Sean D. Birkel

As climate variability increases, farmers and agricultural advisors must continually adapt to maintain viable food systems. To build efficacy for climate adaptation, we must understand and support the realities of individuals' adaptation processes. We argue here that we should in turn make visible the continuous and iterative adaptation processes of both farmers and advisors, and depart from previous short-term or practice-based approaches. This study investigates the adaptation processes of 18 fruit and vegetable growers and 18 professional advisors who participated in a Climate Adaptation Fellowship program in the Northeast US. Using longitudinal data from surveys and semi-structured interviews collected over three years, the study applies an integrated theoretical framework combining behavioral adaptation and a multi-stage adoption model to examine how adaptation unfolds during and after the program. Using a robust, mixed methods approach, we break down adaptation into action steps, and in doing so show the prevalence and diversity of actions occurring within a modification stage, where participants improve or tweak practices and systems over time. Case studies of participants illustrate how adaptation processes consisted of multiple, layered adoption processes. These processes were slow and iterative, as individuals explored, trialed, and evaluated results over multiple seasons. Influential factors included disruptive environmental stressors, personal values and experiences, as well as institutional and social support. Social interactions were salient in both early and later stages of adoption as participants drew on their connections to persist through challenging processes. These findings suggest that farmer and advisor adaptation processes are interdependent, reinforcing the value of joint learning and experimentation. This study highlights the need to move away from studying and recommending single prescriptive practices in the context-specific arena of climate adaptation, and instead focus on supporting advisors and farmers to work together on the sustained modification needed for effective adaptation in agricultural systems.

End of summer stratification and onset of ice‐on are shifting later across the mid‐latitudes, but the lake‐specific and climatic drivers of lake thermal structure in autumn remain unclear. We used high‐frequency water temperature data (2007–2021) from nine sub‐alpine (>600 m ASL) lakes in the Northeastern US to investigate the drivers and coherence of ecologically important autumn processes. The end of summer stratification was highly variable across lakes and mediated by DOC and lake depth. The timing of end of stratification affected the onset of continuous autumn mixing; however, mixing was decoupled from ice‐on. Ice‐on was highly coherent and driven by air temperature. Extreme weather events with high winds, heavy precipitation, and anomalous air temperatures drove early onset of mixing, re‐stratification events, and freeze‐melt events. The variability of thermal structure during autumn demonstrates that climate change will not uniformly shift the start and end of autumn season later in the year.

Wild blueberries in Maine, USA are facing threats from our changing climate. While summer climate variations have been affecting this important commercial crop directly, significant climate variations in other seasons also can be potentially detrimental to blueberry production. Therefore, we analyzed annual and seasonal climate trends (temperature, rainfall, snow cover) over the past 41 years (1980–2020) for seven Maine counties (Piscataquis, Washington, Hancock, Knox, Lincoln, Kennebec, York) with large wild blueberry areas. We found that, across all blueberry production fields (or “barrens”), historical temperatures increased significantly (p < 0.05) in the fall and winter followed by summer, but not in the spring. Additionally, precipitation increased slightly (0.5–1.2 mm/year) in the winter and fall, whereas no changes were found in the spring and summer. Furthermore, we found that historical temperatures were lower in Piscataquis (north-central) and Washington (north-east) counties, whereas in south-western counties (Hancock to York) experienced a relatively warmer climate. The rate of increasing temperature was comparatively slower in the warmer barrens located towards the south-west (Hancock to York). Moreover, the growing season lengthened towards the fall season consistently in all locations, whereas lengthening towards the spring was inconsistent. These findings inform the wild blueberry growers in different locations of Maine about the seasonal shifts occurring for their crop. This knowledge may assist with land management planning in order for the growers to prepare for future impacts.

This study compares temperature, precipitation, and other climate variables from six widely used climate reanalysis products to inform ice‐core climate proxy record calibration in the Altiplano region of the central Andes. The reanalyzes are the European Reanalysis version 5 (ERA5), European Reanalysis Interim, Modern‐Era Retrospective analysis for Research and Applications (MERRA2), Japanese 55‐year Reanalysis, Climate Forecast System Reanalysis and version 2 extension, and NCEP/NCAR Reanalysis version 1. These data products are validated against observations from automatic weather stations on the Quelccaya Ice Cap, Peru (5,650 m a.s.l) and Chacaltaya, Bolivia (5,238 m a.s.l), in addition to lower sites ranging in elevation 2,500–4,900 m a.s.l. Our results suggest that ERA5 provides the most robust overall depiction of temperature and precipitation across the study domain, and the data set is particularly useful for its back‐extension to 1950. However, MERRA2 produces lower precipitation error scores owing to a gaged‐based bias correction. An examination of ERA5 vertical atmospheric profiles for a latitudinal transect over Quelccaya shows considerable variability, including across major El Niño events, suggesting the need for caution when interpreting isotopic signatures in ice cores.

Globally, the changing and interacting effects of temperature and precipitation are anticipated to influence the fitness of specialty crops. Strawberry (Fragaria x ananassa) is an important crop in the Northeastern United States. In this study, four plausible precipitation scenarios were developed to be representative of current and future growing season precipitation patterns. Using a precipitation simulator, we tested these scenarios on potted-day-neutral strawberries. This study generated four primary results. (1) Though some treatments received different amounts of precipitation, little difference was observed in soil volumetric water content or temperature. Treatments designed to simulate future conditions were more likely to have higher nitrate-in-leachate (N-leachate) concentrations than those designed to simulate current conditions. (2) Neither total precipitation nor seasonable distribution were associated with foliar or root disease pressure. (3) While there was a slightly higher chance that photosynthesis would be higher in drier conditions, little difference was observed in the effects on chlorophyll concentration and no water stress was detected in any treatment. (4) Leaf biomass was likely more affected by total rather than seasonal distribution of precipitation, but the interaction between changing rainfall distribution and seasonal totals is likely to be an important driver of root biomass development in the future.

Lake morphometric, chemical, and watershed land-use attributes control lake phosphorus concentration. Lake depth, sediment chemical makeup, DOC, and watershed agricultural extent are the most important controlling variables.

The Atlantic multidecadal oscillation (AMO) is a 60–70 year pattern of sea-surface temperature (SST) variability in the North Atlantic commonly ascribed to internal ocean dynamics and changes in northward heat transport. Recent modeling studies, however, suggest that SSTs fluctuate primarily in response to major volcanic eruptions and changes in atmospheric circulation. Here, we utilize historical SST, atmospheric reanalysis, and stratospheric aerosol optical depth data to examine the basic evidence supporting a volcanic link. We find that cool intervals across the North Atlantic coincide with two distinct episodes of explosive volcanic activity (1880s–1920s and 1960s–1990s), where key eruptions include 1883 Krakatau, 1902 Santa María, 1912 Novarupta, 1963 Agung, 1982 El Chichón, and 1991 Pinatubo. Cool SST patterns develop in association with an increased prevalence of North Atlantic Oscillation (NAO)+ atmospheric patterns caused by stratospheric aerosol loading and a steepened poleward temperature gradient. NAO+ patterns promote wind-driven advection, evaporative cooling, and increased albedo from enhanced Saharan dust transport and anthropogenic aerosols. SSTs across the subpolar gyre are regulated by strength of low pressure near Iceland and the associated wind-driven advection of cold surface water from the Labrador Sea. This is contrary to an interpretation that subpolar SSTs are driven by changes in ocean overturning circulation. We also find that North Pacific and global mean SST declines can be readily associated with the same volcanic triggers that affect the North Atlantic. Thus, external forcing from volcanic aerosols appears to underpin multi-decade SST variability observed in the historical record.