Peter A Raymond

Yale University | YU · School of Forestry and Environmental Studies

Hydrological precipitation and snow melt events trigger large "Pulse" releases of terrestrial DOM into drainage networks due to an increase in concentration with discharge. Thus low frequency large events, which are predicted to increase with climate change, are responsible for a significant percentage of annual terrestrial DOM input to drainage ne...

Climate-sensitive northern cryosphere inland waters emit greenhouse gases (GHGs) into the atmosphere, yet their total emissions remain poorly constrained. We present a data-driven synthesis of GHG emissions from northern cryosphere inland waters considering water body types, cryosphere zones, and seasonality. We find that annual GHG emissions are d...

Rivers are a key component of the global carbon cycle. They receive vast quantities of terrestrial carbon, of which a large fraction is ultimately exported to the coastal ocean. Our review of previously published assessments reveals that substantial uncertainties remain with regard to the spatial distribution and speciation of the carbon export. Ac...

Quantifying the relative influence of factors and processes controlling riverine ecosystem function is essential to predicting future conditions under global change. Dissolved organic matter (DOM) is a fundamental component of riverine ecosystems that fuels microbial food webs, influences nutrient and light availability, and represents a significan...

There is growing evidence that the composition of river microbial communities gradually transitions from terrestrial taxa in headwaters to unique planktonic and biofilm taxa downstream. Yet, little is known about fundamental controls on this community transition across scales in river networks. We hypothesized that community composition is controll...

Ephemeral streams flow only in direct response to precipitation and are ubiquitous landscape features. However, little is known about their influence on downstream rivers. Here, we modeled ephemeral stream water contributions to the contiguous United States network of more than 20 million rivers, lakes, and reservoirs, finding that ephemeral stream...

An accurate quantification of global methane sources and sinks is imperative for assessing realistic pathways to mitigate climate change. A key challenge of quantifying the Global Methane Budget (Saunois et al., 2020, https://doi.org/10.5194/essd‐12‐1561‐2020) is the lack of consistency in uncertainties between sectors. Here we provide a new perspe...

Nitrous oxide (N2O) is a long-lived potent greenhouse gas and stratospheric ozone-depleting substance that has been accumulating in the atmosphere since the preindustrial period. The mole fraction of atmospheric N2O has increased by nearly 25 % from 270 ppb (parts per billion) in 1750 to 336 ppb in 2022, with the fastest annual growth rate since 19...

Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Emissions and atmospheric concentrations of CH4 continue to increase, maintaining CH4 as the second most important human-influenced greenhouse gas in terms of climate forcing after carbon dioxide (CO2). The relativ...

Cities are at the heart of global anthropogenic greenhouse gas (GHG) emissions, with rivers embedded in urban landscapes as a potentially large yet uncharacterized GHG source. Urban rivers emit GHGs due to excess carbon and nitrogen inputs from urban environments and their watersheds. Here relying on a compiled urban river GHG dataset and robust mo...

Quantifying the relative influence of factors and processes controlling riverine ecosystem function is essential to predicting future conditions under global change. Dissolved organic matter (DOM) is a fundamental component of riverine ecosystems that fuels microbial food webs, influences nutrient and light availability, and represents a significan...

The Anthropocene is defined by marked acceleration in human-induced perturbations to the Earth system. Anthropogenic emissions of CO2 and other greenhouse gases to the atmosphere and attendant changes to the global carbon cycle are among the most profound and pervasive of these perturbations. Determining the magnitude, nature and pace of these carb...

Radiocarbon (¹⁴C) is a critical tool for understanding the global carbon cycle. During the Anthropocene, two new processes influenced ¹⁴C in atmospheric, land and ocean carbon reservoirs. First, ¹⁴C-free carbon derived from fossil fuel burning has diluted ¹⁴C, at rates that have accelerated with time. Second, ‘bomb’ ¹⁴C produced by atmospheric nucl...

Nitrous oxide (N2O) is a long-lived potent greenhouse gas and stratospheric ozone-depleting substance, which has been accumulating in the atmosphere since the pre-industrial period. The mole fraction of atmospheric N2O has increased by nearly 25 % from 270 parts per billion (ppb) in 1750 to 336 ppb in 2022, with the fastest annual growth rate since...

Rivers integrate processes occurring throughout their watersheds and are therefore sentinels of change across broad spatial scales. River chemistry also regulates ecosystem function across Earth’s land–ocean continuum, exerting control from the micro- (for example, local food web) to the macro- (for example, global carbon cycle) scale. In the rapid...

Methane (CH4) is a potent greenhouse gas and its concentrations have tripled in the atmosphere since the industrial revolution. There is evidence that global warming has increased CH4 emissions from freshwater ecosystems1,2, providing positive feedback to the global climate. Yet for rivers and streams, the controls and the magnitude of CH4 emission...

Riverine dissolved iron (Fe) affects water color, nutrients, and marine carbon cycling. Fe size and coupling with dissolved organic matter (DOM), in part, modulates the biogeochemical roles of riverine Fe. We used size fractionation to operationally define dissolved Fe (< 0.22 μ m) into soluble (< 0.02 μ m) and colloidal (0.02–0.22 μ m) fractions i...

Arctic rivers provide an integrated signature of the changing landscape and transmit signals of change to the ocean. Here, we use a decade of particulate organic matter (POM) compositional data to deconvolute multiple allochthonous and autochthonous pan-Arctic and watershed-specific sources. Constraints from carbon-to-nitrogen ratios (C:N), δ13C, a...

River networks transport dissolved organic carbon (DOC) from terrestrial uplands to the coastal ocean. The extent to which a reach or lake within a river network uptakes DOC depends on the stream order, the seasonal conditions, and the flow. At the watershed scale, it remains unclear whether DOC uptake is dominated by biological processes such as r...

Large rivers integrate processes occurring throughout their watersheds, and are therefore sentinels of change across broad spatial scales. Riverine chemistry also regulates ecosystem function across Earth’s land-ocean continuum, exerting control from the micro- (e.g., food web) to the macro- (e.g., carbon cycle) scale. In the rapidly warming Arctic...

Two decades of research has shown that the global river network emits significant amounts of greenhouse gas. Despite much progress, there is still large uncertainty in the temporal dynamics of gas exchange and thus carbon emissions to the atmosphere. Much of this uncertainty stems from a lack of existing tools for studying the spatiotemporal dynami...

Dissolved organic matter (DOM) impacts the structure and function of aquatic ecosystems. DOM absorbs light in the UV and visible (UV–Vis) wavelengths, thus impacting light attenuation. Because absorption by DOM depends on its composition, UV–Vis absorbance is used to constrain DOM composition, source, and amount. Ferric iron, Fe(III), also absorbs...

The relative capacity for watersheds to eliminate or export reactive constituents has important implications on aquatic ecosystem ecology and biogeochemistry. Removal efficiency depends on factors that affect either the reactivity or advection of a constituent within river networks. Here, we characterized Damköhler number (Da) for dissolved organic...

Significance Stream/river carbon dioxide (CO 2 ) emission has significant spatial and seasonal variations critical for understanding its macroecosystem controls and plumbing of the terrestrial carbon budget. We relied on direct fluvial CO 2 partial pressure measurements and seasonally varying gas transfer velocity and river network surface area est...

Nitrous oxide (N2O) evasion from streams and rivers is a significant, yet highly uncertain, flux in nitrogen cycle models. Most global estimates of lotic N2O emission assume that evasion rates are proportional to inorganic nitrogen inputs to a stream or river. However, many field studies do not detect relationships between lotic N2O evasion and dis...

Significance Mercury is a globally ubiquitous pollutant that is harmful to humans and animals. Most mercury entering the environment is released from anthropogenic sources and then stored for some period in soils and water bodies before potentially being remobilized, which greatly facilitates its global distribution. Although the ocean is recognize...

Plain Language Summary Nitrous oxide (N2O) is the third most important greenhouse gase (GHG) after CO2 and CH4 causing global warming. Among world regions, North America (defined herein as U.S., Canada, and Mexico) is the second largest source of N2O emissions globally, and previous source estimates for this region vary widely. This study aims to p...

This study focuses on characterizing the contributions of key terrestrial pathways that deliver dissolved organic carbon (DOC) to streams during hydrological events and on elucidating factors governing variation in water and DOC fluxes from these pathways. We made high‐frequency measurements of discharge, specific conductance (SC), and fluorescent...

Mercury is a potent neurotoxic substance and accounts for 250,000 intellectual disabilities annually. Worldwide, coastal fisheries contribute the majority of human exposure to mercury through fish consumption. Recent global mercury cycling and risk models attribute all the mercury loading to the ocean to atmospheric deposition. Nevertheless, new re...

The ongoing development of the Global Carbon Project (GCP) global methane (CH4) budget shows a continuation of increasing CH4 emissions and CH4 accumulation in the atmosphere over 2000‐2017. Here we decompose the global budget into 19 regions (18 land and one oceanic) and five key source sectors to spatially attribute the observed global trends. A...

Streams and rivers are significant sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the magnitudes of these fluxes are uncertain, in part, because dissolved greenhouse gases (GHGs) can exhibit high spatiotemporal variability. Concentration‐discharge (C‐Q) relationships are commonly used to describe temporal variability...

Climate change is melting glaciers and altering watershed biogeochemistry across the globe, particularly in regions dominated by mountain glaciers, such as southeast Alaska. Glacier dominated watersheds exhibit distinct dissolved organic matter (DOM) characteristics compared to forested and vegetated watersheds. However, there is a paucity of infor...

Aquatic primary productivity produces oxygen (O2) and consumes carbon dioxide (CO2) in a ratio of ~1.2. However, in aquatic ecosystems, dissolved CO2 concentrations can be low, potentially limiting primary productivity. Here, results show that a large drainage basin maintains its highest levels of gross primary productivity (GPP) when dissolved CO2...

Climate change is dramatically altering Arctic ecosystems, leading to shifts in the sources, composition, and eventual fate of riverine dissolved organic matter (DOM) in the Arctic Ocean. Here we examine a 6‐year DOM compositional record from the six major Arctic rivers using Fourier‐transform ion cyclotron resonance mass spectrometry paired with d...

Dissolved organic carbon (DOC) impacts water quality, the carbon cycle, and the ecology of aquatic systems. Understanding what controls DOC is therefore critical for improving large-scale models and best management practices for aquatic ecosystems. The two main processes of DOC transformation and removal, photochemical and microbial DOC degradation...

Atmospheric methane is a potent greenhouse gas that plays a major role in controlling the Earth’s climate. The causes of the renewed increase of methane concentration since 2007 are uncertain given the multiple sources and complex biogeochemistry. Here, we present a metadata analysis of methane fluxes from all major natural, impacted and human-made...

Most terrestrial allochthonous organic matter enters river networks through headwater streams during high flow events. In headwaters, allochthonous inputs are substantial and variable, but become less important in streams and rivers with larger watersheds. As allochthonous dissolved organic matter (DOM) moves downstream, the proportion of less arom...

Climate change is melting glaciers and altering watershed biogeochemistry across the globe, particularly in regions dominated by mountain glaciers, such as southeast Alaska. Glacier dominated watersheds exhibit distinct dissolved organic matter (DOM) characteristics compared to forested and vegetated watersheds. However, there is a paucity of infor...

Nitrous oxide, N2O, is the leading cause of stratospheric ozone depletion and one of the most potent greenhouse gases (GHG). Its concentration in the atmosphere has been rapidly increasing since the green revolution in the 1950s and 1960s. Riverine systems have been suggested to be an important source of N2O, although their quantitative contributio...

Plain Language Summary The thaw of continuously frozen grounds in the Arctic induced by regional warming accelerates the release of carbon to the atmosphere and river systems. Of particular concern is the fate of dissolved organic carbon (DOC) due to its potential for rapid oxidation to carbon dioxide. In order to understand the ramifications of a...

Groundwater discharge to river networks makes up a major source of riverine CO2 emission, available evidence however comes mainly from headwater streams which are directly connected to terrestrial ecosystems and spatially limited in terms of system size. Here relying on coupled water and CO2 mass balances, we quantified the groundwater-mediated CO2...

Nitrous oxide (N2O), like carbon dioxide, is a long-lived greenhouse gas that accumulates in the atmosphere. Over the past 150 years, increasing atmospheric N2O concentrations have contributed to stratospheric ozone depletion¹ and climate change², with the current rate of increase estimated at 2 per cent per decade. Existing national inventories do...

The magnitude of future emissions of greenhouse gases from the northern permafrost region depends crucially on the mineralization of soil organic carbon (SOC) that has accumulated over millennia in these perennially frozen soils. Many recent studies have used radiocarbon (¹⁴C) to quantify the release of this “old” SOC as CO2 or CH4 to the atmospher...

Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 continue to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). The relative impor...

Resolving regional carbon budgets is critical for informing land-based mitigation policy. For nine regions covering nearly the whole globe, we collected inventory estimates of carbon-stock changes complemented by satellite estimates of biomass changes where inventory data are missing. The net land–atmospheric carbon exchange (NEE) was calculated by...

Inland waters are large sources of methane to the atmosphere. However, considerable uncertainty exists in estimating the emissions of this potent greenhouse gas from global streams and rivers due, in part, to a lack of direct measurements in the high-altitude cryosphere and poor accounting for ebullition. Here we present methane concentrations and...

Carbonaceous matter in the atmosphere has an important influence on climate change. Currently, the deposition of carbonaceous matter is one of the largest uncertainties in the climate system. This phenomenon is common in remote regions, such as the Himalayas and Tibetan Plateau. In this study, for the first time, we reported in situ measurements of...

Abstract Carbonaceous matter in the atmosphere has an important influence on climate change. Currently, the deposition of carbonaceous matter is one of the largest uncertainties in the climate system. This phenomenon is common in remote regions, such as the Himalayas and Tibetan Plateau. In this study, for the first time, we reported in situ measu...

The Tibetan Plateau is a critical ecosystem that sensitively responds to ongoing glacier shrinkage and permafrost thaw. Dissolved organic matter (DOM) in Tibetan Alpine rivers plays pivotal roles in the biogeochemical cycling of elements and nutrients at regional and even global scales, impacting water quality, downstream environments, and climate....

Climate warming is expected to mobilize northern permafrost and peat organic carbon (PP-C), yet magnitudes and system specifics of even current releases are poorly constrained. While part of the PP-C will degrade at point of thaw to CO2 and CH4 to directly amplify global warming, another part will enter the fluvial network, potentially providing a...

Hydrological events, driven by rainfall, control the amount and composition of dissolved organic matter (DOM) mobilized through river networks. In forested watersheds, the concentration, composition, and reactivity of DOM exported changes as baseflow transitions to storm flow, with major implications to downstream biogeochemistry. Hysteresis descri...

Streams and rivers emit petagrams of CO2, yet there is little known about how discharge variability impacts stream CO2 at broad scales. This article analyzed changes of pCO2 and CO2 efflux with discharge in 813 conterminous US streams and rivers. Half of the streams and rivers (49%) showed positive pCO2–discharge responses, while significantly more...

High‐latitude lakes are sensitive indicators of climate and important ecological components of Northern landscapes. The response of Arctic lakes to accelerated 20th century warming has largely been inferred from paleolimnological and shorter‐term observational studies (< 20 yr). Here, we present a long‐term observational dataset outlining a suite o...

Lakes play an important role in the global carbon cycle, and littoral zones of lakes are potential hotspots of greenhouse gas production. In this study, we measured the partial pressures of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in the littoral zones of 17 lakes on the Tibetan Plateau. The littoral zones of lakes on the Tibeta...

The dissolved organic carbon in precipitation (water-soluble organic carbon, WSOC) can provide a carbon subsidy to receiving ecosystems. The concentrations, isotopic signatures (δ¹³C/Δ¹⁴C), and molecular signatures (transform ion cyclotron mass spectrometry) of WSOC being delivered to Nam Co—a remote site on the inland Tibetan Plateau (TP)—were com...

Bicarbonate (HCO3−), the predominant form of dissolved inorganic carbon in natural waters, originates mostly from watershed mineral weathering. On time scales of decades to centuries, riverine fluxes of HCO3− to the oceans and subsequent reactions affect atmospheric CO2, global climate and ocean pH. This review summarizes controls on the production...

The flux of terrestrial C to rivers has increased relative to pre-industrial levels, a fraction of which is aged dissolved organic C (DOC). In rivers, C is stored in sediments, exported to the ocean, or (bio)chemically processed and released as CO2. Disturbance changes land cover and hydrology, shifting potential sources and processing of DOC. To i...