Response of ocean ecosystems to climate warming

Abstract

[1] We examine six different coupled climate model simulations to determine the ocean biological response to climate warming between the beginning of the industrial revolution and 2050. We use vertical velocity, maximum winter mixed layer depth, and sea ice cover to define six biomes. Climate warming leads to a contraction of the highly productive marginal sea ice biome by 42% in the Northern Hemisphere and 17% in the Southern Hemisphere, and leads to an expansion of the low productivity permanently stratified subtropical gyre biome by 4.0% in the Northern Hemisphere and 9.4% in the Southern Hemisphere. In between these, the subpolar gyre biome expands by 16% in the Northern Hemisphere and 7% in the Southern Hemisphere, and the seasonally stratified subtropical gyre contracts by 11% in both hemispheres. The low-latitude (mostly coastal) upwelling biome area changes only modestly. Vertical stratification increases, which would be expected to decrease nutrient supply everywhere, but increase the growing season length in high latitudes. We use satellite ocean color and climatological observations to develop an empirical model for predicting chlorophyll from the physical properties of the global warming simulations. Four features stand out in the response to global warming: (1) a drop in chlorophyll in the North Pacific due primarily to retreat of the marginal sea ice biome, (2) a tendency toward an increase in chlorophyll in the North Atlantic due to a complex combination of factors, (3) an increase in chlorophyll in the Southern Ocean due primarily to the retreat of and changes at the northern boundary of the marginal sea ice zone, and (4) a tendency toward a decrease in chlorophyll adjacent to the Antarctic continent due primarily to freshening within the marginal sea ice zone. We use three different primary production algorithms to estimate the response of primary production to climate warming based on our estimated chlorophyll concentrations. The three algorithms give a global increase in primary production of 0.7% at the low end to 8.1% at the high end, with very large regional differences. The main cause of both the response to warming and the variation between algorithms is the temperature sensitivity of the primary production algorithms. We also show results for the period between the industrial revolution and 2050 and 2090.

Pacific walruses, indigenous hunters, and climate change: Bridging scientific and indigenous knowledge

“…Assumptions about Beringian resiliency have recently been brought into question by abundant evidence that climate warming is occurring and is affecting the entire Beringian ecosystem, including walruses (Grebmeier et al, 2006;Sarmiento et al, 2004;Smetacek and Nicol, 2005;Ray et al, 2006). A major regime shift and a cascade of consequent effects appear inevitable.…”

“…We do know that sea ice is a key factor in walrus distribution and population dynamics, due to the walrus' dependency on it as a habitat for reproduction and feeding (Fay, 1982;Fay et al, 1984;Ray and Hufford, 1989). Sea ice is also the feature of polar ecosystems most subject to rapid climate change (Sarmiento et al, 2004;Smetacek and Nicol, 2005). This creates a critical need to Hnk processes and information about sea ice, walruses, and indigenous people who depend on walrus for their economic and social wellbeing.…”

Winners and losers: Ecological and biogeochemical changes in a warming ocean

“…[4] Published numerical projections of future oceans suggest very different changes in global integrated primary production in future scenarios [Sarmiento et al, 2004;Schmittner et al, 2008;Steinacher et al, 2010;Marinov et al, 2010;Taucher and Oschlies, 2011;Bopp et al, 2005;Bopp et al, 2013], even disagreeing on the sign of the net change. Locally, there are only select regions of general agreement between models, with other regions of disparate signs of changes [Bopp et al, 2013].…”

Phytoplankton community structure in relation to vertical stratification along a north‐south gradient in the Northeast Atlantic Ocean

“…As global warming continues, the surface waters of the ocean are envisaged to rise by 2-68C over the next 100 yrs (Meehl et al 2007;Collins et al 2013). Ocean-climate models predict that surface warming, in combination with changes in freshwater input at high latitudes (due to rises in precipitation, land run off and sea ice melt) will lead to increases in vertical stratification (Sarmiento et al 1998;Sarmiento 2004). Vertical stratification affects the production of the world's oceans as it determines the general availability of light and nutrients to phytoplankton in the ocean (Behrenfeld et al 2006;Huisman et al 2006;Hoegh-Guldberg and Bruno 2010).…”