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Population growth, arable land and fresh water limits, and climate change have profound implications for the ability of agriculture to meet this century's demands for food, feed, fiber, and fuel while reducing the environmental impact of their production. Success depends on the acceptance and use of contemporary molecular techniques, as well as the increasing development of farming systems that use saline water and integrate nutrient flows.

Arctic warming under increased CO2 peaks in winter, but is influenced by summer forcing via seasonal ocean heat storage. Yet changes in atmospheric heat transport into the Arctic have mainly been investigated in the annual mean or winter, with limited focus on other seasons. We investigate the full seasonal cycle of poleward heat transport modeled with increased CO2 or with individually applied Arctic sea‐ice loss and global sea‐surface warming. We find that a winter reduction in dry heat transport is driven by Arctic sea‐ice loss and warming, while a summer increase in moist heat transport is driven by sub‐Arctic warming and moistening. Intermodel spread in Arctic warming controls spread in seasonal poleward heat transport. These seasonal changes and their intermodel spread are well‐captured by down‐gradient diffusive heat transport. While changes in moist and dry heat transport compensate in the annual‐mean, their opposite seasonality may support non‐compensating effects on Arctic warming. Plain Language Summary: The Arctic is warming much faster than the rest of the planet in response to rising greenhouse gas concentrations. Because Arctic warming peaks in winter, many studies have focused on the wintertime processes amplifying Arctic warming. However, others have found that summer atmospheric heating also contributes to winter warming by melting sea ice and storing heat in the ocean until it is released to the atmosphere in winter. Here we study changes in all seasons for one source of atmospheric heating in the Arctic—atmospheric heat transport from lower latitudes. Using climate model simulations, we find that heat and moisture are transported away from the regions that warm and moisten the most in response to rising greenhouse gas concentrations. The Arctic warms more than lower latitudes in winter, which reduces heat transport to the Arctic in winter. Atmospheric moisture increases most in late summer at lower latitudes, driving increased moisture transport in late summer from lower latitudes to the Arctic. We suggest that changes in heat and moisture transport may impact Arctic warming differently due to their opposite seasonality: by producing a larger change in surface solar absorption, summer changes in moisture transport may outweigh winter changes in heat transport. Key Points: Sea‐ice loss reduces dry heat transport to the Arctic in winter; sub‐Arctic warming increases latent heat transport to the Arctic in summerIntermodel spread in Arctic warming controls intermodel spread in seasonal heat transport changesThe seasonal pattern of poleward heat transport change is well‐captured by down‐gradient diffusion of temperature and moisture anomalies [ABSTRACT FROM AUTHOR]

The impact of global orography on Northern Hemisphere wintertime climate is revisited using the Whole Atmosphere Community Climate Model, version 6 (WACCM6). A suite of experiments explores the roles of both resolved orography and the parameterized effects of unresolved orographic drag (hereafter parameterized orography), including gravity waves and boundary layer turbulence. Including orography reduces the extratropical tropospheric and stratospheric zonal mean zonal wind U ¯ by up to 80%; this is substantially greater than previous estimates. Ultimately, parameterized orography accounts for 60%–80% of this reduction; however, away from the surface most of the forcing of U ¯ by parameterized orography is accomplished by resolved planetary waves. We propose that a catalytic wave–mean-flow positive feedback in the stratosphere makes the stratospheric flow particularly sensitive to parameterized orography. Orography and land–sea contrast contribute approximately equally to the strength of the midlatitude stationary waves in the free troposphere, although orography is the dominant cause of the strength of the Siberian high and Aleutian low at the surface and of the position of the Icelandic low. We argue that precisely quantifying the role of orography on the observed stationary waves is an almost intractable problem, and in particular should not be approached with linear stationary wave models in which U ¯ is prescribed. We show that orography has less impact on stationary waves, and therefore on U ¯ , on a backward-rotating Earth. Last, we show that atmospheric meridional heat transport shows remarkable constancy across our simulations, despite vastly different climates and stationary wave strengths. [ABSTRACT FROM AUTHOR]

Arctic warming under increased CO2 peaks in winter, but is influenced by summer forcing via seasonal ocean heat storage. Yet changes in atmospheric heat transport into the Arctic have mainly been investigated in the annual mean or winter, with limited focus on other seasons. We investigate the full seasonal cycle of poleward heat transport modeled with increased CO2 or with individually applied Arctic sea‐ice loss and global sea‐surface warming. We find that a winter reduction in dry heat transport is driven by Arctic sea‐ice loss and warming, while a summer increase in moist heat transport is driven by sub‐Arctic warming and moistening. Intermodel spread in Arctic warming controls spread in seasonal poleward heat transport. These seasonal changes and their intermodel spread are well‐captured by down‐gradient diffusive heat transport. While changes in moist and dry heat transport compensate in the annual‐mean, their opposite seasonality may support non‐compensating effects on Arctic warming. Plain Language Summary: The Arctic is warming much faster than the rest of the planet in response to rising greenhouse gas concentrations. Because Arctic warming peaks in winter, many studies have focused on the wintertime processes amplifying Arctic warming. However, others have found that summer atmospheric heating also contributes to winter warming by melting sea ice and storing heat in the ocean until it is released to the atmosphere in winter. Here we study changes in all seasons for one source of atmospheric heating in the Arctic—atmospheric heat transport from lower latitudes. Using climate model simulations, we find that heat and moisture are transported away from the regions that warm and moisten the most in response to rising greenhouse gas concentrations. The Arctic warms more than lower latitudes in winter, which reduces heat transport to the Arctic in winter. Atmospheric moisture increases most in late summer at lower latitudes, driving increased moisture transport in late summer from lower latitudes to the Arctic. We suggest that changes in heat and moisture transport may impact Arctic warming differently due to their opposite seasonality: by producing a larger change in surface solar absorption, summer changes in moisture transport may outweigh winter changes in heat transport. Key Points: Sea‐ice loss reduces dry heat transport to the Arctic in winter; sub‐Arctic warming increases latent heat transport to the Arctic in summerIntermodel spread in Arctic warming controls intermodel spread in seasonal heat transport changesThe seasonal pattern of poleward heat transport change is well‐captured by down‐gradient diffusion of temperature and moisture anomalies [ABSTRACT FROM AUTHOR]