Impact of icebergs on net primary productivity in the Southern Ocean

Abstract. Productivity in the Southern Ocean (SO) is iron-limited, and supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine environment. However, recent studies show that icebergs could provide a comparable amount of bioavailable iron to the SO as aeolian dust. In addition, small-scale areal studies suggest increased concentrations of chlorophyll, krill, and seabirds surrounding icebergs. Based on previous research, this study aims to examine whether iceberg occurrence has a significant impact on marine productivity at the scale of the SO, using remote sensing data of iceberg occurrences and ocean net primary productivity (NPP) covering the period 2002–2014. The impacts of both large and small icebergs are examined in four major ecological zones of the SO: the continental shelf zone (CSZ), the seasonal ice zone (SIZ), the permanent open ocean zone (POOZ), and the polar front zone (PFZ). We found that the presence of icebergs is associated with elevated levels of NPP, but the differences vary in different zones. Grid cells with small icebergs on average have higher NPP than other cells in most iron-deficient zones: 21 % higher for the SIZ, 16 % for the POOZ, and 12 % for the PFZ. The difference is relatively small in the CSZ where iron is supplied from meltwater and sediment input from the continent. In addition, NPP of grid cells adjacent to large icebergs on average is 10 % higher than that of control cells in the vicinity. The difference is larger at higher latitudes, where most large icebergs are concentrated. From 1992 to 2014, there is a significant increasing trend for both small and large icebergs. The increase was most rapid in the early 2000s and has leveled off since then. As the climate continues to warm, the Antarctic Ice Sheet is expected to experience increased mass loss as a whole, which could lead to more icebergs in the region. Based on our study, this could result in a higher level of NPP in the SO as a whole, providing a possible negative feedback for global warming in near future.

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Impact of Icebergs on Net Primary Productivity in the Southern Ocean

10.5194/tc-2016-166 ◽

2016 ◽

Author(s):

Shuang-Ye Wu ◽

Shugui Hou

Keyword(s):

Southern Ocean ◽

Primary Productivity ◽

Net Primary Productivity ◽

Positive Impact ◽

Remote Sensing Data ◽

Positive Influence ◽

Small Scale ◽

Linear Regression Models ◽

Comparable Amount ◽

Aeolian Dust

Abstract. Productivity in the Southern Ocean (SO) is iron-limited, and supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine environment. However, recent studies show that icebergs could provide comparable amount of bioavailable iron to the SO as aeolian dust. In addition, small scale areal studies suggest increased concentrations of chlorophyll, krill, and seabirds surrounding icebergs. Based on previous research, this study aims to examine whether iceberg occurrence has a significant impact on marine productivity for the entire SO (south of 40° S), using remote sensing data of monthly iceberg amount and monthly ocean net primary productivity (NPP) covering the period 2002–2014. Using global and geographically weighted multiple linear regression models, and controlling for temperature, our analyses show that iceberg presence has a small, yet statistically significant, positive impact on the SO NPP. NPP in the SO is largely influenced by temperature, which could explain 43 % of the total variance in NPP with the standardized coefficient of 0.68. However, in places with iceberg presence, temperature influence weakens, indicated by lower partial temperature R2 (0.19) and standardized coefficient (0.45). Meanwhile, iceberg probability could independently explain 2 % of the NPP variance with a standardized coefficient of 0.15. Although small, this influence is statistically significant at 0.01 level. The geographically weighted regression model reveals spatial variation of these relationships. The results suggest that as iceberg quantity increases, their positive influence on NPP also increases, as indicated by increasing iceberg partial R2 and standardized coefficient in the models.

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Effects of different sampling scales and selection criteria on modelling net primary productivity of Indonesian tropical forests

Environmental Conservation ◽

10.1017/s0376892913000428 ◽

2013 ◽

Vol 41 (2) ◽

pp. 187-197 ◽

Cited By ~ 2

Author(s):

STEPHAN J. GMUR ◽

DANIEL J. VOGT ◽

KRISTIINA A. VOGT ◽

ASEP S. SUNTANA

Keyword(s):

Cell Size ◽

Primary Productivity ◽

Spatial Data ◽

Selection Criteria ◽

Net Primary Productivity ◽

Climate Change Impacts ◽

Habitat Alterations ◽

Potential Habitat ◽

Production Forests ◽

The Difference

SUMMARYThe availability of spatial data sourced from either field-derived or satellite-based systems has created new opportunities to estimate and/or monitor changes in carbon sequestration rates, climate change impacts or the potential habitat alterations occurring across large landscapes. However, an effort to create models is not standardized, in part, due to different needs and data sources available for the models. For example, data may have different spatial resolutions with varying degrees of complexity in regards to inputs and statistical methods. This study determines effects of 20, 15, 10, five and one km sampling resolutions on detection of changes in net primary productivity (NPP), occupancy selection criteria for areas to be included in the sample and identification of significant variables impacting NPP in Indonesia forests. Production forest designated for selective harvest was used to define the sampling areas. Variances explained by predictive models were similar across cell sizes although relative importance of variables was different. Partial dependence plots were used to search for potential thresholds or tipping points of NPP change as affected by an independent variable such as minimum daytime temperature. Applying different cell occupancy selection rules significantly changed the overall distribution of NPP values. The magnitude of those changes within a cell size varied with changes in cell size. The mean estimated NPP for production forests across Indonesia differed significantly at every sampling resolution and occupancy selection criteria. Lows ranged from 1.107 to 1.121 kg C m−2yr−1for the 1-km cell size for the three occupancy selection criteria with highs ranging from 1.245 to 1.189 kg C m−2yr−1for the 20-km cell size. The difference in NPP values between these two cell sizes for the three occupancy selection criteria extrapolates to a range in annual biomass of 132 × 106to 66 × 106t for the total area of production forests in Indonesia.

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The up-scaling of ecosystem functions in a heterogeneous world

Scientific Reports ◽

10.1038/srep10349 ◽

2015 ◽

Vol 5 (1) ◽

Cited By ~ 22

Author(s):

Andrew M. Lohrer ◽

Simon F. Thrush ◽

Judi E. Hewitt ◽

Casper Kraan

Keyword(s):

Primary Productivity ◽

Ecosystem Functioning ◽

Large Scale ◽

Net Primary Productivity ◽

Marine Ecosystem ◽

Ecosystem Functions ◽

Small Scale ◽

Biodiversity Crisis ◽

Positive Effects ◽

Marine Habitats

Abstract Earth is in the midst of a biodiversity crisis that is impacting the functioning of ecosystems and the delivery of valued goods and services. However, the implications of large scale species losses are often inferred from small scale ecosystem functioning experiments with little knowledge of how the dominant drivers of functioning shift across scales. Here, by integrating observational and manipulative experimental field data, we reveal scale-dependent influences on primary productivity in shallow marine habitats, thus demonstrating the scalability of complex ecological relationships contributing to coastal marine ecosystem functioning. Positive effects of key consumers (burrowing urchins, Echinocardium cordatum) on seafloor net primary productivity (NPP) elucidated by short-term, single-site experiments persisted across multiple sites and years. Additional experimentation illustrated how these effects amplified over time, resulting in greater primary producer biomass (sediment chlorophyll a content) in the longer term, depending on climatic context and habitat factors affecting the strengths of mutually reinforcing feedbacks. The remarkable coherence of results from small and large scales is evidence of real-world ecosystem function scalability and ecological self-organisation. This discovery provides greater insights into the range of responses to broad-scale anthropogenic stressors in naturally heterogeneous environmental settings.

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Evaluating the difference between the normalized difference vegetation index and net primary productivity as the indicators of vegetation vigor assessment at landscape scale

Environmental Monitoring and Assessment ◽

10.1007/s10661-011-2039-1 ◽

2011 ◽

Vol 184 (3) ◽

pp. 1275-1286 ◽

Cited By ~ 32

Author(s):

Chi Xu ◽

Yutong Li ◽

Jian Hu ◽

Xuejiao Yang ◽

Sheng Sheng ◽

...

Keyword(s):

Primary Productivity ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Net Primary Productivity ◽

Landscape Scale ◽

The Difference

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Variations of net primary productivity and phytoplankton community composition in the Indian sector of the Southern Ocean as estimated from ocean color remote sensing data

Biogeosciences ◽

10.5194/bg-9-3875-2012 ◽

2012 ◽

Vol 9 (10) ◽

pp. 3875-3890 ◽

Cited By ~ 13

Author(s):

S. Takao ◽

T. Hirawake ◽

S. W. Wright ◽

K. Suzuki

Keyword(s):

Southern Ocean ◽

Community Composition ◽

Primary Productivity ◽

Phytoplankton Community ◽

Net Primary Productivity ◽

Austral Summer ◽

Remote Sensing Data ◽

The Past ◽

Phytoplankton Community Composition ◽

Indian Sector

Abstract. Phytoplankton population dynamics play an important role in biogeochemical cycles in the Southern Ocean during austral summer. Recent environmental changes such as a rise in sea surface temperature (SST) are likely to impact on net primary productivity (NPP) and phytoplankton community composition. However, their spatiotemporal relationships are still unclear in the Southern Ocean. Here we assessed the relationships between NPP, dominant phytoplankton groups, and SST in the Indian sector of the Southern Ocean over the past decade (1997–2007) using satellite remote sensing data. As a result, we found a statistically significant reduction in NPP in the polar frontal zone over the past decade during austral summer. Moreover, the decrease in NPP positively correlated with the dominance of diatoms (Kendall's rank correlation τ = 0.60) estimated by a phytoplankton community composition model, but not correlated with SST. In the seasonal ice zone, NPP correlated with not only the dominance of diatoms positively (τ = 0.56), but also the dominance of haptophytes (τ = −0.54) and SST (τ = −0.54) negatively. Our results suggested that summer NPP values were strongly affected by the phytoplankton community composition in the Indian sector of the Southern Ocean.

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Variations of net primary productivity and phytoplankton community composition in the Southern Ocean as estimated from ocean-color remote sensing data

Biogeosciences Discussions ◽

10.5194/bgd-9-4361-2012 ◽

2012 ◽

Vol 9 (4) ◽

pp. 4361-4398 ◽

Cited By ~ 1

Author(s):

S. Takao ◽

T. Hirawake ◽

S. W. Wright ◽

K. Suzuki

Keyword(s):

Remote Sensing ◽

Southern Ocean ◽

Community Composition ◽

Primary Productivity ◽

Phytoplankton Community ◽

Net Primary Productivity ◽

Austral Summer ◽

Remote Sensing Data ◽

The Past ◽

Phytoplankton Community Composition

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Global mapping of 10-day differences of temperature and salinity in the intermediate layer observed with Argo floats

Journal of Oceanography ◽

10.1007/s10872-021-00613-6 ◽

2021 ◽

Author(s):

Yoshimi Kawai ◽

Shigeki Hosoda

Keyword(s):

Southern Ocean ◽

The Other ◽

Spatiotemporal Variability ◽

Observation System ◽

Small Scale ◽

Western Boundary ◽

Mariana Islands ◽

Global Mapping ◽

The Difference ◽

Argentine Basin

AbstractThe authors examine small-scale spatiotemporal variability of the layer nearly 2000-m depth, which is the “bottom” of the present Argo observation system, using all of available Argo float data. The 10-day change, ΔT10, is defined as the difference of temperature between two successive observations with an interval of nearly 10 days for each individual float at an isobaric surface. |ΔT10| is large along the western boundary currents at 1000 dbar, and becomes less remarkable with depth. At 1950 dbar, mean |ΔT10| is noticeable in the northeastern Atlantic Ocean (NEAO), the Argentine basin, and the northwestern Indian Ocean. In the Southern Ocean, large |ΔT10| is localized in some areas located over the ridges or leeward of the plateau. Basically, ΔT10 at isobaric surfaces is accounted for by the heave component, but the spiciness component is dominant or comparable to the other in the NEAO and the Argentine basin. ΔT10 decreases with depth monotonically most of the world, suggesting that wind energy input is attenuated with depth. In some areas in the Southern Ocean, however, the vertical profile of |ΔT10| implies enhanced bottom-induced turbulence. |ΔT10| peaks at 1300 dbar in the NEAO, corresponding to the spread of the Mediterranean Outflow Water. |ΔT10| is smaller in the Pacific Ocean compared with the other oceans, but is enhanced along the equator, the Kuroshio and its Extension, the Kuril, Aleutian, Hawaii, and Mariana Islands, and the Emperor Seamount Chain.

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Alternative method for estimating aboveground net primary productivity applied to balsam fir stands in eastern Canada

Canadian Journal of Forest Research ◽

10.1139/x05-052 ◽

2005 ◽

Vol 35 (5) ◽

pp. 1193-1201 ◽

Cited By ~ 8

Author(s):

M B Lavigne ◽

R J Foster ◽

G Goodine ◽

P Y Bernier ◽

C H Ung

Keyword(s):

Primary Productivity ◽

Net Primary Productivity ◽

Carbon Sink ◽

Abies Balsamea ◽

Substantial Effect ◽

Balsam Fir ◽

Aboveground Net Primary Productivity ◽

Eastern Canada ◽

Cross Sectional ◽

The Difference

Aboveground net primary productivity (ANPP) was measured in three balsam fir (Abies balsamea (L.) Mill.) forests on a climatic transect extending from southern New Brunswick ("warm" study area) to central Quebec ("cool" study area). Annual foliar production was estimated with a relationship between cross-sectional area at breast height of the current-year annual xylem ring and the mass of current-year foliage, using data obtained by harvesting trees at the beginning of the study. This relationship differed among study areas. Annual branch production was determined from annual foliar production and the ratio of annual branch production to annual foliar production. The ratio of branch to foliar production was estimated from intensive measurement of a sample of branches collected at the end of the study period; it varied among years but was similar for all study areas. ANPP was 3.36 Mg C·ha1·year1 at the warm study area, 3.73 Mg C·ha1· year1 at the mid-transect study area, and 3.04 Mg C·ha1·year1 at the cool study area. These estimates of ANPP were greater than those estimated using a conventional method of summing up increment and litterfall. On average, the conventional estimate of ANPP was 83% of the estimate using relationships described above. Because net ecosystem productivity is the difference between NPP and heterotrophic respiration, a 17% underestimate of NPP can have a substantial effect on the estimate of carbon-sink activity of a forest.

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