production and air–sea CO2 fluxes) at seasonal timescale. Transient warming and air–sea CO2 fluxes over the historical period are also in good agreement with observation-based estimates. NorESM2 participates in the Coupled Model Intercomparison Project phase 6 (CMIP6) through DECK (Diagnostic, Evaluation and Characterization of Klima) and several endorsed MIP simulations.
Ocean temperature and dissolved oxygen shape marine habitats in an interplay with species' physiological characteristics. Therefore, the observed and projected warming and deoxygenation of the ...world's oceans in the 21st century may strongly affect species' habitats. Here, we implement an extended version of the Aerobic Growth Index (AGI), which quantifies whether a viable population of a species can be sustained in a particular location. We assess the impact of projected deoxygenation and warming on the contemporary habitat of 47 representative marine species covering the epipelagic, mesopelagic, and demersal realms. AGI is calculated for these species for the historical period and into the 21st century using bias-corrected environmental data from six comprehensive Earth system models. While habitat viability decreases nearly everywhere with global warming, the impact of this decrease is strongly species dependent. Most species lose less than 5 % of their contemporary habitat volume at 2 ∘C of global warming relative to preindustrial levels, although some individual species are projected to incur losses 2–3 times greater than that. We find that the in-habitat spatiotemporal variability of O2 and temperature (and hence AGI) provides a quantifiable measure of a species' vulnerability to change. In the event of potential large habitat losses (over 5 %), species vulnerability is the most important indicator. Vulnerability is more critical than changes in habitat viability, temperature, or pO2 levels. Loss of contemporary habitat is for most epipelagic species driven by the warming of ocean water and is therefore elevated with increased levels of global warming. In the mesopelagic and demersal realms, habitat loss is also affected by pO2 decrease for some species. Our analysis is constrained by the uncertainties involved in species-specific critical thresholds, which we quantify; by data limitations on 3D species distributions; and by high uncertainty in model O2 projections in equatorial regions. A focus on these topics in future research will strengthen our confidence in assessing climate-change-driven losses of contemporary habitats across the global oceans.
Model simulations of the Last Glacial Maximum (LGM;
∼ 21 000 years before present) can aid the interpretation of
proxy records, can help to gain an improved mechanistic understanding of the LGM
...climate system, and are valuable for the evaluation of model performance in
a different climate state. Ocean-ice only model configurations forced by
prescribed atmospheric data (referred to as “forced ocean models”)
drastically reduce the computational cost of palaeoclimate modelling
compared to fully coupled model frameworks. While feedbacks between the
atmosphere and ocean and sea-ice compartments of the Earth system are not
present in such model configurations, many scientific questions can be
addressed with models of this type. Our dataset supports simulations of the
LGM in a forced ocean model set-up while still taking advantage of the
complexity of fully coupled model set-ups. The data presented here are
derived from fully coupled palaeoclimate simulations of the Palaeoclimate
Modelling Intercomparison Project phase 3 (PMIP3). The data are publicly
accessible at the National Infrastructure for Research Data (NIRD) Research Data Archive at
https://doi.org/10.11582/2020.00052 (Morée and Schwinger, 2020). They
consist of 2-D anomaly forcing fields suitable for use in ocean models that
employ a bulk forcing approach and are optimized for use with CORE forcing
fields. The data include specific humidity, downwelling long-wave and
short-wave radiation, precipitation, wind (v and u components), temperature,
and sea surface salinity (SSS). All fields are provided as climatological
mean anomalies between LGM and pre-industrial (PI) simulations. These anomaly
data can therefore be added to any pre-industrial ocean forcing dataset in
order to obtain forcing fields representative of LGM conditions as simulated
by PMIP3 models. Furthermore, the dataset can be easily updated to reflect
results from upcoming and future palaeo-model intercomparison activities.
δ13C, the standardised 13C / 12C ratio expressed in per mille, is a widely used ocean tracer to study changes in ocean circulation, water mass ventilation, atmospheric pCO2, and the biological carbon ...pump on timescales ranging from decades to tens of millions of years. δ13C data derived from ocean sediment core analysis provide information on δ13C of dissolved inorganic carbon and the vertical δ13C gradient (i.e. Δδ13C) in past oceans. In order to correctly interpretδ13C and Δδ13C variations, a good understanding is needed of the influence from ocean circulation, air–sea gas exchange and biological productivity on these variations. The Southern Ocean is a key region for these processes, and we show here that Δδ13C in all ocean basins is sensitive to changes in the biogeochemical state of the Southern Ocean. We conduct a set of idealised sensitivity experiments with the ocean biogeochemistry general circulation model HAMOCC2s to explore the effect of biogeochemical state changes of the Southern and Global Ocean on atmospheric δ13C,pCO2, and marine δ13C and Δδ13C. The experiments cover changes in air–sea gas exchange rates, particulate organic carbon sinking rates, sea ice cover, and nutrient uptake efficiency in an unchanged ocean circulation field. Our experiments show that global mean Δδ13C varies by up to about ±0.35 ‰ around the pre-industrial model reference (1.2 ‰) in response to biogeochemical change. The amplitude of this sensitivity can be larger at smaller scales, as seen from a maximum sensitivity of about -0.6 ‰ on ocean basin scale. The ocean's oldest water (North Pacific) responds most to biological changes, the young deep water (North Atlantic) responds strongly to air–sea gas exchange changes, and the vertically well-mixed water (SO) has a low or even reversedΔδ13C sensitivity compared to the other basins. This local Δδ13C sensitivity depends on the local thermodynamic disequilibrium and the Δδ13C sensitivity to local POC export production changes. The direction of both glacial (intensification of Δδ13C) and interglacial (weakening ofΔδ13C) Δδ13C change matches the direction of the sensitivity of biogeochemical processes associated with these periods. This supports the idea that biogeochemistry likely explains part of the reconstructed variations in Δδ13C, in addition to changes in ocean circulation.
δ13C, the standardised 13C ∕ 12C ratio expressed in per mille, is a widely used ocean tracer to study changes in ocean circulation, water mass ventilation, atmospheric pCO2, and the biological carbon ...pump on timescales ranging from decades to tens of millions of years. δ13C data derived from ocean sediment core analysis provide information on δ13C of dissolved inorganic carbon and the vertical δ13C gradient (i.e. Δδ13C) in past oceans. In order to correctly interpret δ13C and Δδ13C variations, a good understanding is needed of the influence from ocean circulation, air–sea gas exchange and biological productivity on these variations. The Southern Ocean is a key region for these processes, and we show here that Δδ13C in all ocean basins is sensitive to changes in the biogeochemical state of the Southern Ocean. We conduct a set of idealised sensitivity experiments with the ocean biogeochemistry general circulation model HAMOCC2s to explore the effect of biogeochemical state changes of the Southern and Global Ocean on atmospheric δ13C, pCO2, and marine δ13C and Δδ13C. The experiments cover changes in air–sea gas exchange rates, particulate organic carbon sinking rates, sea ice cover, and nutrient uptake efficiency in an unchanged ocean circulation field. Our experiments show that global mean Δδ13C varies by up to about ±0.35 ‰ around the pre-industrial model reference (1.2 ‰) in response to biogeochemical change. The amplitude of this sensitivity can be larger at smaller scales, as seen from a maximum sensitivity of about −0.6 ‰ on ocean basin scale. The ocean's oldest water (North Pacific) responds most to biological changes, the young deep water (North Atlantic) responds strongly to air–sea gas exchange changes, and the vertically well-mixed water (SO) has a low or even reversed Δδ13C sensitivity compared to the other basins. This local Δδ13C sensitivity depends on the local thermodynamic disequilibrium and the Δδ13C sensitivity to local POC export production changes. The direction of both glacial (intensification of Δδ13C) and interglacial (weakening of Δδ13C) Δδ13C change matches the direction of the sensitivity of biogeochemical processes associated with these periods. This supports the idea that biogeochemistry likely explains part of the reconstructed variations in Δδ13C, in addition to changes in ocean circulation.
delta.sup.13 C, the standardised .sup.13 C / .sup.12 C ratio expressed in per mille, is a widely used ocean tracer to study changes in ocean circulation, water mass ventilation, atmospheric ...pCO.sub.2, and the biological carbon pump on timescales ranging from decades to tens of millions of years. delta.sup.13 C data derived from ocean sediment core analysis provide information on delta.sup.13 C of dissolved inorganic carbon and the vertical delta.sup.13 C gradient (i.e. Îdelta.sup.13 C) in past oceans. In order to correctly interpret delta.sup.13 C and Îdelta.sup.13 C variations, a good understanding is needed of the influence from ocean circulation, air-sea gas exchange and biological productivity on these variations. The Southern Ocean is a key region for these processes, and we show here that Îdelta.sup.13 C in all ocean basins is sensitive to changes in the biogeochemical state of the Southern Ocean. We conduct a set of idealised sensitivity experiments with the ocean biogeochemistry general circulation model HAMOCC2s to explore the effect of biogeochemical state changes of the Southern and Global Ocean on atmospheric delta.sup.13 C, pCO.sub.2, and marine delta.sup.13 C and Îdelta.sup.13 C. The experiments cover changes in air-sea gas exchange rates, particulate organic carbon sinking rates, sea ice cover, and nutrient uptake efficiency in an unchanged ocean circulation field. Our experiments show that global mean Îdelta.sup.13 C varies by up to about ±0.35 0/00 around the pre-industrial model reference (1.2 0/00) in response to biogeochemical change. The amplitude of this sensitivity can be larger at smaller scales, as seen from a maximum sensitivity of about -0.6 0/00 on ocean basin scale. The ocean's oldest water (North Pacific) responds most to biological changes, the young deep water (North Atlantic) responds strongly to air-sea gas exchange changes, and the vertically well-mixed water (SO) has a low or even reversed Îdelta.sup.13 C sensitivity compared to the other basins. This local Îdelta.sup.13 C sensitivity depends on the local thermodynamic disequilibrium and the Îdelta.sup.13 C sensitivity to local POC export production changes. The direction of both glacial (intensification of Îdelta.sup.13 C) and interglacial (weakening of Îdelta.sup.13 C) Îdelta.sup.13 C change matches the direction of the sensitivity of biogeochemical processes associated with these periods. This supports the idea that biogeochemistry likely explains part of the reconstructed variations in Îdelta.sup.13 C, in addition to changes in ocean circulation.
Abstract
The dominant pacing of glacial‐interglacial cycles in deep‐ocean δ
18
O records changed substantially during the Mid‐Pleistocene Transition. The precessional cycle (∼23 ky) is absent during ...the Early Pleistocene, which we show can be explained by cancellation of the hemispherically antiphased precessional cycle in the Early Pleistocene interior ocean. Such cancellation develops due to mixing of North Atlantic and Southern Ocean δ
18
O signals at depth, and shows characteristic spatial patterns. We explore the cancellation potential for different North Atlantic and Southern Ocean deep‐water source δ
18
O values using a tracer transport ocean model. Cancellation of precession occurs for all signal strengths and is widespread for a signal strength typical for the Early Pleistocene. Early Pleistocene precessional power is therefore likely incompletely archived in deep‐sea δ
18
O records, concealing the true periodicity of the glacial cycles in the two hemispheres.
Plain Language Summary
δ
18
O records from deep‐sea sediments show a pronounced difference in periodicity between the Early (∼2‐1 Million years ago) and Late (∼1‐0 Million years ago) Pleistocene—the Mid‐Pleistocene Transition (MPT). Representing changes in ice volume and temperature, these δ
18
O records are an important source for our understanding of long‐term climate variability. A central conclusion based on these δ
18
O records is that glacial‐interglacial cycles considerably changed their rhythm during the Mid‐Pleistocene. Curiously, the ∼23,000‐year (precessional) cycle of insolation is absent in Early Pleistocene δ
18
O records—despite its presence in insolation forcing to the ice sheets. Climate feedbacks involving (sea) ice, geological processes and carbon cycling may have contributed to the MPT. We, however, show that the absence of an Early Pleistocene precession signal in deep‐sea δ
18
O records could be the result of destructive interference in the deep ocean, caused by the antiphasing of the precessional cycle between the North Atlantic and Southern Ocean deep‐water sources. We explore the potential for cancellation with an ocean model and show that interference can indeed cause widespread cancellation, particularly in the Early Pleistocene. We, therefore, conclude that the δ
18
O incompletely archives climatic cycles, challenging our understanding of long‐term climate variability.
Key Points
Glacial‐interglacial cycles can be incompletely recorded in the ocean due to cancellation of hemispherically antiphased signals
Precessional cancellation develops due to mixing of North Atlantic and Southern Ocean δ
18
O signals at depth
Model experiments show widespread precessional cancellation for the Early Pleistocene
The dominant pacing of glacial‐interglacial cycles in deep‐ocean δ18O records changed substantially during the Mid‐Pleistocene Transition. The precessional cycle (∼23 ky) is absent during the Early ...Pleistocene, which we show can be explained by cancellation of the hemispherically antiphased precessional cycle in the Early Pleistocene interior ocean. Such cancellation develops due to mixing of North Atlantic and Southern Ocean δ18O signals at depth, and shows characteristic spatial patterns. We explore the cancellation potential for different North Atlantic and Southern Ocean deep‐water source δ18O values using a tracer transport ocean model. Cancellation of precession occurs for all signal strengths and is widespread for a signal strength typical for the Early Pleistocene. Early Pleistocene precessional power is therefore likely incompletely archived in deep‐sea δ18O records, concealing the true periodicity of the glacial cycles in the two hemispheres.
Plain Language Summary
δ18O records from deep‐sea sediments show a pronounced difference in periodicity between the Early (∼2‐1 Million years ago) and Late (∼1‐0 Million years ago) Pleistocene—the Mid‐Pleistocene Transition (MPT). Representing changes in ice volume and temperature, these δ18O records are an important source for our understanding of long‐term climate variability. A central conclusion based on these δ18O records is that glacial‐interglacial cycles considerably changed their rhythm during the Mid‐Pleistocene. Curiously, the ∼23,000‐year (precessional) cycle of insolation is absent in Early Pleistocene δ18O records—despite its presence in insolation forcing to the ice sheets. Climate feedbacks involving (sea) ice, geological processes and carbon cycling may have contributed to the MPT. We, however, show that the absence of an Early Pleistocene precession signal in deep‐sea δ18O records could be the result of destructive interference in the deep ocean, caused by the antiphasing of the precessional cycle between the North Atlantic and Southern Ocean deep‐water sources. We explore the potential for cancellation with an ocean model and show that interference can indeed cause widespread cancellation, particularly in the Early Pleistocene. We, therefore, conclude that the δ18O incompletely archives climatic cycles, challenging our understanding of long‐term climate variability.
Key Points
Glacial‐interglacial cycles can be incompletely recorded in the ocean due to cancellation of hemispherically antiphased signals
Precessional cancellation develops due to mixing of North Atlantic and Southern Ocean δ18O signals at depth
Model experiments show widespread precessional cancellation for the Early Pleistocene
White-nose syndrome (WNS) caused by the pathogenic fungus Pseudogymnoascus destructans is decimating the populations of several hibernating North American bat species. Little is known about the ...molecular interplay between pathogen and host in this disease. Fluorescence microscopy ambient ionization mass spectrometry was used to generate metabolic profiles from the wings of both healthy and diseased bats of the genus Myotis. Fungal siderophores, molecules that scavenge iron from the environment, were detected on the wings of bats with WNS, but not on healthy bats. This work is among the first examples in which microbial molecules are directly detected from an infected host and highlights the ability of atmospheric ionization methodologies to provide direct molecular insight into infection.
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