skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Contribution of gas concentration and transfer velocity to CO2 flux variability in northern lakes
Abstract The CO2flux () from lakes to the atmosphere is a large component of the global carbon cycle and depends on the air–water CO2concentration gradient (ΔCO2) and the gas transfer velocity (k). Both ΔCO2andkcan vary on multiple timescales and understanding their contributions to is important for explaining variability in fluxes and developing optimal sampling designs. We measured and ΔCO2and derivedkfor one full ice‐free period in 18 lakes using floating chambers and estimated the contributions of ΔCO2andkto variability. Generally,kcontributed more than ΔCO2to short‐term (1–9 d) variability. With increased temporal period, the contribution ofkto variability decreased, and in some lakes resulted in ΔCO2contributing more thankto variability over the full ice‐free period. Increased contribution of ΔCO2to variability over time occurred across all lakes but was most apparent in large‐volume southern‐boreal lakes and in deeper (> 2 m) parts of lakes, whereaskwas linked to variability in shallow waters. Accordingly, knowing the variability of bothkand ΔCO2over time and space is needed for accurate modeling of from these variables. We conclude that priority in assessments should be given to direct measurements of at multiple sites when possible, or otherwise from spatially distributed measurements of ΔCO2combined withk‐models that incorporate spatial variability of lake thermal structure and meteorology.  more » « less
Award ID(s):
1753856
PAR ID:
10540419
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ;
Publisher / Repository:
Wiley
Date Published:
Journal Name:
Limnology and Oceanography
Volume:
69
Issue:
4
ISSN:
0024-3590
Page Range / eLocation ID:
818 to 833
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; (, Geophysical Research Letters)
    Abstract Less than three decades ago only a small fraction of the Arctic Ocean (AO) was ice free and then only for short periods. The ice cover kept sea surfacepCO2at levels lower relative to other ocean basins that have been exposed year round to ever increasing atmospheric levels. In this study, we evaluate sea surfacepCO2measurements collected over a 6‐year period along a fixed cruise track in the Canada Basin. The measurements show that meanpCO2levels are significantly higher during low ice years. ThepCO2increase is likely driven by ocean surface heating and uptake of atmospheric CO2with large interannual variability in the contributions of these processes. These findings suggest that increased ice‐free periods will further increase sea surfacepCO2, reducing the Canada Basin's current role as a net sink of atmospheric CO2. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Limnology and Oceanography Letters)
    Abstract Lakes play a significant role in the global carbon cycle, acting as sources and sinks of carbon dioxide (CO2). In situ measurements of CO2flux (FCO2) from lakes have generally been collected during daylight, despite indications of significant diel variability. This introduces bias when scaling up to whole‐lake annual aquatic carbon budgets. We conducted an international sampling program to ascertain the extent of diel variation in FCO2across lakes. We sampled 21 lakes over 41 campaigns and measured FCO2at 4‐h intervals over a full diel cycle. Rates of FCO2ranged from −3.16 to 4.39 mmol m−2 h−1. Integrated over a day, FCO2ranged from −381.68 to 878.49 mg C m−2d−1(mean = 76.54) across campaigns. We identified three characteristic diel patterns in FCO2related to trophic status and show that for half of the campaigns, daily flux estimates were biased by > 50% if based on a single (daytime) measurement. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Global Biogeochemical Cycles)
    Abstract The Arctic Ocean has turned from a perennial ice‐covered ocean into a seasonally ice‐free ocean in recent decades. Such a shift in the air‐ice‐sea interface has resulted in substantial changes in the Arctic carbon cycle and related biogeochemical processes. To quantitatively evaluate how the oceanic CO2sink responds to rapid sea ice loss and to provide a mechanistic explanation, here we examined the air‐sea CO2flux and the regional CO2sink in the western Arctic Ocean from 1994 to 2019 by two complementary approaches: observation‐based estimation and a data‐driven box model evaluation. ThepCO2observations and model results showed that summer CO2uptake significantly increased by about 1.4 ± 0.6 Tg C decade−1in the Chukchi Sea, primarily due to a longer ice‐free period, a larger open area, and an increased primary production. However, no statistically significant increase in CO2sink was found in the Canada Basin and the Beaufort Sea based on both observations and modeled results. The reduced sea ice coverage in summer in the Canada Basin and the enhanced wind speed in the Beaufort Sea potentially promoted CO2uptake, which was, however, counteracted by a rapidly decreased air‐seapCO2gradient therein. Therefore, the current and future Arctic Ocean CO2uptake trends cannot be sufficiently reflected by the air‐seapCO2gradient alone because of the sea ice variations and other environmental factors. 
    more » « less
  4. ; ; ; (, Environmental Science: Processes & Impacts)
    Accelerated warming in the Arctic has led to concern regarding the amount of carbon emission potential from Arctic water bodies. Yet, aquatic carbon dioxide (CO 2 ) and methane (CH 4 ) flux measurements remain scarce, particularly at high resolution and over long periods of time. Effluxes of methane (CH 4 ) and carbon dioxide (CO 2 ) from Toolik Lake, a deep glacial lake in northern Alaska, were measured for the first time with the direct eddy covariance (EC) flux technique during six ice-free lake periods (2010–2015). CO 2 flux estimates from the lake (daily average efflux of 16.7 ± 5.3 mmol m −2 d −1 ) were in good agreement with earlier estimates from 1975–1989 using different methods. CH 4 effluxes in 2010–2015 (averaging 0.13 ± 0.06 mmol m −2 d −1 ) showed an interannual variation that was 4.1 times greater than median diel variations, but mean fluxes were almost one order of magnitude lower than earlier estimates obtained from single water samples in 1990 and 2011–2012. The overall global warming potential (GWP) of Toolik Lake is thus governed mostly by CO 2 effluxes, contributing 86–93% of the ice-free period GWP of 26–90 g CO 2,eq m −2 . Diel variation in fluxes was also important, with up to a 2-fold (CH 4 ) to 4-fold (CO 2 ) difference between the highest nighttime and lowest daytime effluxes. Within the summer ice-free period, on average, CH 4 fluxes increased 2-fold during the first half of the summer, then remained almost constant, whereas CO 2 effluxes remained almost constant over the entire summer, ending with a linear increase during the last 1–2 weeks of measurements. Due to the cold bottom temperatures of this 26 m deep lake, and the absence of ebullition and episodic flux events, Toolik Lake and other deep glacial lakes are likely not hot spots for greenhouse gas emissions, but they still contribute to the overall GWP of the Arctic. 
    more » « less
  5. ; ; ; ; (, Limnology and Oceanography)
    <italic>Abstract</italic> The attenuation of solar radiation controls many processes and characteristics of aquatic ecosystems and is a sentinel of larger‐scale environmental change. While light attenuation is often characterized with a single broadband diffuse attenuation coefficient of photosynthetically active radiation (KdPAR), attenuation can exhibit substantial variability across the solar spectrum and through time and space. Understanding this variability and its proximate causes may provide information to characterize large‐scale environmental change. We implemented a semi‐analyticalKdmodel in four segments of the Rhode River sub‐estuary of the Chesapeake Bay to examine spectral, spatial, and temporal variability inKdacross the ultraviolet (UV) to PAR wavelengths (290–710 nm) over the period 1986–2014. We used this model to identify wavelengths most sensitive to long‐term change, the seasonal phenology of long‐term change, and the optical constituents driving changes. The model included contributions by phytoplankton,non‐algal particulates,chromophoric dissolved organic matter (CDOM), and water. Over the period of record,Kdincreased (water transparency decreased) in both UV and PAR wavelengths, with the largest increases at the most upstream site, during summer months, and at short UV wavelengths. These increases were due primarily to an increase in non‐algal particulates, and particularly since year 2005, however there was substantial seasonality inKd. The model reveals how different changes in water quality have a differential effect on UV and PAR attenuation, and enables insight into what types of long‐term change in transparency have occurred over the long period of human impacts in the Chesapeake Bay watershed. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email