Latitudinal variation in seasonal patterns.

<p>Bi-monthly log transformed mean abundance of <i>Calanus finmarchicus</i> (A) and <i>Centropages typicus</i> (B) from 1977–2009 within each region (binned by 2° latitudes) of the US northeast shelf ecosystem. Numbers are individual m⁻³. Warm color (red) represents high abundance and cold color (blue) represents low abundance. Black squares indicate the peak month.</p

Regression analysis for alongshore velocities and the Gulf Stream north wall index (GSNWI).

<p>A: bi-monthly alongshore velocities from satellite altimetry data and GSNWI and B: annual mean velocities and mean GSNWI.</p

Long term changes of <i>Calanus finmarchicus</i> in the study area.

<p>A: entire region, B: Gulf of Maine (GOM), C: Georges Bank (GB), D: Southern New England (SNE) and E: Mid-Atlantic Bight (MAB). The long term trend was estimated from time series of bi-monthly mean abundance in each subregion by removing seasonal variation. Shaded bars represent alternate years.</p

Zooplankton sampling area in the Northeast U.S. continental shelf including the Gulf of Maine (GOM), Georges Bank (GB), Southern New England (SNE) and the estuarine-dominated waters of the Mid-Atlantic Bight (MAB).

<p>The defined path for alongshore current derived from altimeter sea level data (black bar) at 39.3°N.</p

Comparison of satellite altimetry derived alongshore current and measurements from Acoustic Doppler Current Profiler along a spatially close track line.

<p>Shaded bars represent alternate years.</p

Annual peak abundance and time of <i>Centropages typicus</i> in the Gulf of Maine (GOM), Georges Bank (GB), Southern New England (SNE), and Mid-Atlantic Bight (MAB).

<p>A: peak abundance and B: peak time.</p

Bimonthly mean abundance of <i>Calanus finmarchicus</i>, a large subarctic associated copepod in the study area.

<p>A: entire region, B: Gulf of Maine (GOM), C: Georges Bank (GB), D: Southern New England (SNE) and E: Mid-Atlantic Bight (MAB). Red circles represent observed bi-monthly abundance. Solid black lines represent seasonal patterns determined from the univariate time series analysis, which indicate relative changes to the long term trend rather than absolute abundances. Shaded bars represent alternate years.</p

Bimonthly mean abundance of <i>Centropages typicus</i> a small temperate coastal copepod in the study area.

<p>A: entire region, B: Gulf of Maine (GOM), C: Georges Bank (GB), D: Southern New England (SNE) and E: Mid-Atlantic Bight (MAB). Red circles represent observed bi-monthly abundance. Solid black lines represent seasonal patterns determined from the univariate time series analysis, which indicate relative changes to the long term trend rather than absolute abundances. Shaded bars represent alternate years.</p

DataSheet_1_Surface chlorophyll anomalies induced by mesoscale eddy-wind interactions in the northern Norwegian Sea.docx

The substantial productivity of the northern Norwegian Sea is closely related to its strong mesoscale eddy activity, but how eddies affect phytoplankton biomass levels in the upper ocean through horizontal and vertical transport-mixing has not been well quantified. To assess mesoscale eddy induced ocean surface chlorophyll-a concentration (CHL) anomalies and modulation of eddy-wind interactions in the region, we constructed composite averaged CHL and wind anomalies from 3,841 snapshots of anticyclonic eddies (ACEs) and 2,727 snapshots of cyclonic eddies (CEs) over the period 2000-2020 using satellite altimetry, scatterometry, and ocean color products. Results indicate that eddy pumping induces negative (positive) CHL anomalies within ACEs (CEs), while Ekman pumping caused by wind-eddy interactions induces positive (negative) CHL anomalies within ACEs (CEs). Eddy-induced Ekman upwelling plays a key role in the unusual positive CHL anomalies within the ACEs and results in the vertical transport of nutrients that stimulates phytoplankton growth and elevated productivity of the region. Seasonal shoaling of the mixed layer depth (MLD) results in greater irradiance levels available for phytoplankton growth, thereby promoting spring blooms, which in combination with strong eddy activity leads to large CHL anomalies in May and June. The combined processes of wind-eddy interactions and seasonal shallowing of MLD play a key role in generating surface CHL anomalies and is a major factor in the regulation of phytoplankton biomass in the northern Norwegian Sea.</p