**5. The future of polar benthic blue carbon**

Carbonates already in Antarctic shelf sediment surfaces could become part of the negative feedback if calcite undersaturation is reached on the Antarctic shelves [8]. Ocean acidification is one of the bigger unknowns for the future of polar benthic carbon, in terms of the cost of calcification for organisms, the potential for dissolution whilst alive and after death [28]. Probably the biggest unknown though is how sea temperature will change. There seem to be very different sea temperature trends between the polar regions, across depths and even within seas around the Southern Ocean [29]. The strongest climate-forced trends to date have been in ice extent change. Sea ice losses, glacier retreat and ice shelf collapse are expected to be sustained, although sea ice models are still in their infancy in terms of even recreating the complexity that has already occurred. Salinity changes can be strongly linked to sea ice changes [29] and is likely to remain very important in the Arctic in terms of surface stratification and stabilization impacts. Stratospheric ozone losses have driven seasonal increases in UV and wind strength, driving knock on influences on sea ice (e.g. maintaining open water areas). The impact of all these factors on polar blue carbon to date has been explored to various levels (Sections 3 and 4) such that for some areas summary trends can be erected (**Figure 8**). Because such trends have typically relied on scaling up by area and scaling from few taxa, and rarely accounted for all environmental factors, their main purpose is essentially hypothesis testing markers. Several new independent

research programmes have been recently launched across polar seas to attempt to quantify and model polar carbon capture and storage, including the blue carbon component (**Figure 10**).

**Figure 10.** Apparatus used to estimate surface and sediment carbon and carbonate in polar shelf seas (here shown in the Arctic in 2017). The equipment are shelf underwater camera system (SUCS - above) and multicorer (MUC - below) and

Blue Carbon on Polar and Subpolar Seabeds http://dx.doi.org/10.5772/intechopen.78237 53

their collection products. Note the sponge bisected in one of the core tubes.

Current ideas on the direction of likely trends in polar blue carbon include a wide spectrum of near-future prospects [4, 9, 11, 27, 28]. Reasonable scientific scenarios have been put forward that we can expect drastic reductions in blue carbon storage under current climate projections. These are based on a (largely presumed) inability of polar biodiversity to tolerate lowered pH and increased temperature [9, 13, 27, 28]. This is partly due to the unprecedented level and pace (in recent geological time) of physical change and partly due to the limited options for migration to maintain climate envelope (stay within tolerable conditions). The moderate sea temperature rises expected over the next century could enhance carbon capture and storage [21], although scientific consensus is that more severe temperature rises are likely to reduce polar marine biodiversity performance [27]. However sustained sea ice and ice shelf losses seem likely to increase blue carbon capture and storage rates as to date, but possibly more widespread [16, 17, 26]. Processes by which this could be aided and enhanced, for example creation of artificial polar reefs, have even

**Figure 10.** Apparatus used to estimate surface and sediment carbon and carbonate in polar shelf seas (here shown in the Arctic in 2017). The equipment are shelf underwater camera system (SUCS - above) and multicorer (MUC - below) and their collection products. Note the sponge bisected in one of the core tubes.

**Figure 9.** Cascade of blue carbon through trophic levels and states in polar waters, scaled to mean annual values. Data

Carbonates already in Antarctic shelf sediment surfaces could become part of the negative feedback if calcite undersaturation is reached on the Antarctic shelves [8]. Ocean acidification is one of the bigger unknowns for the future of polar benthic carbon, in terms of the cost of calcification for organisms, the potential for dissolution whilst alive and after death [28]. Probably the biggest unknown though is how sea temperature will change. There seem to be very different sea temperature trends between the polar regions, across depths and even within seas around the Southern Ocean [29]. The strongest climate-forced trends to date have been in ice extent change. Sea ice losses, glacier retreat and ice shelf collapse are expected to be sustained, although sea ice models are still in their infancy in terms of even recreating the complexity that has already occurred. Salinity changes can be strongly linked to sea ice changes [29] and is likely to remain very important in the Arctic in terms of surface stratification and stabilization impacts. Stratospheric ozone losses have driven seasonal increases in UV and wind strength, driving knock on influences on sea ice (e.g. maintaining open water areas). The impact of all these factors on polar blue carbon to date has been explored to various levels (Sections 3 and 4) such that for some areas summary trends can be erected (**Figure 8**). Because such trends have typically relied on scaling up by area and scaling from few taxa, and rarely accounted for all environmental factors, their main purpose is essentially hypothesis testing markers. Several new independent

for the West Antarctic peninsula [16].

52 Carbon Capture, Utilization and Sequestration

**5. The future of polar benthic blue carbon**

research programmes have been recently launched across polar seas to attempt to quantify and model polar carbon capture and storage, including the blue carbon component (**Figure 10**).

Current ideas on the direction of likely trends in polar blue carbon include a wide spectrum of near-future prospects [4, 9, 11, 27, 28]. Reasonable scientific scenarios have been put forward that we can expect drastic reductions in blue carbon storage under current climate projections. These are based on a (largely presumed) inability of polar biodiversity to tolerate lowered pH and increased temperature [9, 13, 27, 28]. This is partly due to the unprecedented level and pace (in recent geological time) of physical change and partly due to the limited options for migration to maintain climate envelope (stay within tolerable conditions). The moderate sea temperature rises expected over the next century could enhance carbon capture and storage [21], although scientific consensus is that more severe temperature rises are likely to reduce polar marine biodiversity performance [27]. However sustained sea ice and ice shelf losses seem likely to increase blue carbon capture and storage rates as to date, but possibly more widespread [16, 17, 26]. Processes by which this could be aided and enhanced, for example creation of artificial polar reefs, have even been financially evaluated but are uneconomical at the current value of industrial carbon capture [30]. Patterns of blue carbon response to climate change are likely to differ strongly between the Arctic and Antarctic, because of their contrasting history and geography, human usage and disparity of current physical change. From current trends it seems most likely that moderate blue carbon increases will occur in Arctic and West Antarctic seas in the near future to be eventually replaced by more severe decreases when critically low pH and high temperatures begin to be reached. Predicting physical trends and blue carbon biological responses in East Antarctic seas is more difficult because of current variability and lack of sustained patterns. It seems intuitively likely that East Antarctic blue carbon patterns may ultimately follow those of other polar locations but with a considerable lag phase. Given the rarity of natural negative feedbacks on climate change and the importance of blue carbon as a current negative feedback, quantification and understanding of polar blue carbon change should be high as a scientific priority.

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