Kuskokwim River Research Articles

Slaviq

Slaviq is an Orthodox Native Alaskan celebration beginning on the feast of the Nativity of Christ, marked by indigenous people throughout Alaska. It is especially celebrated among the Yup’ik people in mainland southwestern Alaska in the Kuskokwim River delta region. Slaviq or “starring” lasts from three to ten days involving processions by the congregation, and especially the choir, from the church to homes of villagers wishing to host the celebration. At each host’s home a short prayer service is sung accompanied by the spinning of the Christmas star affixed to a pole held generally by young men. This is followed by a short sermon delivered by the priest or even a reader, and then by the singing of Orthodox liturgical hymns in praise of the Nativity of Christ, Ukrainian koliady and folk songs from the Carpathian Mountains describing the feast day, and American Christmas carols. This paraliturgical celebration is followed by the distribution of candy and gifts by the hosts to all the guests, and a festive meal for more senior members of the community who are present. Traditionally, this meal consists of dried fish, often salmon, fermented foods, and moose and reindeer soup followed by akutaq, a dessert containing berries mixed with animal fat. This study analyzes the historical and contemporary practice of celebrating Slaviq, viewing it as a cultural adaptation and expression of the indigenous Yup’ik ethical code enacted within an innovative Orthodox practice.

In-season monitoring of harvest and effort from a large-scale subsistence salmon fishery in western Alaska

In-season management of salmon harvest requires real-time data. Specifically, following a brief period of open fishing, knowledge of harvest outcomes is useful when deciding the nature of subsequent fishing periods. This in-season management strategy is relatively new to the lower Kuskokwim River of western Alaska, where depressed salmon runs have caused restrictions to the subsistence fishery. We have developed an in-season monitoring program to rapidly inform managers about fishery outcomes from short-duration (6-24 hours) fishery openings. Completed trip information and one or more aerial surveys are combined to estimate daily effort and harvest from drift gillnet fishers spanning 11 communities and ~130 river kilometers. We present a re-analysis of the 40 monitored openers in June-July 2016-2023, and validate harvest estimates of Chinook, chum, and sockeye salmon by comparing them to post-season estimates derived from an independent long-term monitoring program. Our results indicate that the program has produced estimates of sufficient quality to inform in-season managers, although it will likely need alterations to be successful in years with less restricted fishing.

Watershed features shape spatial patterns of fish tissue mercury in a boreal river network

Freshwater mercury (Hg) contamination is a widespread environmental concern but how proximate sources and downstream transport shape Hg spatial patterns in riverine food webs is poorly understood. We measured total Hg (THg) in slimy sculpin (Cottus cognatus) across the Kuskokwim River, a large boreal river in western Alaska and home to subsistence fishing communities which rely on fish for primary nutrition. We used spatial stream network models (SSNMs) to quantify watershed and instream conditions influencing sculpin THg. Spatial covariates for local watershed geology and slope accounted for 55 % of observed variation in sculpin THg and evidence for downstream transport of Hg in sculpins was weak. Empirical semivariograms indicated these spatial covariates accounted for most spatial autocorrelation in observed THg. Watershed geology and slope explained up to 70 % of sculpin THg variation when SSNMs accounted for instream spatial dependence. Our results provide network-wide predictions for fish tissue THg based largely on publicly available geospatial data and open-source software for SSNMs, and demonstrate how these emerging models can be used to understand contaminant behavior in spatially complex aquatic ecosystems.

Aulukluki neqkat: Centering care of salmon and relational research in Indigenous fisheries in the Kuskokwim River, Alaska

This Indigenous-led project aims to better understand historical and contemporary ways in which Alaska Native Peoples steward salmon and the values connected to salmon stewardship. Indigenous Peoples have stewarded Alaska lands and waters for thousands of years yet have been largely excluded from western science and management systems. In this project we utilize a participatory approach that allows for the equitable valuing of ideas and knowledges to document the breadth and depth of Yup’ik and Athabascan knowledge and governance systems in southwestern Alaska. We reshape research methodologies by centering Indigenous frameworks and research methodologies including circle dialogues and multi-generational interviews led by Indigenous scholars and students in their home communities and regions. In this paper, we share the Yup’ik and Athabascan values, knowledge, management, and governance mechanisms that can improve the long-term sustainability and equity of Alaska salmon systems. This research elevates the voices of Alaska Native salmon stewards and experts from the Kuskokwim Bay and the Kuskokwim River. We elaborate on five key themes that emerged from this research including: traditional Indigenous ways of life, Indigenous stewardship, self-determination, food and livelihood sovereignty, and ecosystem changes, and identify a more equitable and sustainable path forward for salmon and people in Alaska.

Herbivores influence biogeochemical processes by altering litter quality and quantity in a subarctic wetland

Global change drivers that modify the quality and quantity of litter inputs to soil affect greenhouse gas fluxes, and thereby constitute a feedback to climate change. Carbon cycling in the Yukon–Kuskokwim (Y–K) River Delta, a subarctic wetland system, is influenced by landscape variations in litter quality and quantity generated by herbivores (migratory birds) that create ‘grazing lawns’ of short stature, nitrogen-rich vegetation. To identify the mechanisms by which these changes in litter inputs affect soil carbon balance, we independently manipulated qualities and quantities of litter representative of levels found in the Y–K Delta in a fully factorial microcosm experiment. We measured CO2 fluxes from these microcosms weekly. To help us identify how litter inputs influenced greenhouse gas fluxes, we sequenced soil fungal and bacterial communities, and measured soil microbial biomass carbon, dissolved carbon, inorganic nitrogen, and enzyme activity. We found that positive correlations between litter input quantity and CO2 flux were dependent upon litter type, due to differences in litter stoichiometry and changes to the structure of decomposer communities, especially the soil fungi. These community shifts were particularly pronounced when litter was added in the form of herbivore feces, and in litter input treatments that induced nitrogen limitation (i.e., senesced litter). The sensitivity of carbon cycling to litter quality and quantity in this system demonstrates that herbivores can strongly impact greenhouse gas fluxes through their influence on plant growth and tissue chemistry.Graphical abstract

Evaluating the viability of the use of T‐bar and radiotelemetry tags on prespawn Arctic Lampreys

AbstractObjectiveArctic Lampreys Lethenteron camtschaticum are harvested by subsistence and commercial fisheries in the Yukon–Kuskokwim River region of Alaska; however, baseline population data are deficient. For mark–recapture and telemetry studies to be effectively implemented to assess Arctic Lamprey abundance, migratory and dispersal patterns, and spawning locations, tags must not impact fish survival, physiology, or behavior.MethodsFor this laboratory evaluation, we examined survival, tag retention, swim endurance at short‐term (1 day posttreatment) and long‐term (43 days [~6 weeks] posttreatment) intervals, and incision healing for T‐bar‐tagged and radio‐tagged prespawn Yukon River Arctic Lampreys (N = 216). Six treatment groups were evaluated: control; sham surgery; external T‐bar anchor tag; and small (0.30 g; 0.1–0.4% tag burden [ratio of tag weight to fish body weight]), medium (0.57 g; 0.2–0.8% tag burden), and large (1.50 g; 0.6–1.9% tag burden) internal dummy radio transmitter tags.ResultAlthough all lampreys survived tagging and surgical procedures through the first 4 weeks of the experiment, a higher tag burden was associated with an increased mortality hazard up to 35 weeks postsurgery. Over the 14‐week experimental period, one T‐bar tag and one small radio tag were shed by lampreys. Although treatment was not a significant predictor of swim endurance, a higher tag burden led to reductions in swim endurance at 1 day posttreatment but not at 43 days posttreatment. Healing did not differ among surgical treatment groups, but persistent inflammation was observed at incision sites and skin erosion was observed at antenna protrusion locations.ConclusionThese results indicate that T‐bar anchor tags and internal radio tags are acceptable for Arctic Lamprey tagging studies if the radio tag burden is ≤1.3% for short‐term (≤14‐week) studies and ≤0.5% for long‐term (≥14‐week) studies.

Sr and Nd Isotopes in Mineral Fractions of Ferromanganese Crusts from the Northernmost Pacific

A study of the isotopic compositions of neodymium and strontium in four mineral fractions of the hydrogenous ferromanganese crusts of the northernmost Pacific has been carried out for the first time. The relationship of the 87Sr/86Sr ratio and εNd value of the residual fraction in heterochronous layers of the ferromanganese crusts have shown that the sources of detrital matter are from rock weathering by the Yukon River, the Kuskokwim River, the Anadyr River and the rivers of Kamchatka. The amount of aluminosilicate impurity does not affect the isotopic compositions of the chemogenic (loosely bound, Mn oxides or manganese, hydrous Fe oxides or ferrous) fractions. The decreased εNd value in the ferrous fraction seems to be related to the presence of rare earth element (REE) phosphate complexes in seawater. The increase in those complexes is a consequence of melt waters entering the ocean during warming periods. Our data indicate that the carbonate REE complexes are not the dominant form of the REEs in the northernmost Pacific, which leads to the fact that the neodymium isotopic compositions of the manganese and ferrous fractions of hydrogenous ferromanganese crusts are different. A decrease in εNd value in the ferrous fraction may be a marker of a local increase in the surface water bioproductivity. Our data also show that the increase of the REE in the ferrous fraction relative to the manganese fraction does not reflect the participation of hydrothermal matter in the formation of mixed hydrogenous–hydrothermal crusts but is a consequence of an increase in the REE phosphate complexes.

Site suitability analysis of hydrokinetic river energy resources at community microgrids on the Kuskokwim River, Alaska

A simple multiparameter tool for quantifying site suitability for riverine hydrokinetic (HK) energy project development is presented and applied to sites in Alaska. Given the high energy costs and diesel fuel dependence of small islanded microgrid communities and adjacent river energy resources, many communities in Alaska are excellent candidates for early adaptation of HK technologies. Seven isolated communities located along the Kuskokwim River in southwest Alaska are evaluated using this method to determine whether riverine HK projects are likely to succeed. While similar models have been developed for wave and tidal energy, to our knowledge, no such tool exists for riverine HK energy. Factors considered in the analysis include the economic viability, energy demand, distance to power distribution lines, HK resource, presence of environmentally sensitive areas, population, and climate change risk or usteq at each community. Modeling of the technical resource adjacent to each community indicates that HK technology could meet or even exceed the energy requirements of the communities during the ice-free open water season (June to October). Although the communities have similar characteristics, the site suitability varies due to variations in the economic, environmental, and technical constraints among the communities. Based on these factors, the most promising community for a riverine HK installation is Aniak, although the highest resource was observed at Chuathbaluk. The approach is easily adaptable to other regions of Alaska or elsewhere with similar hydrologic and geographic constraints.

Overlapping scales: Bias and variability in Alaska Chinook salmon age estimates

Alaska’s Chinook salmon (Oncorhynchus tshawytscha) populations have declined in size at age and age at maturity over the past 30 years, and productivity and adult abundance have decreased during the past decade. Chinook salmon scale age data are used to understand population demography, but methods for scale age estimation may have changed over time and may differ across the state. To begin addressing this, we examined variability and bias associated with age estimates from 10,200 scales, one scale per fish, from five Chinook salmon stocks (Stikine, Copper, Karluk, Nushagak, and Kuskokwim rivers), 1980–2015. This set of scales had an original assigned age, and, from this study, ages estimated by 10 participants (readers) with a range of experience. Variability was assessed using standard deviation (SD) of reader age estimations. We compared SD among stocks, marine ages, time periods (1980–1992, 1993–2005, and 2006–2015), and reader experience. Standard deviation increased by 0.014 for each 10.0 mm difference in fish length from expected length at age. Standard deviation differed among marine ages, with marine age-1 and age-5 scales having 155% and 188% of the variability of marine age-3 scales. Standard deviation did not differ among stocks or time periods. Reader bias was the percentage of scales over or underestimated relative to the median age assignment of 10 readers (the best approximation to known age). Reader bias differed among marine ages with the oldest ages tending to be overestimated and the youngest ages tending to be underestimated. Reader bias decreased with reader experience and was not different among stocks, time periods, or between familiar (those previously examined by a reader) and unfamiliar (new to the reader) stocks. Original ages were underestimated by 3% and overestimated by 9%. Bias in original ages did not differ among stocks, time periods, or marine ages. We provide recommendations, based on our results, for improving the quality of Chinook salmon scale age estimates in the future.

Carbon emissions and radiative forcings from tundra wildfires in the Yukon–Kuskokwim River Delta, Alaska

Abstract. Tundra environments are experiencing elevated levels of wildfire, and the frequency is expected to keep increasing due to rapid climate change in the Arctic. Tundra wildfires can release globally significant amounts of greenhouse gasses that influence the Earth's radiative balance. Here we develop a novel method for estimating carbon loss and the resulting radiative forcings of gaseous and aerosol emissions from the 2015 tundra wildfires in the Yukon–Kuskokwim Delta (YKD), Alaska. We paired burn depth measurements using two vegetative reference points that survived the fire event – Sphagnum fuscum and Dicranum spp. – with measurements of local organic matter and soil carbon properties to estimate total ecosystem organic matter and carbon loss. We used remotely sensed data on fire severity from Landsat 8 to scale our measured losses to the entire fire-affected area, with an estimated total loss of 2.04 Tg of organic matter and 0.91 Tg of carbon and an average loss of 3.76 kg m−2 of organic matter and 1.68 kg m−2 of carbon in the 2015 YKD wildfires. To demonstrate the impact of these fires on the Earth's radiation budget, we developed a simple but comprehensive framework to estimate the radiative forcing from Arctic wildfires. We synthesized existing research on the lifetime and radiative forcings of gaseous and aerosol emissions of CO2, N2O, CH4, O3 and its precursors, and fire aerosols. The model shows a net positive cumulative mean radiative forcing of 3.67 W m−2 using representative concentration pathway (RCP) 4.5 and 3.37 W m−2 using RCP 8.5 at 80 years post-fire, which was dominated by CO2 emissions. Our results highlight the climate impact of tundra wildfires, which positively reinforce climate warming and increased fire frequency through the radiative forcings of their gaseous emissions.

A New Genotyping‐in‐Thousands‐by‐Sequencing Single Nucleotide Polymorphism Panel for Mixed‐Stock Analysis of Chum Salmon from Coastal Western Alaska

AbstractGenetic stock identification is becoming increasingly important in the management of Chum Salmon Oncorhynchus keta from western Alaska due to frequent run failures in recent times. It has been notoriously difficult to distinguish populations of summer‐run Chum Salmon among four major regions in coastal western Alaska: Norton Sound, lower Yukon River, Kuskokwim River, and Nushagak River. Here we developed and evaluated a panel of single nucleotide polymorphism (SNP) markers designed to coamplify using the genotyping‐in‐thousands by sequencing (GT‐seq) method, which would greatly enhance the efficiency of genotyping samples from baseline populations and from mixed‐stock fisheries or incidental catches. We selected 479 SNPs in 355 amplicons from ~30,000 candidate SNPs for the GT‐seq panel. Evaluations using single‐stock and realistic fishery mixture simulations indicated that the panel was able to satisfactorily distinguish Norton Sound from the other regions to the south but was unable to distinguish among lower Yukon, Kuskokwim, and Nushagak rivers with accuracy >90%. The low degree of population structure among Chum Salmon in this region, described in previous studies and confirmed with tens of thousands of SNPs here, means that genetic stock identification will be inadequate to guide management decisions at the spatial scale desired by stakeholders and fishery managers in the region.

Site Suitability Analysis of Hydrokinetic River Energy Resources at Community Microgrids on the Kuskokwim River, Alaska

Site Suitability Analysis of Hydrokinetic River Energy Resources at Community Microgrids on the Kuskokwim River, Alaska

Пространственная ориентация в верхнекускоквимском языке: традиционная система и контактная реинтерпретация

Upper Kuskokwim (Athabaskan, Alaska) uses a developed system of spatial orientation. That system is based on topological axes “upstream vs. downstream” and “uphill vs. downhill” that can be used at a global scale, in application to major elements of the territory: the Kuskokwim river and the Alaska range. After bilingualism and bicultaralism spread among the Upper Kuskokwim people, particular persons came to understand spatial orientation in a somewhat modified way. We can observe that, as a result of language contact, semantics changes and specific reinterpretations emerge in particular idiolects.

Incorporating demographic information into spawner–recruit analyses alters biological reference point estimates for a western Alaska salmon population

Changes over time in age, sex, and length-at-age of returning Pacific salmon have been widely observed, suggesting concurrent declines in per capita reproductive output. Thus, assessment models assuming stationary reproductive output may inaccurately estimate biological reference points that inform harvest policies. We extended age-structured state-space spawner–recruit models to accommodate demographic time trends and fishery selectivity to investigate temporal changes in reference points using Kuskokwim River Chinook salmon (Oncorhynchus tshawytscha). We illustrate that observed demographic changes have likely reduced per capita reproductive output in an additive manner, for example, models including changes in both length-at-age and age composition showed larger declines than models incorporating only one time trend. Translated into biological reference points using a yield-per-recruit algorithm, we found escapement needed for maximum sustained catch has likely increased over time, but the magnitude further depended on size-selective harvest (i.e., larger increases for reference points based on larger mesh gillnets). Compared to traditional salmon assessments, our approach that acknowledges demographic time trends allows more complete use of available data and facilitates evaluating trade-offs among gear-specific harvest policies.

Headwater Catchments Govern Biogeochemistry in America's Largest Free‐Flowing River Network

AbstractRiverine chemistry reflects both watershed conditions and instream processing, both of which vary across river networks, yet little is known about the scales at which watershed attributes regulate biogeochemical constituents. We used spatial stream network (SSN) models to quantify both watershed and instream effects on streamwater constituents in the Kuskokwim River (western Alaska), the largest free‐flowing river in the United States. We assessed chemical constituents spanning from labile nutrients (nitrate [NO3−] and orthophosphate [PO43−]) to biologically and chemically conservative tracers (calcium [Ca2+], strontium [Sr2+], and Sr isotopes [87Sr/86Sr]). We also examined the behavior of dissolved organic carbon (DOC) relative to these constituents to understand whether bulk DOC behaved conservatively in a large boreal river network, where future changes in DOC and nutrient loading are expected under a shifting climate. We derived watershed spatial covariates comprising land cover, geology, and geomorphic characteristics at 14 different spatial extents based on stream order and relative to position in the river network to understand the effect of distant and proximal watershed attributes on streamwater constituents. For all constituents but 87Sr/86Sr, watershed attributes in low‐order headwater catchments yielded the best predictive ability for streamwater constituent concentrations across the entire network. Spatial patterning for conservative tracers and bulk DOC showed strong spatial autocorrelation, whereas PO43− and NO3− exhibited spatial patchiness indicative of instream processing. Our work shows that headwater streams are disproportionately important contributors to network‐wide biogeochemical constituents supporting aquatic food webs and that conservation and management of aquatic systems should include these small and often remote watershed areas.

Density‐dependent effects of eastern Kamchatka pink salmon (Oncorhynchus gorbuscha) and Japanese chum salmon (O. keta) on age‐specific growth of western Alaska chum salmon

AbstractHatcheries release >4.5 billion juvenile Pacific salmon (Oncorhynchus spp.) into the North Pacific Ocean annually, raising concerns about competition with wild salmon populations. We used retrospective scale analysis to investigate how the growth of chum salmon (O. keta) from western Alaska is affected by the abundance of chum salmon from Japanese hatcheries and wild pink salmon (O. gorbuscha) from the Russian Far East. Over nearly five decades, the growth of Kuskokwim River chum salmon was negatively correlated with the abundance of Japanese hatchery chum salmon after accounting for the effects of sex and spring/summer sea‐surface temperature in the Bering Sea. An effect of wild eastern Kamchatka pink salmon abundance on the growth of Kuskokwim River salmon was detectable but modest compared to the intraspecific competitive effect. A decrease in Japanese hatchery chum salmon releases in 2011–2013 was not associated with increased growth of Bering Sea chum salmon. However, the abundance of wild chum salmon from the Russian Far East increased during that time, possibly obscuring reduced competition with hatchery chum salmon. Our results support previous evidence that chum salmon are affected by intraspecific competition, and to a lesser extent interspecific competition, in the North Pacific, underscoring that the effects of salmon hatchery production transcend national boundaries.

On a history of Russian nineteenth century continental explorations in Alaska

In the 1840s, Russian-American Company paid much attention to exploration of the interior of continental Alaska. A ground for such an explorations has been solidly prepared by the Company’s fur extracting activities and by the preceding treks by Vasil’iev, Kolmakov, Glazunov, Malakhov, Lukin and Zagoskin. Russians were by now acquainted in general terms with geography and peoples inhabiting the lower courses of the Kvikhpak (the Yukon) and Kuskokwim rivers. The tribes inhabiting these region, on their part, were informed, at least indirectly, with Russian promyshlenniki’s activities through the process of fur barter trade and by this time did not consider contacts with them as an evil to be avoided at any cost. Zagoskin’s expedition was an outstanding achievement with respect to the study of the environment and population of Alaska’s interior. Arvid Adolf Etholen’s and Voznesenskii’s materials, together with the reports about the remarkable expedition by Zagoskin, attracted close attention of the leadership of the Geographical Society.

Incorporating harvest–population diversity trade-offs into harvest policy analyses of salmon management in large river basins

Accounting for population diversity can be critical to the sustainable management of mixed-stock fisheries because harvest rates that can be sustained by productive populations may come at the cost of overfishing less productive ones. While these harvest–diversity trade-offs are well-recognized, their consequences for harvest policy performance are not often explicitly evaluated in contemporary fisheries management. We use closed-loop simulations to evaluate the ability of alternative harvest policies to meet population diversity and fishery objectives for one of the largest subsistence Chinook salmon (Oncorhynchus tshawytscha) fisheries in the world (Kuskokwim River Basin in western Alaska). We found clear evidence of population diversity that resulted in asymmetric trade-offs among fishery and conservation objectives whereby policies that forgo relatively small amounts of harvest result in relatively large increases in equitable access to Chinook and elimination of risk of weak stock extirpation. The performance of alternative harvest policies, and the magnitude of trade-offs, were sensitive to regime shifts and uncertainty in the drivers of recruitment variation. However, we found that harvest policies that prioritized meeting minimum subsistence needs were unlikely to jeopardize long-term sustainability.

Estimating correlations among demographic parameters in population models.

Estimating correlations among demographic parameters is critical to understanding population dynamics and life‐history evolution, where correlations among parameters can inform our understanding of life‐history trade‐offs, result in effective applied conservation actions, and shed light on evolutionary ecology. The most common approaches rely on the multivariate normal distribution, and its conjugate inverse Wishart prior distribution. However, the inverse Wishart prior for the covariance matrix of multivariate normal distributions has a strong influence on posterior distributions. As an alternative to the inverse Wishart distribution, we individually parameterize the covariance matrix of a multivariate normal distribution to accurately estimate variances (σ 2) of, and process correlations (ρ) between, demographic parameters. We evaluate this approach using simulated capture–mark–recapture data. We then use this method to examine process correlations between adult and juvenile survival of black brent geese marked on the Yukon–Kuskokwim River Delta, Alaska (1988–2014). Our parameterization consistently outperformed the conjugate inverse Wishart prior for simulated data, where the means of posterior distributions estimated using an inverse Wishart prior were substantially different from the values used to simulate the data. Brent adult and juvenile annual apparent survival rates were strongly positively correlated (ρ = 0.563, 95% CRI 0.181–0.823), suggesting that habitat conditions have significant effects on both adult and juvenile survival. We provide robust simulation tools, and our methods can readily be expanded for use in other capture–recapture or capture‐recovery frameworks. Further, our work reveals limits on the utility of these approaches when study duration or sample sizes are small.

Late Quaternary (≥MIS 3 to MIS 1) stratigraphic transitions in a highland Beringian landscape along the Kuskokwim River, Alaska

AbstractStratigraphic records extending to Marine Oxygen Isotope Stage (MIS) 3 (57,000–29,000 cal yr BP) or older in Beringia are extremely rare. Three stratigraphic sections in interior western Alaska show near continuous sedimentological and environmental progressions extending from at least MIS 3, if not older, through MIS 1 (14,000 cal yr BP–present). The Kolmakof, Sue Creek, and VABM (vertical angle bench mark) Kuskokwim sections along the central Kuskokwim River, once a highland landscape at the fringe of central and eastern Beringia, contain aeolian deposition and soil sequences dating beyond 50,00014C yr BP. Thick peaty soil, shallow lacustrine, and tephra deposits represent the MIS 3 interstade (or older). Sand sheet and loess deposits, wedge cast development, and very thin soil development mark the later MIS 3 period and the transition into the MIS 2 stade (29,000–14,000 cal yr BP). Loess accumulation with thicker soil development occurred between ~16,000–13,500 cal yr BP at the MIS 2 and MIS 1 transition. After ~13,500 cal yr BP, loess accumulation waned and peat development increased throughout MIS 1. These stratigraphic sequences represent transitions between a warm and moist period during MIS 3, to a cooler and more arid period during MIS 2, then a return to warmer and moister climates in MIS 1.