Amplified Arctic Surface Warming and Sea Ice Loss Due to Phytoplankton and Colored Dissolved Material

Abstract

Optically active water constituents attenuate solar radiation and hence affect the vertical distribution of energy in the upper ocean. To understand their implications, we operate an ocean biogeochemical model coupled to a general circulation model with sea ice. Incorporating the effect of phytoplankton and colored dissolved organic matter (CDOM) on light attenuation in the model increases the sea surface temperature in summer and decreases sea ice concentration in the Arctic Ocean. Locally, the sea ice season is reduced by up to one month. CDOM drives a significant part of these changes, suggesting that an increase of this material will amplify the observed Arctic surface warming through its direct thermal effect. Indirectly, changing advective processes in the Nordic Seas may further intensify this effect. Our results emphasize the phytoplankton and CDOM feedbacks on the Arctic ocean and sea ice system and underline the need to consider these effects in future modeling studies to enhance their plausibility. Plain Language Summary The amount of microalgae and colored dissolved organic material in the ocean determines how much light is absorbed in the surface waters and how much can reach greater depths. The vertical distribution of energy affects the upper ocean temperature and general circulation. Here, we use a numerical ocean model with biogeochemistry and sea ice, in which the individual effects of microalgae and colored dissolved organic matter can be turned on and off separately. When both effects are turned on, the summertime surface temperatures in the Arctic are larger and consequently more sea ice melts, so that the sea ice season is shorter by up to one month. We find that, to a large extent, the colored dissolved material is responsible for these changes. An increase of this material due to climate change will amplify the observed Arctic surface warming. For better projections of climate change, new models should account for the effect of these light-absorbing water constituents. In numerical ocean general circulation models, the penetration of solar radiation needs to be parameterized. The choice of parameterization may affect the circulation significantly, as well as the upper ocean water masses (Cahill et al., 2008) and their transformation rates (Groeskamp & Iudicone, 2018). Compared RESEARCH LETTER

Stronger Arctic amplification from ozone-depleting substances than from carbon dioxide

“…Much attention has been devoted to exploring the mechanisms behind AA. Many studies have emphasized the role of local feedback processes e.g., Goosse et al (2018), Stuecker et al (2018), Beer et al (2020), Feldl et al (2020), Chung et al (2021), of heat and moisture transport from lower latitudes e.g., Hwang et al (2011), Graversen and Burtu (2016), Gong et al (2017), Yang and Magnusdottir (2017), Yoshimori et al (2017), Graversen and Langen (2019), or even of biological processes e.g., Swann et al (2010), Park et al (2015Park et al ( , 2020, Pefanis et al (2020). However, much uncertainty remains as to the relative contributions from the many proposed mechanisms (Previdi et al 2021).…”

Impact of Vertical Mixing on Summertime Net Community Production in Canadian Arctic and Subarctic Waters: Insights From In Situ Measurements and Numerical Simulations

“…Rivers surrounding HB were not sampled at the time of our cruises, but supporting observations from that region in June 2018 suggest similarly‐high DOC concentrations (black markers in Figure 8b). These measurements are also reflected in satellite‐based observations of elevated colored dissolved organic matter (taken by‐proxy as the absorption at 443 nm; Pefanis et al., 2020), which were high in QMG and HB (Figure 8b). We thus propose that the low cor‐NCP, and the shift toward net heterotrophy in the QMG and HB, may reflect a signature of community respiration driven by allochthonous organic material.…”

“…The Chl a data are from an Arctic‐specific satellite product (Section 2.2), and salinity data (average in the upper 10 m) are from the World Ocean Database (https://www.nodc.noaa.gov/OC5/WOD/pr_wod.html). Absorption data were taken as a proxy for colored dissolved organic matter (Pefanis et al., 2020), and were obtained from the NASA L3 MODIS‐Aqua Ocean Color product (https://oceancolor.gsfc.nasa.gov/l3/). The relative concentrations of N + N and dissolved organic carbon measured in rivers sampled near the cruise tracks are shown as red and black markers in panels (a and b), respectively.…”

Optical remote sensing (Sentinel-3 OLCI) used to monitor dissolved organic carbon in the Lena River, Russia

“…Warming and consequently degrading permafrost is expected to mobilize large amounts of organic carbon that was previously stored in frozen soil and sediment, which is then susceptible to decomposition, sedimentation and/or transport via rivers into the Arctic Ocean (Guo et al, 2007;Frey & McClelland, 2009;Wild et al, 2019). Major changes in riverine land-to-sea fluxes of organic matter, especially dissolved organic matter and its colored dissolved fraction (colored dissolved organic matter, CDOM), can affect the Arctic Ocean in multiple ways, such as decreasing transparency of the water, increasing radiative heating of the surface waters (Soppa et al, 2019;Pefanis et al, 2020), and acidification of the shelf waters (Semiletov et al, 2016). These processes will change the marine ecosystem and primary production in the Arctic shelf seas (Terhaar et al, 2021).…”