Editing IPCC:AR6/WGI/Chapter-2 (section)

===== 2.3.4.2.2 Marine primary production =====

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SROCC expressed ''low confidence'' in satellite-based estimates of trends in marine primary production, citing insufficient length of the time series and lack of corroborating in situ measurements and independent validation time series. The report also cites significant mismatches in absolute values and decadal trends in primary production when different satellite-based products are compared.

Recent model-based results with assimilation of satellite data ( [[#Gregg--2019|Gregg and Rousseaux, 2019]] ), show global annual mean marine primary production of around 38 (±1.13) PgC yr <sup>–1</sup> over 1998–2015. This new result lies towards the low end of values reported in earlier, satellite-based, studies (range 36.5–67 PgC yr <sup>–1</sup> , reported in [[#Sathyendranath--2020|Sathyendranath et al. (2020)]] ). Reconciling the results of [[#Gregg--2019|Gregg and Rousseaux (2019)]] with earlier satellite-based studies leads to a mean of 47 (±7.8) PgC yr <sup>–1</sup> . There is a strong correlation between interannual regional variability in marine primary production and climate variability ( [[#Racault--2017b|Racault et al., 2017b]] ; [[#Gregg--2019|Gregg and Rousseaux, 2019]] ). The increase in primary production in the Arctic has been associated with retreating sea ice and with increases in nutrient supply and chlorophyll concentration ( [[#Lewis--2020|Lewis et al., 2020]] ). [[#Gregg--2019|Gregg and Rousseaux (2019)]] reported a decreasing trend in marine primary production, of –0.8 PgC (–2.1%) per decade globally. There is ''low confidence'' in this trend because of the small number of studies and the short length of the time series (&lt;20 years).

In conclusion, there is ''low confidence'' because of the small number of recent studies and the insufficient length of the time series analysed that marine primary production is 47 (± 7.8) PgC yr <sup>–1</sup> . A small decrease in productivity is evident globally for the period 1998–2015, but regional changes are larger and of opposing signs ( ''low confidence'' ).

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