Mesozooplankton standing stock during the North Atlantic spring bloom study in 1989 and its potential grazing pressure on phytoplankton: a comparison between low, medium and high latitudes

Vegetation in the northern high latitudes shows a characteristic pattern of persistent changes as documented by multi-decadal satellite observations. The prevailing explanation that these mainly increasing trends (greening) are a consequence of external CO2 forcing, i.e., due to the ubiquitous effect of CO2-induced fertilization and/or warming of temperature-limited ecosystems, however does not explain why some areas also show decreasing trends of vegetation cover (browning). We propose here to consider the dominant mode of multi-decadal internal climate variability in the north Atlantic region, the Atlantic Multidecadal Variability (AMV), as the missing link in the explanation of greening and browning trend patterns in the northern high latitudes. Such a link would also imply potential for decadal predictions of ecosystem changes in the northern high latitudes.An analysis of observational and reanalysis data sets for the period 1979-2019 shows that locations characterized by greening trends largely coincide with warming summer temperature and increasing precipitation. Wherever either cooling or decreasing precipitation occurs, browning trends are observed over this period. These precipitation and temperature patterns are significantly correlated with a North Atlantic sea surface temperature index that represents the AMV signal, indicating its role in modulating greening/browning trend patterns in the northern high latitudes.Using two large ensembles of coupled Earth system model simulations (100 members of MPI-ESM-LR Grand Ensemble and 32 members of the IPSL-CM6A-LR Large Ensemble), we separate the greening/browning pattern caused by external CO2 forcing from that caused by internal climate variability associated with the AMV. These sets of model simulations enable a clean separation of the externally forced signal from internal variability. While the greening and browning patterns in the simulations do not agree with observations in terms of magnitude and location, we find consistent internally generated greening/browning patterns in both models caused by changes in temperature and precipitation linked to the AMV signal. These greening/browning trend patterns are of the same magnitude as those caused by the external forcing alone. Our work therefore shows that internally-generated changes of vegetation in the northern lands, driven by AMV, are potentially as large as those caused by external CO2 forcing. We thus argue that the observed pattern of greening/browning in the northern high latitudes could originate from the combined effect of rising CO2 as well as the AMV.

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Optimizing models of the North Atlantic spring bloom using physical, chemical and bio-optical observations from a Lagrangian float

Biogeosciences Discussions ◽

10.5194/bgd-7-8477-2010 ◽

2010 ◽

Vol 7 (6) ◽

pp. 8477-8520 ◽

Cited By ~ 1

Author(s):

W. Bagniewski ◽

K. Fennel ◽

M. J. Perry ◽

E. A. D'Asaro

Keyword(s):

North Atlantic ◽

Spring Bloom ◽

Deep Ocean ◽

Complex Model ◽

Optical Observations ◽

Model Parameters ◽

Carbon Export ◽

The North ◽

Chemical Measurements ◽

The North Atlantic

Abstract. The North Atlantic spring bloom is one of the main events that lead to carbon export to the deep ocean and drive oceanic uptake of CO2 from the atmosphere. Here we use a suite of physical, bio-optical and chemical measurements made during the 2008 spring bloom to optimize and compare three different models of biological carbon export. The observations are from a Lagrangian float that operated south of Iceland from early April to late June, and were calibrated with ship-based measurements. The simplest model is representative of typical NPZD models used for the North Atlantic, while the most complex model explicitly includes diatoms and the formation of fast sinking diatom aggregates and cysts under silicate limitation. We carried out a variational optimization and error analysis for the biological parameters of all three models, and compared their ability to replicate the observations. The observations were sufficient to constrain most phytoplankton-related model parameters to accuracies of better than 15%. However, the lack of zooplankton observations leads to large uncertainties in model parameters for grazing. The simulated vertical carbon flux at 100 m depth is similar between models and agrees well with available observations, but at 600 m the simulated flux is much larger for the model with diatom aggregation. While none of the models can be formally rejected based on their misfit with the available observations, the model that includes export by diatom aggregation has slightly better fit to the observations and more accurately represents the mechanisms and timing of carbon export based on observations not included in the optimization. Thus models that accurately simulate the upper 100 m do not necessarily accurately simulate export to deeper depths.

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Net community production and export from Seaglider measurements in the North Atlantic after the spring bloom

Journal of Geophysical Research Oceans ◽

10.1002/2014jc010105 ◽

2014 ◽

Vol 119 (9) ◽

pp. 6121-6139 ◽

Cited By ~ 19

Author(s):

Matthew B. Alkire ◽

Craig Lee ◽

Eric D'Asaro ◽

Mary Jane Perry ◽

Nathan Briggs ◽

...

Keyword(s):

North Atlantic ◽

Spring Bloom ◽

Net Community Production ◽

The North ◽

The North Atlantic ◽

Community Production

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Timing of migratory baleen whales at the Azores in relation to the North Atlantic spring bloom

Marine Ecology Progress Series ◽

10.3354/meps09349 ◽

2011 ◽

Vol 440 ◽

pp. 267-279 ◽

Cited By ~ 46

Author(s):

F Visser ◽

KL Hartman ◽

GJ Pierce ◽

VD Valavanis ◽

J Huisman

Keyword(s):

North Atlantic ◽

Spring Bloom ◽

Baleen Whales ◽

The North ◽

The North Atlantic

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The carbon balance during the 1989 spring bloom in the North Atlantic Ocean, 47°N, 20°W

Deep Sea Research Part A Oceanographic Research Papers ◽

10.1016/0198-0149(92)90025-o ◽

1992 ◽

Vol 39 (10) ◽

pp. 1707-1725 ◽

Cited By ~ 65

Author(s):

Michael Bender ◽

Hugh Ducklow ◽

John Kiddon ◽

John Marra ◽

John Martin

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

Carbon Balance ◽

Spring Bloom ◽

North Atlantic Ocean ◽

The North ◽

The North Atlantic

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Ocean climate response to anomalous surface buoyancy and momentum fluxes

10.5194/egusphere-egu2020-20822 ◽

2020 ◽

Author(s):

Rene Navarro-Labastida ◽

Riccardo Farneti

Keyword(s):

Heat Flux ◽

North Atlantic ◽

Surface Heat ◽

High Latitudes ◽

Temperature Changes ◽

Ocean Climate ◽

The North ◽

Anomalous Surface ◽

Low Latitudes ◽

The North Atlantic

The aim of the project is to evaluate the response of the global ocean climate to anomalous surface fluxes in terms of ocean heat uptake and circulation changes. All simulations have been performed with the NOAA-GFDL Modular Ocean Model (MOM) version 5. Ocean-only MOM has been integrated toward a near-equilibrium state using as multicentinal initial conditions derivated from a former CORE-I protocol implementation (Griffies et al., 2009). After equilibrium, a restored control simulation has been obtained by a further 70 years of integration while effective total air-sea heat fluxes and freshwater fluxes were stored at daily intervals. A second control simulation has been obtained by the prescription of these storage fluxes. Differences between the restored and prescribed fluxes controls are rather small. Explicit flux sensitivity experiments are proposed by the Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) in which prescribed surface flux perturbations are applied to the ocean in separated simulations (Gregory et al., 2016). Experiments are 70 years long and branch from piControl conditions. Both wind stress and freshwater anomalies implies nearly-to-zero temperature changes in volume mean temperature. Only the last implies a rather small cooling effect after year 50 of integration. In contrast, anomalous heat flux causes significant volume mean temperature changes. Observed total temperature changes are solely determined by the local addition of heat implying vanishing of the redistribution effect in the entire ocean by inter-basin exchanges and vertical mixing. So far, surface heat anomalies produce the most notable zonal-mean change in ocean temperature. Strong positive temperature change is observed along the top ocean while deepening of temperature anomalies occurs at high latitudes in both hemispheres. Both added and redistributed temperature tracers show maxima in the same area. In most cases, both processes are proportionally inverse. Except for the northern ocean, added temperature tracer is roughly limited to the first 1000 m deep. In contrast, redistributed temperature tracer shows the cooling of subtropical areas and the warming of both the tropical and southern ocean. Maximum at the North Atlantic is possibly due to atmosphere-sea feedbacks, while near-surface tropical and subtropical changes are due to redistribution processes. Heat is mainly taken as a passive tracer in the North Atlantic Ocean and along the entire Southern Ocean. Warming up of mid and low latitudes by redistribution processes is due to the weakening of the Atlantic Meridional Overturning Circulation (AMOC). In turn, changes in AMOC are dominated by surface heat flux changes. The reduction of northward heat transport cools down high latitudes near the surface causing low latitudes to warm up.&#160;

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