Investigation of Arctic sea ice and ocean primary production for the period 1992 to 2007 using a 3-D global ice-ocean ecosystem model

In the Arctic Ocean, both phytoplankton and sea ice algae are important contributors to primary production and the arctic food web. An ice algal ecosystem model was added to fully couple with the global physical model POP-CICE (Parallel Ocean Program- Los Alamos Sea Ice Model) and the open-ocean pelagic ecosystem model. The physical model captured the seasonal and interannual variations of northern hemispheric sea ice extent and area measured by satellite remote sensing for the model period of 1992 to 2007. The model results showed a reasonable mean seasonal cycle of ice algal production from March to May and subsequent ocean production from May to September in the Arctic. The ice algal production, although smaller than that of the ocean, is of ecological importance as a food source for higher trophic levels during the long arctic winter before ice melt. The simulated mean open-ocean upper 100m primary production within the Arctic Circle was 413+-88 Tg C ?yr?^(-1) in the years 1998 to 2006, close to the remote sensing derived estimate of 419+-33 Tg C ?yr?^(-1) but with higher interannual variations. The mean sea ice algal production in the Northern Hemisphere from 1998 to 2007 was 21.3 Tg C ?yr?^(-1), which is in the range of multi-observational estimations of 9 to 73 Tg C ?yr?^(-1) based on in situ measurements. Model-data comparisons were conducted with various regional observations and the observed trend of temporal and spatial variation of the primary production. The model results compared well with the following observations and observed trends: 1) an increase of ocean primary production from 2003 to 2007 in the arctic open water areas as derived from remote sensing data; 2) regional annual ice and ocean primary production measured in the Bering and Chukchi seas and Canadian Basin; 3) primary production rate with phytoplankton size composition and Chl-a concentration along an arctic cruise track in the Chukchi Sea and Canadian Basin from August 2 to September 7, 2008; 4) observed decadal changes of ocean primary production from the 1990s to 2007 due to rising temperature and increasing open-ocean area in the western Arctic. The changes are shown as a trend of a northward shift of production, with a decrease in the Bering Sea and an increase in the Arctic shelf.北冰洋中，浮游植物（phytoplankton）与海冰藻类（sea ice algae）均是初级生产与北极食物网的重要贡献者。本研究将冰藻生态系统模型与全球物理模型POP-CICE（并行海洋计划-洛斯阿拉莫斯海冰模型，Parallel Ocean Program- Los Alamos Sea Ice Model）以及开放大洋浮游生态系统模型实现完全耦合。该物理模型在1992至2007年的模拟时段内，准确重现了卫星遥感观测得到的北半球海冰范围与面积的季节及年际变化特征。模型结果合理再现了北极地区3—5月冰藻生产、5—9月后续海洋生产的典型季节循环。尽管冰藻生产量低于海洋浮游植物，但作为北极融冰前漫长冬季中高营养级生物的食物来源，其生态重要性不容忽视。1998至2006年，北极圈内模拟的上层100米开放大洋初级生产平均值为413±88 Tg C·yr⁻¹，与遥感估算的419±33 Tg C·yr⁻¹较为接近，但年际变化幅度更高。1998至2007年北半球海冰藻类平均生产量为21.3 Tg C·yr⁻¹，处于基于原位测量得到的多观测估算区间9~73 Tg C·yr⁻¹之内。本研究通过多类区域观测数据与初级生产时空变化的观测趋势开展了模型-数据对比。模型结果与以下观测及趋势吻合良好：1）2003至2007年北极开阔水域海洋初级生产的遥感观测增长趋势；2）白令海、楚科奇海与加拿大海盆的区域年度冰藻及海洋初级生产实测数据；3）2008年8月2日至9月7日楚科奇海与加拿大海盆北极科考航线上测得的浮游植物粒径组成、叶绿素a（Chl-a）浓度与初级生产速率；4）1990年代至2007年北极西部因气温升高、开阔水域面积增加导致的海洋初级生产年代际变化，该变化表现为生产北移的趋势：白令海初级生产下降，北极陆架区初级生产上升。