Annual Forecasts     Print   PDF

	Enlarge Image Figure 1. Multiple nested hydrodynamic model.  The outermost model is the data assimilative North Atlantic HYCOM, which provides open boundary conditions (OBCs) for the shelf-scale ROMS model, which in turn provides OBCs for the innermost Gulf of Maine ROMS model.  The A. fundyense population dynamics model is run only on the innermost grid.  From He et al. (2008). (Dennis McGillicuddy, WHOI)
	Enlarge Image Figure 2. The A. fundyense population dynamics model.  Fundamental to this approach is the concept that the ecosystem in which A. fundyense resides is not explicitly modeled.  This is justified on the basis that, with very few exceptions, A. fundyense constitutes a small fraction of the total phytoplankton species assemblage in the GOM.  As such, it does not materially affect either the ambient nutrient concentrations or predator abundances.  Therefore these “ecosystem effects” can be parameterized through their influence on the vital rates of A. fundyense’s population dynamics.  These vital rates are complex functions of environmental parameters, such as temperature, salinity, light and nutrients in the case of vegetative growth, and temperature, light and an endogenous clock in the case of germination.   All of this takes place in an complex, turbulent, three-dimensional fluid medium, some characteristics of which are evident in the sea surface temperature image on which this schematic is overlaid. (Dennis McGillicuddy, WHOI)
	Enlarge Image Figure 3.  Ensemble members for the 2014 seasonal forecast. (Dennis McGillicuddy, WHOI)
	Enlarge Image Figure 4. Timeline of the first two forecast cycles.  All subsequent cycles have the same format as cycle two, with the transition between forecast and hindcast forcing advancing by one week in each cycle. (Dennis McGillicuddy, WHOI)

Computer models are used to predict the distribution and abundance of the toxic dinoflagellate Alexandrium fundyense in the Gulf of Maine.  These predictions take two forms: (1) a seasonal forecast issued prior to the bloom season, and (2) weekly updates that hindcast the bloom up to that date, and forecast bloom conditions for the coming week.  Both systems utilize a high-resolution (1-3km in the horizontal, 36 vertical layers) model of the region, which is nested in a shelf-wide model spanning the waters from the Carolinas to Nova Scotia, which is in turn nested within a global operational model (Figure 1).  This multiply-nested configuration provides the spatial resolution necessary for this coastal application, making direct use of an operational model to provide the boundary conditions needed for regional domains.

The conceptual basis of the forecast system is that, all other things being equal, the abundance of A. fundyense resting cysts is a first-order predictor of the magnitude of the bloom in the upcoming year.  In a sense, this approach is analogous to techniques used for fisheries management—‘recruitment’ is measured in the autumn by quantifying the abundance of resting cysts, thereby facilitating an estimate of the ‘stock’ of A. fundyense in the subsequent bloom season.   The initial condition, starting March 1 of each year, is that the concentration of A. fundyense motile (vegetative) cells is zero throughout the model domain.  Cells enter the water column via germination, which is computed from the observed distribution of resting cysts and excystment rates based on laboratory measurements.  The population grows as a function of light, temperature, salinity, and nutrient concentration, all of which are also constrained by experimental laboratory results.  Cells are lost from the water column with a temperature-dependent mortality.  All of this takes place in the complex three-dimensional hydrodynamic environment simulated by the model, which continually redistributes the population via transport and mixing (Figure 2).

In advance of each bloom season, a seasonal forecast is computed using the observed cyst abundance and a range of environmental conditions from preceding years.  For example, in 2014 there were ten ensemble members, based on archived hydrodynamic hindcasts for each year, 2004-2013 (Figure 3).  The resulting ensemble forecast provides an estimate of the range of possible outcomes based on recent history, analogous to the “cone of uncertainty” in hurricane forecasting.  Once the season begins, the forecast model is run weekly with forcing from that particular year, using seven-day forecast atmospheric and oceanic boundary conditions.  In each subsequent cycle, the forecast forcing is replaced with “reanalysis” hindcasts, and updated forecast forcing is used for the coming week.  This iterative process takes place for the entire bloom season, from March 1 through August 1 (Figure 4).  At present, the system is operated routinely in an academic setting but transition to operational status within NOAA is currently underway.

For the most recent descriptions of the forecast model see He et al. (2008), Li et al. (2009), and McGillicuddy et al. (2011).  For cyst distributions, see Anderson et al. (2014).

Forecast results for 2006-2015 are available at:

http://omgsrv1.meas.ncsu.edu/GoMaine_Redtide/

The forecast for 2016 can be accessed here.

Anderson, D.M., Keafer, B.A., Kleindinst, J.L., McGillicuddy, D.J., Martin, J.L., Norton,K., Pilskaln, C.H., Smith, J.L., Sherwood, C.R., and B. Butman, 2014. Alexandrium fundyense cysts in the Gulf of Maine: Long-term time series of abundance and distribution, and linkages to past and future blooms. Deep-Sea Research II, 103, 6–26.

He, R., D. J. McGillicuddy, B. A. Keafer, and D. M. Anderson. 2008. Historic 2005 toxic bloom of Alexandrium fundyense in the western Gulf of Maine: 2. Coupled Biophysical Numerical Modeling. Journal of Geophysical Research-Oceans 113: C07040, doi:07010.01029/02008JC004840.

Li, Y., R. He, D. J. McGillicuddy, D. M. Anderson, and B. A. Keafer. 2009. Investigation of the 2006 Alexandrium fundyense Bloom in the Gulf of Maine: In situ Observations and Numerical Modeling. Continental Shelf Research 29: 2069-2082.

McGillicuddy, D. J., D. W. Townsend, R. He, B. A. Keafer, J. L. Kleindinst, Y. Li, J. P. Manning, D. G. Mountain, M. A. Thomas, and D. M. Anderson. 2011. Suppression of the 2010 Alexandrium fundyense bloom by changes in physical, biological, and chemical properties of the Gulf of Maine. Limnology and Oceanography 56: 2411–2426.

News Releases re Seasonal Forecasts

A new robotic sensor deployed by Woods Hole Oceanographic Institution (WHOI) in Gulf of Maine coastal waters may transform the way red tides or harmful algal blooms (HABs) are monitored and managed in New England. A second such instrument will be launched later this spring.

New England is expected to experience a “moderate” red tide this spring and summer, report NOAA-funded scientists studying the toxic algae that cause blooms in the Gulf of Maine. Red tide is caused by an alga Alexandrium fundyense, which produces a toxin that can cause paralytic shellfish poisoning (PSP).  Red tide occurs annually along some portions of the Gulf of Maine coast.  This outlook is similar to the 2012 red tide which was moderate. 

New England is expected to experience a “moderate” regional “red tide” this spring and summer, report NOAA-funded scientists working in the Gulf of Maine to study the toxic algae that causes the bloom. The algae in the water pose no direct threat to human beings, however the toxins they produce can accumulate in filter-feeding organisms such as mussels and clams — which can cause paralytic shellfish poisoning (PSP) in humans who consume them.